Exam 02 Flashcards
Zoom in on Sample A. You will see that this hand sample is composed of a very dark (black) rock that forms the “matrix” or “groundmass.” Embedded within the black rock are beautiful green crystals. The green crystals are referred to as “phenocrysts.” What is the overall texture of this igneous rock?
a. fine-grained (aphanitic)
b. coarse-grained (phaneritic)
c. porphyritic
d. pyroclastic or fragmental
c. porphyritic
Looking at Sample A, how would you classify this igneous rock based on its composition?
a. felsic
b. intermediate
c. mafic
c. mafic
Zoom in on Sample A and investigate the beautiful green mineral phenocryst. Identify the phenocryst mineral.
a. olivine
b. quartz
c. potassium feldspar
d. biotite
a. olivine
Compare Sample A to Sample B.
a. Both Sample A and Sample B are fine-grained (aphanitic) in texture however Sample B has an overall ultramafic composition.
b. Both Sample A and Sample B are porphyritic in texture however Sample B appears to be intermediate in composition.
c. Both Sample A and Sample B are coarse-grained (phaneritic) in texture however Sample A has an overall mafic composition.
d. Both Sample A and Sample B are pyroclastic (fragmental) in texture and as such, their composition cannot be determined by hand sample investigation.
b. Both Sample A and Sample B are porphyritic in texture however Sample B appears to be intermediate in composition.
Sample B displays large plagioclase phenocrysts that are composed of an even amount of both calcium and sodium in their crystalline structure. Thinking of Bowen’s Reaction Series, this would indicate that the overall composition of the rock sample would be _________________________.
a. ultramafic
b. mafic
c. intermediate
d. felsic
c. intermediate
Move on to Sample C. Look at the overall texture, color and the fact that this sample contains “a rock in a rock”! The black, rectangular shaped rock exists as an inclusion in the lighter rock and is referred to as a/an:
a. phenocryst
b. porphyrite
c. pegmatite
d. xenolith
d. xenolith
The texture of Sample C is indicative of two stages of cooling. Both light and dark crystals occur as phenocrysts. If the light mineral crystals are composed of a sodium-rich plagioclase, according to Bowen’s Reaction Series, the dark crystals would most likely be:
a. Olivine
b. Pyroxene (augite)
c. Amphibole (hornblende)
d. Calcite
c. Amphibole (hornblende)
Sample D is an example of a “contact” between two different types of igneous rock. Compare the two rocks. The texture of the dark rock is ________________________; the texture of the light rock is __________________________.
a. fine-grained (aphanitic); glassy
b. coarse-grained (phaneritic); fine-grained (aphanitic)
c. porphyritic; pyroclastic
d. fine-grained (aphanitic); coarse-grained (phaneritic)
d. fine-grained (aphanitic); coarse-grained (phaneritic)
Sample D is an example of a “contact” between two different types of igneous rock. Compare the two rocks. The composition of the dark rock is ________________________; the composition of the light rock is __________________________.
a. ultramafic; mafic
b. mafic; felsic
c. felsic; mafic
d. intermediate; felsic
b. mafic; felsic
Sample D is an example of a “contact” between two different types of igneous rock. Compare the two rocks. Based on texture and composition, the name given to the black rock is ____________________________ while the name given to the light rock is _____________________________.
a. basalt; granite
b. gabbro; rhyolite
c. andesite; diorite
d. calcite; dolomite
a. basalt; granite
Sample E is referred to as a “xenobomb.” The green rock is encased in a black rock. Compare the composition of the two rocks. The green rock is composed almost entirely of one mineral. Identify that mineral.
a. quartz
b. plagioclase
c. pyroxene (augite)
d. olivine
d. olivine
Based on your identification of the green mineral in Sample E, the overall composition of the green rock would _______.
a. be high in silica and low in iron and magnesium
b. be low in silica and high in iron and magnesium
c. have approximately equal amounts of silica, iron, and magnesium
d. contain calcium carbonate and no silica
b. be low in silica and high in iron and magnesium
Based on the overall composition of the green rock in sample E, it would be safe to assume that the green rock originated in _____________________________.
a. outer space
b. the continental crust
c. the upper mantle
d. core
c. the upper mantle
Zoom in and look at Sample F in detail. This igneous rock contains at least 50% of a dark greenish grey mineral that has been identified as calcium rich plagioclase. There is also about an equal amount of a dark greenish black mineral that forms a texture of interlocking crystals with the plagioclase. Thinking of Bowen’s Reaction Series, the dark greenish black mineral would most likely be _________________________.
a. pyroxene (augite)
b. amphibole (hornblende)
c. biotite
d. muscovite
a. pyroxene (augite)
Zoom in and look at Sample F in detail. This igneous rock contains at least 50% of a dark greenish grey mineral that has been identified as calcium rich plagioclase. There is also about an equal amount of a dark greenish black mineral that forms a texture of interlocking crystals with the plagioclase. This overall texture of this sample is _______________________.
a. coarse-grained (phaneritic)
b. porphyritic
c. fine-grained (aphanitic)
d. pegmatitic
a. coarse-grained (phaneritic)
Based on your answers to the previous two questions, Sample F can be identified as ____________________________.
a. peridotite
b. gabbro
c. basalt
d. andesite
b. gabbro
Take a look at sample G. Look at the architecture peeking out to the right in the picture. Cool! Where do you think this picture was taken? Zoom in closely to this sample. It is dominated by three minerals: one pink, one clear and one black. Based on the overall comparison of dark to light minerals, what general composition would you apply to this rock?
a. ultramafic
b. mafic
c. intermediate
d. felsic
d. felsic
Continue examining sample G. What would be the most likely identification given to the peach-colored or pink mineral?
a. plagioclase
b. potassium feldspar
c. muscovite
d. quartz
b. potassium feldspar
Continue your examination of Sample G. This overall texture of this sample is _______________________.
a. coarse-grained (phaneritic)
b. porphyritic
c. fine-grained (aphanitic)
d. pegmatitic
a. coarse-grained (phaneritic)
Based on your answers to the previous three questions, Sample G can be identified as ____________________________.
a. peridotite
b. gabbro
c. granite
d. rhyolite
c. granite
Look at this outcrop of igneous rock seen in Sample H. The layered grey to tan/pinkish colored rock is volcanic tuff. The texture of this rock would be _______________________________.
a. porphyritic
b. glassy
c. pyroclastic/fragmental
d. pegmatitic
c. pyroclastic/fragmental
Let’s keep examining Sample H. The black, rectangular rock is a piece of the pre-existing volcanic rock prior to the eruption. Looking at the scale provided in the photo, what is the specific size/shape classification given to this pyroclastic chunk of black rock? It may be useful to skip ahead and consult Chapter 5’s discussion of the types of pyroclastic materials.
a. ash
b. lapilli
c. block
d. bomb
c. block
Zoom in closely on the black rock in Sample H. In particular, look at the bottom left corner of the rock. It contains quite a few “holes.” What is the specific name given to these “holes”?
a. pyroclasts
b. phenocrysts
c. porphyroblasts
d. vesicles
d. vesicles
Sample IA and IB tell an interesting story of the cooling history of lava. Sample IB is composed of basalt. Sample IA was originally basalt but has since been lightly metamorphosed during the formation of the Appalachian Mountains, however, still retains some of its original igneous structure. These rocks would be classified as ________________________________.
a. intrusive
b. extrusive
c. plutonic
d. pegmatitic
b. extrusive
The distinctive structure seen in these Samples IA and IB (from two different angles) is/are ____________________________ and is caused by ____________________________.
a. columnar jointing; cooling and contraction of the freshly crystallized volcanic rock
b. lava tubes; quick cooling of lava forming a pipe-like conduit for the still molten rock material
c. pillow lavas; lava erupting underwater
d. pahoehoe lava; cooling of low viscosity lava with a “ropey” texture
a. columnar jointing; cooling and contraction of the freshly crystallized volcanic rock
Be a field geologist! Approach the Sample J outcrop with our hand lens. Zoom in on the rock to determine its overall texture and composition. The occurrence of the pink potassium feldspar coupled with the observed texture would most likely indicate that the rock is ________________________.
a. diorite
b. andesite
c. granite
d. rhyolite
c. granite
Sample K is an interesting rock with a varied cooling history. Zoom around and check out phenocrysts of quartz, potassium feldspar and a dark mineral that is most likely hornblende. There are also a few small, angular pink fragments that are pieces of pre-existing rock. Based on the overall color and identification of the phenocryst minerals, what would be composition of this rock?
a. ultramafic
b. mafic
c. intermediate
d. felsic
d. felsic
Now evaluate the texture of sample K. What is the texture of this igneous rock?
a. fine-grained (aphanitic)
b. coarse-grained (phaneritic)
c. porphyritic
d. pyroclastic or fragmental
d. pyroclastic or fragmental
The best name for sample K, which erupted 760,000 years ago in eastern California, would be…
a. granite
b. rhyolite
c. welded tuff
d. lapilli
c. welded tuff
Compare Samples L1 and L2. These are both products of volcanic eruptions collected from the ground around the volcanoes. Based entirely on the size of the particles in the samples, which sample would have been collected closer to the eruptive site of the volcano? It may be useful to skip ahead and consult Chapter 5’s discussion of the types of pyroclastic materials.
a. L1
b. L2
a. L1
Keep going with your comparison of Samples L1 and L2. These products of volcanic eruption are referred to generally as ________. It may be useful to skip ahead and consult Chapter 5’s discussion of the types of pyroclastic materials.
a. porphyoblastic material
b. phenocrysts
c. pyroclastic material
d. plutonic material
c. pyroclastic material
One last question about Samples L1 versus Sample L2. Based entirely on the size of the particles in the samples, Sample L1 would be classified as ______________________ while Sample L2 would be classified as ________________________. It may be useful to skip ahead and consult Chapter 5’s discussion of the types of pyroclastic materials.
a. lapilli, ash
b. blocks, bombs
c. volcanic, extrusive
d. plutonic, intrusive
a. lapilli, ash
Examine Sample M. What could I say about this sample based on its observable characteristics?
a. I could say that it is volcanic in origin and felsic in composition.
b. I could say that it is plutonic in origin and felsic in composition.
c. I could say that it is volcanic in origin and intermediate in composition.
d. I could say that it is plutonic in origin and intermediate in composition.
a. I could say that it is volcanic in origin and felsic in composition.
Compare Sample N with Samples L1 and L2. All of these samples represent an environment of formation classified as _______________________________.
a. volcanic
b. plutonic
c. intrusive
d. under water
a. volcanic
Sample N is an example of a/an __________. It may be useful to skip ahead and consult Chapter 5’s discussion of the types of pyroclastic materials.
a. andesite
b. volcanic bomb
c. ashfall
d. volcanic block
b. volcanic bomb
Examine Sample O. Its texture, characteristic “salt and pepper” color and almost equal quantities of both dark and light minerals would indicate that it is ____________________________.
a. gabbro
b. basalt
c. diorite
d. granite
b. basalt
Sample O’s texture indicate that it is ____________________________.
a. volcanic in origin
b. plutonic in origin
c. extrusive in origin
d. pyroclastic in origin
b. plutonic in origin
Investigate Sample P. It is difficult to determine its actual composition without a little more information however its dark grey color would most likely eliminate a _______________________ composition.
a. felsic
b. intermediate
c. mafic
d. basaltic
a. felsic
Sample P contains quite a few holes. These holes indicate that as the lava was cooling, exsolved gas became trapped and formed air pockets called _______________________.
a. pyroclasts
b. vesicles
c. glass
d. lava bubbles
b. vesicles
Compare Sample P to Sample Q. They are similar in color however they have a different texture. Which options would represent sample P, which represent Sample Q, and which represent neither Sample P or Q?
a. Vesicular
b. Porphyritic
c. Two stages of cooling
d. Strictly volcanic
e. Some intrusive and some extrusive characteristics
f. Strictly intrusive
Sample P = a, d
Sample Q = b, c, e
Neither sample = f
Zoom in to look at a close-up view of the large mineral crystals in Sample Q . These are obviously three different minerals. If the light colored mineral is a sodium-rich plagioclase, identify the other two phenocryst minerals (the brown platy one and the black prisms) ; keep Bowen’s Reaction Series in mind. Additional characteristics for the first mineral: it occurs in flexible sheets and has one perfect direction of cleavage. Additional characteristics for the second mineral: it is black and shiny and has two planes of cleavage that do not intersect at 90 degrees.
These two minerals are _______ and _________.
a. olivine and pyroxene (augite)
b. pyroxene (augite) and amphibole (hornblende)
c. biotite and amphibole (hornblende)
d. quartz and muscovite
c. biotite and amphibole (hornblende)
Zoom around and look at the different varieties of Sample R. They are all the same rock type but can display some different colors. Zoom in on some of the curved, ribbed fracture surfaces. This is typical of how this rock breaks. Identify this volcanic rock.
a. andesite
b. basalt
c. scoria
d. obsidian
d. obsidian
What name is applied to the type of breakage you observed in sample set R?
a. one “perfect” plane of cleavage
b. two planes of cleavage that intersect at a 90 degree angle
c. two planes of cleavage that do not intersect at a 90 degree angle
d. conchoidal fracture
d. conchoidal fracture
How would you describe the cooling history and characteristic texture of Sample R?
a. Sample R cooled very quickly and therefore has a coarse-grained (phaneritic) texture.
b. Sample R cooled very slowly and therefore has a fine-grained (aphanitic) texture.
c. Sample R cooled virtually instantaneously (or else the lava was very dry) and therefore has a glassy texture.
d. Sample R cooled in two stages and therefore displays a porphyritic texture.
c. Sample R cooled virtually instantaneously (or else the lava was very dry) and therefore has a glassy texture.
Examine Sample S and spend some time examining some of its larger clasts. What type of texture characterizes this sample?
a. porphyritic
b. pyroclastic
c. coarse-grained (phaneritic)
d. fine-grained (aphanitic)
b. pyroclastic
What would be the best name for sample S?
a. granite
b. basalt
c. porphyritic andesite
d. welded tuff
e. volcanic breccia
f. laharite
e. volcanic breccia
Interpret Sample S. What process(es) produce this type of rock? It may be useful to skip ahead and consult Chapter 5’s discussion of the types of pyroclastic materials as well as the discussion of volcanic hazards.
a. This is an intrusive rock so the magma never erupted. It likely cooled slowly underground.
b. This type of rock likely represents a high temperature, low viscosity magma erupting with low explosivity. An effusive eruption, it flooded the landscape.
c. This type of rock likely represents an underwater eruption associated with the formation of pillow lava.
d. This rock likely formed from a volcanic mudflow (lahar) which typically represents high explosivity mixed with a ready supply of water.
d. This rock likely formed from a volcanic mudflow (lahar) which typically represents high explosivity mixed with a ready supply of water.
The intrusive and extrusive, intermediate composition igneous are:
a. gabrro and basalt
b. diorite and andesite
c. granite and rhyolite
d. quartz and feldspar
b. diorite and andesite
The intrusive and extrusive, mafic igneous rocks are:
a. gabbro and basalt
b. diorite and andesite
c. granite and rhyolite
d. quartz and feldspar
a. gabbro and basalt
Igneous rock composition however is dictated by the amount of silica present in the rock. High silica content will result in a __________________________ composition.
a. dark
b. felsic
c. mafic
d. intermediate
b. felsic
The intrusive and extrusive, felsic igneous rocks are:
a. gabbro and basalt
b. diorite and andesite
c. granite and rhyolite
d. quartz and feldspar
c. granite and rhyolite
Dikes are igneous intrusive bodies that form ________ to bedding.
a. parallel
b. horizontal
c. perpendicular
d. underneath
c. perpendicular
When magma solidifies (cools) it hardens to form an igneous rock. Igneous rocks like all other rocks can be classified in terms of their texture and composition. Texture for igneous rocks can be classified as either ________________________ or _________________________. Each of these textures is determined by how fast or slow the magma cooled.
a. hot, cold
b. intrusive, extrusive
c. mafic, felsic
d. coarse-grained, phaneritic
b. intrusive, extrusive
Igneous rock composition is categorized as:
a. Light, medium, dark
b. Mafic (basaltic), intermediate (andesitic), felsic (granitic)
c. Intrusive, extrusive, plutonic
d. Basaltic, mafic, gabbro
b. Mafic (basaltic), intermediate (andesitic), felsic (granitic)
Igneous rocks can have special textures. For example, a porphyritic texture has two different minerals sizes which is indicates two different cooling rates.
True or False
True
Poorly textured rocks specifically porphyritic texture with two distinct mineral sizes (large and small crystals) indicates two-stage cooling process with slow cooling followed by rapid cooling.
___________ involves the changing of magma composition by the removal of denser early-formed ferromagnesian minerals by crystal settling
a. magma mixing
b. differentiation
c. assimilation
d. partial melting
b. differentiation
The 3 major components of magma include:
a. An intrusive, an extrusive, and volatile component
b. A mafic, a felsic, and an intermediate component
c. An earth, a water, and a wind component
d. A liquid , a solid, and a gaseous component
d. A liquid , a solid, and a gaseous component
What is the difference between “magma” and “lava”?
a. magma contains some solids but lava is completely liquid
b. lava contains some solids but magma is completely liquid
c. magma is more viscous (thicker) than lava
d. they are both molten rock material, but magma is below the land surface and lava is above the land surface.
d. they are both molten rock material, but magma is below the land surface and lava is above the land surface.
What are the three major components of all magma?
a. solid, melt, and organic matter
b. solid, melt, and volatiles
c. melt, gasses and volatiles
d. solids, rocks, and melt
b. solid, melt, and volatiles
An igneous rock/magma with a mafic composition will be characterized by __________.
a. coarse-grained mineral crystals
b. fine-grained mineral crystals
c. silica-rich (Si-rich) minerals
d. abundant ferromagnesian (Fe/Mg-rich) minerals
d. abundant ferromagnesian (Fe/Mg-rich) minerals
An igneous rock with an aphanitic texture will be characterized by __________.
a. minerals that can only be observed with the aid of a microscope.
b. minerals that can be seen with the naked eye.
c. abundant visicles (gas bubbles) in the rock.
d. a smooth glassy texture
a. minerals that can only be observed with the aid of a microscope.
All of the following are means of melting rocks on earth except __________.
a. addition of organic matter to rock
b. increase temperature of rock
c. addition of water to rock
d. decrease pressure of rock
a. addition of organic matter to rock
Materials extruded by eruptions are categorized as:
a. Lava, gases, and pyroclastics (solid fragments)
b. Silica content, dissolved gases, and magma mixing
c. Cinder, composite, and shield
d. Vent, crater, and caldera
a. Lava, gases, and pyroclastics (solid fragments)
Extrusive igneous rocks are coarse grained.
True or False
False
The name for a volcanic mudflow is:
a. Vent
b. Crater
c. Caldera
d. Lahar
d. Lahar
A fluid’s resistance to flow is called:
a. Viscosity
b. Energy
c. Carbon Dioxide
d. Silica
a. Viscosity
Intrusive, phaneritic, and glassy are all terms that describe volcanic textures.
True or False
False
Intrusive describes the environment in which rock forms and is not a texture itself.
Glassy and phaneritic can be used to describe igneous rock textures.
_________________________ : broad, gently sloping, composed of solidified lava flows, and often contain lava tubes.
a. Composite volcano
b. Cinder cone volcano
c. Shield volcano
d. Volcanic dome
c. Shield volcano
Three volcanic landforms are vents, craters, and calderas.
True or False
True
The runniest/fastest/least viscous type of lava is:
a. a’a
b. pahoehoe
c. andesite
d. rhyolite
b. pahoehoe
Violence of eruptions is controlled by both:
Select all that apply
a. Convection
b. Silica Content
c. Dissolved Gases
d. Magma Mixing
b. Silica Content
c. Dissolved Gases
_________________________ is small, steeply sloping, and composed of a pile of loose cinders.
a. Composite volcano
b. Cinder cone volcano
c. Shield volcano
d. Volcanic dome
b. Cinder cone volcano
________ is a material’s resistance to flowing.
a. composition
b. texture
c. viscosity
d. volatiles
c. viscosity
________ is the name given to the mix of pulverized rock, lava fragments, and ash erupted from a volcano.
a. lapilli
b. pahoehoe
c. aa
d. pyroclastic materials
d. basalt
e. extrusive
d. pyroclastic materials
What is the name for the holes in this basalt? How did they form?
a. phenocrysts; they crystallized from the magma underground
b. vesicles; they form when the lava degasses upon eruption, forming bubbles
c. lapilli; they represent little craters from another eruptive event somewhere nearby
d. dikes; they form when new magma intrudes into old rock, then drains away, leaving a hole
b. vesicles; they form when the lava degasses upon eruption, forming bubbles
Volcanoes associated with a subduction zone are likely to be _________________.
a. cinder cones
b. shield volcanoes
c. composite volcanoes
d. fissure eruptions
c. composite volcanoes
Pillow basalts are most likely to be associated with a(n) __________________________.
a. seamount
b. dome
c. caldera
d. neck
a. seamount
Lavas erupting from composite volcanoes are generally ________-rich, making them very viscous.
a. sulfur
b. silica
c. mercury
d. iron
b. silica
What is the driving force behind pyroclastic flows?
a. Water
b. Compositional change
c. Temperature inversion
d. Gravity
d. Gravity
Flood basalts would have _________________ viscosity.
a. high
b. medium
c. low
c. low
A lahar is a volcanic mudflow.
True or False
True
Divergent plate boundaries are where we find most felsic volcanism.
True or False
False
Divergent plate boundaries are where we find most mafic volcanism. Felsic volcanism is more common at convergent boundaries.
Partial melting of andesite generates a magma with an ultramafic composition.
True or False
False
Kilauea is a volcano created by intraplate (hot spot) volcanism.
True or False
True
There greatest hazard associated with volcanoes is the risk of getting caught up in a lava flow.
True or False
False
The least fertile type of soil found in the tropics is:
a. calcitic
b. loam
c. organic-overloaded
d. laterite
d. laterite
___________________describes the process of chemically active oxygen from the atmosphere combining with a rock surface material resulting in the formation of iron oxides.
a. Oxidation
b. Chemical weathering
c. Dissolution
d. Spheroidal weathering
a. Oxidation
The controls on soil formation include, parent material, climate, plants and animals, ___________, and __________________.
a. quartz content, and water
b. topography, and time
c. feldspar formation, and quartz content
d. water, and temperature
b. topography, and time
Which is not a process of mechanical weathering?
a. Frost wedging
b. Dissolution
c. Exfoliation
d. Wave pounding
b. Dissolution
________________________ occurs where rock has been rounded by weathering from an initial blocky shape.
a. Oxidation
b. Chemical weathering
c. Dissolution
d. Spheroidal weathering
d. Spheroidal weathering
___________________ is the decomposition of rock from exposure to atmospheric gases (oxygen, water vapor and carbon dioxide)
a. Mechanical/physical weathering
b. Chemical weathering
c. Weathering
d. Erosion
b. Chemical weathering
_____________________ is the physical picking up of rock particles by water, ice, or wind.
a. Mechanical/physical weathering
b. Chemical weathering
c. Weathering
d. Erosion
d. Erosion
_______________________is the group of destructive processes that change physical and chemical character of rocks at or near Earth’s surface.
a. Mechanical/physical weathering
b. Chemical weathering
c. Weathering
d. Erosion
c. Weathering
____________________ is the physical disintegration via frost action, pressure-release fracturing, plant growth, burrowing animals, salt wedging, thermal cycling.
a. Mechanical/physical weathering
b. Chemical weathering
c. Weathering
d. Erosion
a. Mechanical/physical weathering
Soil is a layer of weathered, unconsolidated material on top of bedrock.
True or False
True
What are the chief components making up most clastic sedimentary rocks?
a. quartz and olivine
b. mica and quartz
c. quartz and clay minerals
d. feldspar and clay minerals
e. olivine and clay minerals
c. quartz and clay minerals
What differentiates a conglomerate from a breccia?
a. Conglomerates have angular grains of gravel, indicating a short transport distance.
b. Conglomerates have rounded grains of gravel, indicating a short transport distance.
c. Conglomerates have angular grains of gravel, indicating a long transport distance.
d. Conglomerates have rounded grains of gravel, indicating a long transport distance.
e. Conglomerates are carbonate; breccia is clastic.
d. Conglomerates have rounded grains of gravel, indicating a long transport distance.
____________ is a sandstone with more than 25 percent feldspar, also containing quartz and mica with particles that are poorly sorted and angular.
a. Graywacke
b. Limestone
c. Conglomerate
d. Arkose
e. Quartz sandstone
f. Granite
g. Rhyolite
h. Shale
d. Arkose
Sedimentary rocks are the main family of rocks that contain ____________.
a. phenocrysts
b. porphyroblasts
c. fossils
d. carbon
e. layers
c. fossils
A sedimentary rock that contains a mixture of large and small particles is __________.
a. biogenic
b. poorly sorted
c. oolitic
d. well-sorted
e. well-rounded
b. poorly sorted
Which sedimentary rock is most likely to represent deposition on a beach?
a. Anthracite coal
b. Quartz sandstone
c. Arkose
d. Breccia
e. Oolitic limestone
f. Rock salt
b. Quartz sandstone
Which primary sedimentary structure would indicate exposure to the air?
a. Ooids
b. Graded beds
c. Bedding
d. Reefs
e. Mud cracks
f. Turbidites
e. Mud cracks
____________ is a collective term for all of the chemical, physical, and biological changes that take place after sediments are deposited and during and after lithification.
a. Weathering
b. Erosion
c. Diagenesis
d. Lithification
e. Compaction
f. Cementation
c. Diagenesis
Which of the following is a soft, black coal that forms when organic matter (plants) experience significant burial and compaction?
a. Anthracite
b. Bituminous
c. Lignite
d. Peat
e. Ferns
b. Bituminous
The minerals gypsum and halite form in lake or lagoon environments that are subject to arid conditions. Which variety of chemical sedimentary rock do they form?
a. clastic
b. limestone
c. chert
d. evaporites
e. coal
d. evaporites
What are the two most common forms of weathering?
a. chemical and material
b. material and physical
c. physical and chemical
d. physical and biological
c. physical and chemical
The removal of charged ions from a solid material by interaction with a polarized water molecule is termed __________.
a. dissolution
b. hydrolysis
c. oxidation
d. frost wedging
a. dissolution
Half Dome in Yosemite National Park is a good example of which type of weathering?
a. sheeting
b. frost wedging
c. salt wedging
d. biological weathering
a. sheeting
The washing out of fine particles in a soil profile by the action of the downward percolation of water from the surface is termed __________.
a. removal
b. leaching
c. dissolution
d. eluviation
d. eluviation
All soil must contain all of the following except _________.
a. water
b. mineral matter
c. animal matter
d. organic matter
c. animal matter
Which horizon contains the highest percentage of organic matter?
a. E horizon
b. O horizon
c. A horizon
d. C horizon
b. O horizon
When water reacts with a mineral such as feldspar to break it down and make new minerals such as clay (kaolinite), _____________________ is taking place.
a. dissolution
b. hydrolysis
c. oxidation
d. sheeting
b. hydrolysis
What type of soil is typically found in tropical locations?
a. ultisol
b. alfisol
c. aridisol
d. oxisol
d. oxisol
These types of soil are common in the western United States and can contain salts due to the incomplete removal of solubles in the soil profile.
a. ultisol
b. alfisol
c. aridisol
d. oxisol
c. aridisol
What is responsible for most of the soil erosion occurring in the United States?
a. flowing water
b. wind
c. suburban development
d. dissolution
a. flowing water
One means of preventing soil erosion is __________.
a. soil replenishment
b. regular irrigation
c. salt treatments
d. contour planting
d. contour planting
What was the cause of the 1930’s Dust Bowl?
a. urban sprawl due to western migration people
b. transformation of semiarid grasslands into agricultural lands
c. massive flooding during the 1930’s
d. Severe winter storms and the freezing of the topsoil.
b. transformation of semiarid grasslands into agricultural lands
Why are soils in tropical rain forests generally not suitable for agriculture?
a. they lack sufficient nutrients
b. they are too hot
c. they are too wet
d. they have too much organic matter
a. they lack sufficient nutrients
The rate of chemical weathering has been artificially accelerated in several portions of the eastern United States by this phenomenon.
a. intense agricultural usage
b. overdevelopment of urban areas
c. an increase in hurricane frequency
d. acid rain from the burning of fossil fuels
d. acid rain from the burning of fossil fuels
Mechanical weathering can increase the rate of chemical weathering by ___________.
a. increasing the volume of a rock
b. decreasing the exposed surface area of a rock
c. increasing the exposed surface area of a rock
d. decreasing the melting temperature of a rock
c. increasing the exposed surface area of a rock
The complex process whereby silicate minerals such as feldspar are broken down to make clay minerals by reacting with water molecules is ___________________________________.
a. dissolution
b. oxidation
c. sheeting
d. hydrolysis
d. hydrolysis
Highly weathered rock material is referred to as __________.
a. soil
b. pluton
c. laccolith
d. regolith
d. regolith
Rates of chemical weathering are fastest in regions characterized by __________.
a. high temperatures and high humidity
b. high temperatures and low humidity
c. low temperatures and high humidity
d. low temperatures and low humidity
a. high temperatures and high humidity
Topsoil is composed of which soil horizons?
a. B and C horizons
b. E and B horizons
c. A and E horizons
d. O and A horizons
d. O and A horizons
Examine sample A.
What is the sorting of sample A?
a. well sorted
b. moderately sorted
c. poorly sorted
c. poorly sorted
Examine sample A.
What is the grain roundness of sample A?
a. very angular
b. subangular
c. subround
d. well-rounded
b. subangular
Examine sample A.
What is the composition of sample A? (What minerals is it made of?)
a. rock fragments
b. quartz grains
c. feldspar grains
d. clay
b. quartz grains
Name sample A:
a. breccia
b. conglomerate
c. quartz sandstone
b. conglomerate
Think about the characteristics of sample A, and offer an interpretation for the depositional setting (consult the figures in the above PDF for examples/reference) where it would have formed. Your interpretation should be consistent with the physical characteristics that you have noted for the sample.
a. evaporating playa lake
b. hot springs
c. bog or swamp
d. glacier
e. debris at base of cliff / alluvial fan
f. river channel
g. river floodplain
f. river channel
What is the sorting of sample B?
a. well sorted
b. moderately sorted
c. poorly sorted
c. poorly sorted
What is the grain roundness of sample B?
a. very angular
b. subangular
c. subround
d. well-rounded
a. very angular
What is the composition of sample B? (What minerals is it made of?)
a. rock fragments (with hematite cement)
b. quartz grains (with hematite cement)
c. feldspar grains (with hematite cement)
d. clay (with hematite cement)
b. quartz grains (with hematite cement)
Name sample B.
a. breccia
b. conglomerate
c. quartz sandstone
a. breccia
Think about the characteristics of sample B, and offer an interpretation for the depositional setting:
a. evaporating playa lake
b. hot springs
c. bog or swamp
d. glacier
d. glacier
Examine sample C.
Sample C is a quartz sandstone with red claystone “rip-up” clasts. The red color in the mudstone is due to oxidation of iron in the mud. This implies a depositional setting (sedimentary environment) that was rich in free oxygen.
Given that sand is deposited under moderately-energetic current conditions and clay is deposited in low-energy water (i.e., still water), then what does the presence of the claystone “rip-up” clasts surrounded by sandstone tell you about how water energy must have changed at this location when these sediments were deposited (i.e., before they were lithified to make sedimentary rock)?
a. It indicates that the energy / strength of the water currents must have stayed the same over time.
b. It indicates that the energy / strength of the water currents must have decreased over time.
c. It indicates that the energy / strength of the water currents must have increased over time.
c. It indicates that the energy / strength of the water currents must have increased over time.
The presence of claystone “rip-up” clasts in a sandstone formation indicates that there was a change in the sedimentary environment where deposition occurred. Rip-up clasts are fragments of weaker sedimentary layers that have been eroded and redeposited by stronger currents into a different layer.
In this case, the claystone (mudstone) was originally deposited in a low-energy water environment, while the sandstone was deposited under moderately-energetic current conditions. The fact that the claystone was ripped up and included in the sandstone means that there was an increase in water current energy after the deposition of the claystone but before the lithification of both layers.
Examine sample C.
There is a prominent sedimentary structure to be seen in this sample. Identify this primary sedimentary structure.
a. raindrop impressions
b. graded bed(s)
c. current ripple marks (also called “asymmetrical ripple marks”)
d. cross-bedding
d. cross-bedding
Present in Sample C, the major structure is formed by rather distinct diagonal layers that have alternating colored bands. That is, they are not in contact with the horizontal plane of the bed and thus deposited as a result of currents or directional flow.
The directional arrangement of inclined layers known as bedding plane supports a category known as cross-bedding, which results from sediment transport in current settings such as rivers or sand dunes.
Cross-bedding is obtained when sediment is being laid down by moving water or wind in areas that currents alternate. The forests which develop an inclination toward the GM are individual episodes of sediment deposition. It forms the layers which are inclined as seen in Sample C which results from rivers channel, deltas or deserts setting. The discontinuous bands could be due to differences in grain size, composition of the flow or the nature of the flows within the associated fans.
Eliminate other types of sedimentary structures
Ripple Marks: Usually less extensive, irregularities in the form of waves created by oscillatory or linear currents
Mudcracks: Happen in loans like clay and the surface forms polygons.
Flutes or Flute Casts: Which are unlike the continuous layering that has been observed here and are formed by the scouring action in turbidity currents.
Trace Fossils: Lack of biological activity such as burrows or tracks can similarly not be observed in this particular sample.
Explanation:
First, the diagonal orientation of the layers, second, the absence of such morphological indicators as waviness, jointing or organic traces distinguish the structure in question as cross-bedding as opposed to ripple marks, mudcracks or inclusions.
Interpret sample C.
Based on the sedimentary structure you identified in the previous question, what interpretive statement can you make about the conditions under which this sediment was deposited?
a. It must have been on the land.
b. It must have been exposed to the air.
c. It must have had flowing currents of water.
d. It must have been deposited in a swampy environment with stagnant water.
e. It must have been in a shallow water environment where waves could reach the bottom.
f. It must have been in the deep ocean, deposited by turbidity currents.
c. It must have had flowing currents of water.
Take another look at the sedimentary structure in sample C.
Which way was the water moving when this sedimentary structure formed?
a. from left to right
b. from right to left
b. from right to left
Take another look at the sedimentary structure in sample C.
Based on the way we understand this sedimentary structure to form, is this sample right-side-up or up-side-down?
a. right-side-up
b. up-side-down
a. right-side-up
Sample D is a graywacke sandstone. Two views are provided: On the left, an original view. On the right, the sample has been flipped and cut into four pieces. Each of the pieces has been rotated around a vertical axis (like looking at the face of a slice of bread). The dark gray color (particularly of the finer-grained portion) is indicative of high levels of organic carbon and dark clay (with reduced iron).
What does this implies a depositional setting (sedimentary environment) in terms of its oxygen levels?
a. It indicates that the depositional setting was relatively low in free oxygen.
b. It indicates that the depositional setting was relatively high in free oxygen.
a. It indicates that the depositional setting was relatively low in free oxygen.
Examine sample D.
There is a prominent sedimentary structure to be seen in this sample. Identify this primary sedimentary structure.
a. cross-bedding
b. bimodal cross-bedding
c. wave ripple marks (also called “symmetrical ripple marks” or “oscillation ripple marks”)
d. mudcrack(s) (also called dessication cracks)
c. wave ripple marks (also called “symmetrical ripple marks” or “oscillation ripple marks”)
or could be a. cross-bedding
Interpret sample D.
Based on the sedimentary structure you identified in the previous question, what interpretive statement can you make about the conditions under which this sediment was deposited?
a. It must have been on the land.
b. It must have been exposed to the air.
c. It must have had flowing currents of water.
d. It must have been deposited in a swampy environment with stagnant water.
e. It must have been in a shallow water environment where waves could reach the bottom.
c. It must have had flowing currents of water.
Take another look at the sedimentary structure in sample D.
Based on the way we understand this sedimentary structure to form, is the original sample (i.e., the one at the left side of the screen) right-side-up or up-side-down?
a. right-side-up
b. up-side-down
b. up-side-down
Examine the loose sand samples E, F, G, H. Each is displayed in a petri dish 9 cm in diameter.
Which of the sand samples is dominated by ooids?
Sample E
Examine the loose sand samples G, H, I, and J. Each is displayed in a petri dish 9 cm in diameter.
Which of the sand samples is dominated by olivine?
Sample I
Examine the loose sand samples E, F, G, H. Each is displayed in a petri dish 9 cm in diameter.
Which of the sand samples is dominated by coarse quartz sand?
Sample F
Examine the loose sand samples G, H, I, J. Each is displayed in a petri dish 9 cm in diameter.
Which of the sand samples is dominated by fine quartz sand stained with iron oxide?
Sample J
Compare the loose sand samples G and H.
Which of the 2 sand samples is is derived from rocks with a significant quartz content?
Sample G because it is has sand that is lighter due to its SiO2 content.
Which of the sand samples is most likely from Hawaii?
(Recall that Hawaii is a basaltic volcanic island.)
Sample I
Hawaii does not have continental source of quartz sand like mainland beaches, the sands are made up from volcanic materials and marine sediments
Which of the sand samples is most likely from Virginia Beach, Virginia?
Sample F because Virginia Beach sand is made up of fine-grained quartz.
Which of the sand samples is most likely from the Bahamas?
Sample E
Sand in Bahamas is typically bright or off-white in hue due to the high concentration of calcium carbonate that gives a light appearance. The fine-grained texture has small smooth to touch which feels like soft powder. The mineral calcium carbonate made from coral, shells, and carbonate-rich organism skeletal remains. This sand is primarily marine origin, found nearby waters.
Windblown sand is typically finer-grained, better-sorted, and more well-rounded than water-transported sand.
Bearing this in mind, which of the sand samples is most likely from sand dunes in Dubai?
Sample J
Sand dunes have higher silt content of minerals where as the beach sand has higher calcareous content due to marine organisms with shells.
Compare samples K and L.
Both would fizz if you applied acid to them. Both contain fossils. However, there are some key differences to be noted.
Based on color, which specimen was deposited under higher-oxygen conditions?
Sample K
Specimens deposited under higher-oxygen conditions will typically appear pink or red due to the presence of hematite (Fe2O3).
Lower oxygen conditions would appear gray or greenish due to presence of minerals like magnetite (Fe3O4) or pyrite (FeS2).
Compare samples K and L.
Both show aquatic organisms. However, one shows organisms that live in freshwater (lakes, rivers), while the other shows organisms that live in the ocean (marine water).
Which sample was deposited in marine (oceanic) conditions?
Sample L
Original rational was that sample K would be correct because Low oxygen indicates darker colors and lighter colors indicating higher oxygen environments - but that was incorrect and the answer is sample L.
Examine sample K. Bear in mind that it would fizz if you applied hydrochloric acid to it.
Name sample K.
a. micrite
b. oolitic limestone
c. travertine
d. dolostone
a. micrite
Examine sample L. Bear in mind that it would fizz if you applied hydrochloric acid to it.
Name sample L.
a. fossiliferous limestone
b. oolitic limestone
c. travertine
d. dolostone
a. fossiliferous limestone
You have now identified both samples K and L.
Sample K = Micrite
Sample L = Fossiliferous limestone
Both are fossil-bearing, but only one was “fossiliferous limestone.” What appears to be the critical variable that distinguishes “fossiliferous limestone” from a massive limestone like micrite that happens to have a fossil or two in it?
a. Fossiliferous limestones must be dark-colored.
b. Fossiliferous limestones must be dominated by fossils: the fossils must make up a significant volume of the rock itself. In other words, the rock is defined by it’s prodigious fossil content.
b. Fossiliferous limestones must be dominated by fossils: the fossils must make up a significant volume of the rock itself. In other words, the rock is defined by it’s prodigious fossil content.
Compare samples M and N.
Both show fossils. However, one shows organisms that live on land, while the other shows organisms that live in the ocean (marine water).
Which sample was deposited in marine (oceanic) conditions?
a. M
b. N
b. N
Examine samples M and N again.
Both show fossils. However, one shows relatively recent organisms, while the other shows relatively ancient organisms. See the geologic time scale in the attached reference figures/tables PDF. Find the closest match in the diagram for the fossils you see in the sedimentary rock samples.
How old is sample M?
a. Jurassic
b. Triassic
c. Cretaceous
d. Pennsylvanian
e. Paleogene
e. Paleogene
Examine samples M and N again.
Both show fossils. However, one shows relatively recent organisms, while the other shows relatively ancient organisms. See the geologic time scale in the attached reference figures/tables PDF. Find the closest match in the diagram for the fossils you see in the sedimentary rock samples.
How old is sample N?
a. Mississippian
b. Devonian
c. Silurian
d. Ordovician
b. Devonian
Examine sample O. It would fizz if you applied hydrochloric acid to it.
Name sample O.
a. fossiliferous limestone
b. chalk
c. micrite
d. oolitic limestone
a. fossiliferous limestone
Sample O was photographed in west Texas. It is Cretaceous in age (145-65 million years old). What does this imply about the past? Interpret this sample.
a. During the Cretaceous, west Texas was below sea level.
b. During the Cretaceous, west Texas was a rift valley.
c. During the Cretaceous, west Texas was experiencing an orogeny.
d. During the Cretaceous, west Texas was a spot where rivers were flowing strongly through their main channels, and occasionally flooding their floodplains with mud.
a. During the Cretaceous, west Texas was below sea level.
Think about the characteristics of sample O, and offer an interpretation for the depositional setting where it would have formed. Your interpretation should be consistent with the physical characteristics that you have noted for the sample.
a. shallow sea (clastic sediment)
b. shallow sea (carbonate bank)
c. carbonate reef
b. shallow sea (carbonate bank)
Examine samples P and Q.
P shows a quartet of small rock samples, each a few centimeters long. Originally, they were collected in West Virginia.
Q is an outcrop in West Virginia, a few miles from where the samples of P were collected.
Both are the same geologic formation (or geologic unit). Both would fizz if you first crushed them up to powder, and added hydrochloric acid to that powder.
Name the sedimentary rock that makes up both samples P and Q.
a. oolitic limestone
b. travertine
c. dolostone
c. dolostone
Examine sample P.
There is a prominent sedimentary structure to be seen in this sample. Identify this primary sedimentary structure.
a. raindrop impressions
b. graded bed(s)
c. current ripple marks (also called “asymmetrical ripple marks”)
d. cross-bedding
e. salt cast(s) (preserved cubic shapes of halite crystals, now formed from sedimentary rock)
e. salt cast(s) (preserved cubic shapes of halite crystals, now formed from sedimentary rock)
Examine sample Q.
There is a prominent sedimentary structure to be seen in this sample. Identify this primary sedimentary structure.
a. graded bed(s)
b. current ripple marks (also called “asymmetrical ripple marks”)
c. cross-bedding
d. bimodal cross-bedding
e. mudcrack(s) (also called dessication cracks)
e. mudcrack(s) (also called dessication cracks)
Think about the characteristics of samples P and Q, and offer an interpretation for the depositional setting (sedimentary environment; (Consult the figures in the above PDF for examples/reference) where they would have formed. Your interpretation should be consistent with the physical characteristics that you have noted for the sample.
a. beach
b. shallow sea (clastic sediment)
c. shallow sea (carbonate bank)
d. evaporating playa lake
d. evaporating playa lake
If your interpretation of the depositional setting of samples P and Q is correct (evaporating, supersaturated water), then what other rock type may also be associated with this same formation?
a. chalk
b. micrite
c. rock salt
c. rock salt
Examine sample R. It would not fizz if you applied hydrochloric acid to it.
Name sample R.
a. lithic sandstone
b. graywacke
c. siltstone
d. shale
b. graywacke
Think about the characteristics of sample R, and offer an interpretation for the depositional setting where it would have formed. Your interpretation should be consistent with the physical characteristics that you have noted for the sample.
a. river channel
b. river floodplain
c. shallow sea (carbonate bank)
d. delta (where a river flows into a standing body of water like a lake or the ocean)
e. turbidity current (deep sea fan) on the continental slope
e. turbidity current (deep sea fan) on the continental slope
Examine sample S. Note (a) that it would not fizz if you applied hydrochloric acid to it, and (b) it would break with a conchoidal fracture, and (c) it can scratch glass.
Name sample S.
a. rock gypsum
b. ironstone
c. chert
c. chert
made up of microcrystalline quartz. It is often gray, black, or brown in color, and it can be found in many different depositional settings, including shallow seas, hot springs, and desert environments. Chert will not fizz when you apply hydrochloric acid to it because it does not contain calcium carbonate.
Think about the characteristics of sample S, and offer an interpretation for the depositional setting where it would have formed. Your interpretation should be consistent with the physical characteristics that you have noted for the sample.
Sample S is Chert
a. evaporating playa lake
b. hot springs
c. bog or swamp
d. deep sea (abyssal plain)
d. deep sea (abyssal plain)
Interpret the energy level of the water which deposited sample S, and offer a justification why you made that choice.
a. Calm water, since it is so coarse-grained.
b. Calm water, since it is red.
c. Calm water, since it is fine-grained and very thinly laminated.
d. High-energy currents, since it is so coarse-grained.
e. High-energy currents, since it is red.
f. High-energy currents, since it is so fine-grained and thinly-laminated.
c. Calm water, since it is fine-grained and very thinly laminated.
Examine the coarse-grained samples T, U, V, and W.
Which of the 4 samples features clasts of vesicular basalt?
Sample U
Overall color of the rock will be dark, typically black or gray.
The surface of the clasts will be rough and pitted due to the presence of vesicles.
The vesicles themselves will appear as small, round to oval holes scattered throughout the rock.
Some vesicles may be filled with secondary minerals (like zeolites) or may be empty.
Examine the coarse-grained samples T, U, V, and W.
Which of the 4 samples features clasts of granite?
Sample V
Examine the coarse-grained samples T, U, V, and W.
Which of the 4 samples features well-rounded clasts of green mudrock?
Sample T
Rounded Clasts: Rounded clasts are rock fragments or pebbles that have been worn smooth and rounded by the action of erosion and transportation. They are commonly found in riverbeds, beaches, and other environments where water or other forces have shaped and polished them over time.
Green Mudrock: Green mudrock, also known as green shale or greenstone, is a type of sedimentary rock composed mainly of fine-grained clay minerals and other mineral particles. It gets its name from the greenish color imparted by the presence of minerals like chlorite or other ferrous iron compounds. Green mudrock is often associated with marine environments and is formed through the gradual accumulation of mud and organic matter over geological time scales.
Examine the coarse-grained samples T, U, V, and W.
Which of the 4 samples is unlithified?
Sample W
“unlithified,” it means the material is in a loose, unconsolidated state, meaning it is not yet a solid rock but rather sediment. This stage precedes the process of lithification, where sediment is transformed into solid rock through compaction and cementation.
Examine the coarse-grained samples T, U, V, and W.
Which of the 4 samples features clasts that are the most angular of the group?
Sample V
Examine sample X.
There is a prominent sedimentary structure to be seen in this sample. Identify this primary sedimentary structure.
a. raindrop impressions
b. graded bed(s)
c. current ripple marks (also called “asymmetrical ripple marks”)
d. cross-bedding
b. graded bed(s)
Interpret sample X.
Based on the sedimentary structure you identified in the previous question, what interpretive statement can you make about the conditions under which this sediment was deposited?
a. It must have been on the land.
b. It must have been exposed to the air.
c. It must have had flowing currents of water.
d. It must have been deposited in a swampy environment with stagnant water.
e. It must have been in a shallow water environment where waves could reach the bottom.
f. It must have been in the deep ocean, deposited by turbidity currents.
f. It must have been in the deep ocean, deposited by turbidity currents.
Examine sample Y.
Sample Y is a sandstone. Note its color.
What does this implies a depositional setting (sedimentary environment) in terms of its oxygen levels?
a. It indicates that the depositional setting was relatively low in free oxygen.
b. It indicates that the depositional setting was relatively high in free oxygen
b. It indicates that the depositional setting was relatively high in free oxygen
Examine sample Z.
There are two prominent sedimentary structures to be seen in these samples. One are the empty cylindrical tubes. These are ancient animal burrows. Identify the other primary sedimentary structure.
a. raindrop impressions
b. graded bed(s)
c. current ripple marks (also called “asymmetrical ripple marks”)
d. cross-bedding
d. cross-bedding
NOT these but good explanation:
Raindrop impressions: Raindrop impressions are typically small depressions left on the surface of sediment or sedimentary rocks by raindrops.
Graded beds: Graded beds refer to sedimentary layers with a gradual change in grain size from coarse at the bottom to fine at the top.
Current ripple marks: Current ripple marks, are sedimentary structures formed by the action of water or wind currents.
Interpret sample Z.
Based on the sedimentary structure you identified in the previous question, what interpretive statement can you make about the conditions under which this sediment was deposited?
a. it must have been on the land.
b. It must have been exposed to the air.
c. It must have had flowing currents of water and these currents switched direction periodically.
d. It must have been deposited in a swampy environment with stagnant water.
d. It must have been in a shallow water environment where waves could reach the bottom.
e. It must have been in the deep ocean, deposited by turbidity currents.
c. It must have had flowing currents of water and these currents switched direction periodically.
Which of the following can contain fossils?
a. sedimentary rocks
b. metamorphic rocks
c. minerals
d. igneous rocks
a. sedimentary rocks
Which of the following can result in lithification of sediments to make sedimentary rock?
a. cooling and crystallization of lava
b. compaction and/or cementation
c. combustion, consumption, or dissolution
d. weathering and erosion
b. compaction and/or cementation
Which environment would be likely to produce a black shale?
a. sand dunes (e.g., Sahara Desert)
b. shallow tropical carbonate bank, far from land (e.g., the Bahamas)
c. swamp (e.g., Great Dismal Swamp, Virginia)
d. forest (e.g., Shenandoah National Park, Virginia)
c. swamp (e.g., Great Dismal Swamp, Virginia)
Which group of three minerals are the most common minerals in sedimentary rocks?
a. quartz, clay, and calcite
b. olivine, pyroxene, and garnet
c. pyrite, galena, and gypsum
d. quartz, fluorite, and chlorite
a. quartz, clay, and calcite
________ describes the range in particle sizes in a detrital sedimentary rock.
a. composition
b. sedimentary structure
c. sorting
d. rounding
c. sorting
Which of the following methods of transportation will result in the poorest sorting?
a. glaciers
b. rivers
c. wind
d. beach waves
a. glaciers
Examine this image of a sedimentary rock. Which of the following choices is the best name for this specimen of rock?
a. limestone
b. shale
c. sandstone
d. conglomerate
e. breccia
f. rock salt
d. conglomerate
___________ are tiny inorganic particles created when small sediments or shell fragments are rolled by waves in warm water supersaturated with calcium carbonate. Layers of CaCO3 accumulate around this “nucleus” to make a concentrically-zoned structure, like a hailstone or a jawbreaker.
a. Bryozoans
b. Ooids
c. Stromatolites
d. Cross-beds
b. Ooids
The primary basis for classifying detrital rocks is ________ whereas the primary basis for classifying chemical rocks is ________.
a. Particle shape; trace elements
b. Crystalline structure; Sorting
c. Particle size; mineral composition
d. Sorting; density
c. Particle size; mineral composition
Examine the photograph below, and identify the sedimentary structure it depicts. The scale bar at left is in centimeters.
a. ripple mark
b. fossil
c. cross-bedding
d. ooids
e. mud cracks
f. laminations
g. graded bed
g. graded bed
Due to the particle size being larger, stream gravel needs a swift current to be transported whereas sand needs a current with less energy.
a. True
b. False
a. True
Dark, poorly sorted sandstones with angular clasts are called arkose and are often associated with turbidity currents.
a. True
b. False
b. False
Contact metamorphism occurs ___________.
a. in regions of mountain-building
b. adjacent to intrusions of magma or lava
c. where meteorites impact
d. in areas exposed to hot water
d. in areas where sediments are layered deeply, building up to tremendous thicknesses
b. adjacent to intrusions of magma or lava
Which texture forms in areas of mountain-building?
a. Foliated
b. Nonfoliated
c. Clastic
d. Chemical
e. Biochemical
a. Foliated
Explanation:
Mountain building processes involve intense compression and heat, which causes the minerals in rocks to align and form layers, creating a foliated texture.
Why other options are incorrect:
Nonfoliated:
Nonfoliated textures develop in metamorphic rocks that have not undergone significant shearing or compression, and are typically formed under conditions of high heat but low pressure. These rocks are not as prevalent in areas of mountain building.
Clastic:
Clastic textures describe the composition of sedimentary rocks, which are formed from accumulated sediment particles. This texture is not related to the metamorphic processes that occur during mountain building.
Chemical:
Chemical textures are the result of recrystallization of minerals due to chemical reactions. While some chemical metamorphism can occur during mountain building, it is not the primary process responsible for the formation of foliated textures.
Biochemical:
Biochemical textures are related to the formation of rocks from organic materials. This is not relevant to the textures formed in areas of mountain building.
Serpentinite is a metamorphic rock that results from the __________.
a. contact metamorphism of oceanic crust
b. regional metamorphism of granite
c. burial metamorphism of shale
d. contact metamorphism of carbonate rock such as limestone
e. hydrothermal metamorphism of shale
f. regional metamorphism of carbonate rock such as limestone
g. burial metamorphism of granite
h. hydrothermal metamorphism of oceanic crust
h. hydrothermal metamorphism of oceanic crust
Confining pressure dominates in areas where ____________ is happening.
a. subduction
b. burial metamorphism
c. mountain-building
d. faulting
e. differential stress
b. burial metamorphism
What is the difference between marble and quartzite?
a. Quartzite is composed of the mineral calcite; marble is composed of the mineral quartz.
b. Quartzite is composed of the mineral quartz; marble is composed of the mineral calcite.
c. Quartzite is composed of quartz sandstone; marble is composed of limestone.
d. Quartzite is composed of sandstone; marble is composed of granite.
e. Quartzite is composed of limestone; marble is composed of sandstone.
f. Quartzite is composed of shale; marble is composed of granite.
b. Quartzite is composed of the mineral quartz; marble is composed of the mineral calcite.
Mylonite shows evidence of _________.
a. partial melting
b. a calcite-rich protolith
c. shock metamorphism
d. flow in some minerals, and grain size reduction in others
e. Shallow depths and low temperatures
d. flow in some minerals, and grain size reduction in others
Mylonite is a metamorphic rock formed due to intense shearing, which causes the deformation of the original rock. This deformation leads to the “flow” of some minerals within the rock, while simultaneously reducing the grain size of the overall rock matrix.
What type of metamorphism would be most likely occur adjacent to a hot spring?
a. burial metamorphism
b. thermal metamorphism
c. hydrothermal metamorphism
d. contact metamorphism
e. regional metamorphism
f. shock metamorphism
c. hydrothermal metamorphism
Explanation:
Hydrothermal metamorphism refers to the alteration of rocks due to the interaction with hot, chemically active fluids, which is precisely what happens around a hot spring where hot water circulates through the surrounding rock.
Metamorphism of a shale at a low metamorphic grade produces which of the following metamorphic rocks?
a. marble
b. greenschist
c. eclogite
d. metaconglomerate
e. phyllite
e. phyllite
Explanation: Phyllite is a foliated metamorphic rock that forms from shale when the clay minerals recrystallize into tiny mica flakes, giving it a silky sheen.
Why other options are incorrect:
Marble:
Marble is formed from the metamorphism of limestone, not shale.
Greenschist:
Greenschist is a low-grade metamorphic rock, but it is typically formed from mafic igneous rocks, not shale.
Eclogite:
Eclogite is a high-grade metamorphic rock formed under very high pressure and temperature conditions. It is not associated with the low-grade metamorphism of shale.
Metaconglomerate:
Metaconglomerate is a metamorphic rock formed from the re-crystallization of clasts within a conglomerate. It is not the result of the metamorphism of shale.
Small glass droplets produced as a result of meteorite impact melting are _____.
a. aureoles
b. plutons
c. tektites
d. porphyroblasts
e. shocked quartz
c. tektites
Explanation: When a meteorite strikes Earth, the intense heat can melt surrounding terrestrial rocks, which then solidify into glass droplets as they cool upon re-entering the atmosphere.
Key points about the other options:
Aureoles: These are zones of metamorphosed rock around a magma intrusion.
Plutons: These are large bodies of igneous rock that form deep within the Earth’s crust.
Porphyroblasts: These are large crystals that form within a rock matrix.
Shocked quartz: This is a type of quartz that has been deformed by high pressure, often due to a meteorite impact.
Which of the following lists puts metamorphic rocks in the order of increasing grain size (and increasing grade of metamorphism)?
a. slate, schist, phyllite
b. phyllite, slate, schist
c. slate, phyllite, schist
d. schist, slate, phyllite
c. slate, phyllite, schist
Explanation: Slate has the finest grain size with the lowest metamorphic grade, followed by phyllite with a slightly larger grain size and higher grade, and finally schist with the coarsest grain size and highest grade among these three rocks.
Key points about the options:
Slate: Very fine-grained, with a layered appearance due to compressed mudstone.
Phyllite: Slightly coarser than slate, with a more wavy texture due to the development of mica minerals.
Schist: Coarsely crystalline rock with visible mica flakes forming distinct bands.
What is the protolith of marble?
a. Granite
b. Quartz sandstone
c. Limestone
d. Slate
e. Blueschist
f. Shocked quartz
c. Limestone
Explanation: A protolith is the original rock from which a metamorphic rock forms. Marble is a metamorphic rock, and limestone is the sedimentary rock that transforms into marble through metamorphism.
What is the protolith of Quarzite?
a. Granite
b. Quartz sandstone
c. Limestone
d. Slate
e. Blueschist
f. Shocked quartz
b. Quartz sandstone
Quartz sandstone is a sedimentary rock, but it metamorphoses into quartzite.
Explanation: A protolith is the original rock from which a metamorphic rock is formed, and in the case of quartzite, the parent rock is sandstone, which is primarily composed of quartz grains. Under high pressure and temperature conditions, the quartz grains in the sandstone recrystallize and become tightly packed together, forming quartzite.
What is the protolith of Slate?
a. Granite
b. Quartz sandstone
c. Limestone
d. Shale
e. Blueschist
f. Shocked quartz
d. Shale
Slate is a metamorphic rock that forms from shale, a type of mudstone.
Explanation: A protolith is the original rock from which a metamorphic rock is derived, and in the case of slate, shale is the parent rock that undergoes low-grade metamorphism to form slate.
What is the protolith of Blueschist?
a. Granite
b. Quartz sandstone
c. Limestone
d. Slate
e. Blueschist
f. Basalt
f. Basalt
Blueschist is a high-grade metamorphic rock that forms under high pressure and relatively low temperatures. It is typically derived from basalt or other mafic rocks, not limestone
An extremely hot metamorphic rock may begin to ___________, producing the rock called _______.
a. cool; blueschist
b. react; marble
c. melt; migmatite
d. break; mylonite
e. flow; slate
c. melt; migmatite
Explanation: When a metamorphic rock is subjected to extreme heat, it can partially melt, forming a mixture of melted rock and solid rock fragments, called migmatite.
Key points about the other options:
Blueschist:
This is a metamorphic rock formed under high pressure and relatively low temperature, not due to extreme heat.
React:
This is not a specific geological term describing the process of an extremely hot metamorphic rock.
Marble:
Marble is a metamorphic rock formed from the recrystallization of calcite or dolomite under high pressure and temperature, but it does not result from melting.
Break/mylonite flow/slate:
These terms describe different geological processes or rock types not related to the melting of an extremely hot metamorphic rock.
Which metamorphic rock is most likely to contain the mineral garnet?
a. Schist
b. Marble
c. Quartzite
d. Slate
e. Serpentinite
f. Fault breccia
a. Schist
Explanation: Schists are often characterized by the presence of larger crystals, called porphyroblasts, which can include garnet.
Why other options are incorrect:
Marble:
Marble is a non-foliated metamorphic rock primarily composed of calcite. It doesn’t typically form under the conditions necessary for garnet formation.
Quartzite:
Quartzite is mainly composed of quartz and forms under high pressure conditions, but not the conditions that favor garnet formation.
Slate:
Slate is a low-grade metamorphic rock formed from shale. It usually doesn’t have the high temperatures and pressures needed for garnet development.
Serpentinite:
Serpentine is formed from the metamorphism of olivine-rich rocks. Garnet is not typically associated with its formation.
Fault breccia:
Fault breccia is a rock formed from broken fragments cemented together by pressure. It’s not a metamorphic rock and doesn’t have the conditions necessary for garnet formation.
What tectonic process is implied by blueschist?
a. Subduction
b. Rifting
c. Strike-slip faulting
d. Earthquakes
e. Partial melting
f. Weathering and erosion
a. Subduction
Explanation: Blueschist is a metamorphic rock that forms under conditions of high pressure and relatively low temperature, which are typical of subduction zones where one tectonic plate dives beneath another.
Why other options are incorrect:
Rifting:
Rifting involves the splitting apart of tectonic plates, which creates conditions of low pressure and high temperatures, not the conditions necessary for blueschist formation.
Strike-slip faulting:
Strike-slip faulting involves plates sliding past each other, causing earthquakes along the fault lines. This type of tectonic activity does not produce the high-pressure environment needed for blueschist formation.
Earthquakes:
Earthquakes are the result of sudden movements along fault lines, not a specific tectonic process that leads to the formation of blueschist.
Partial melting:
Partial melting is a process that occurs when rock melts due to high temperature, usually in the mantle. While this can lead to the formation of certain metamorphic rocks, it is not associated with the high-pressure, low-temperature conditions characteristic of blueschist formation.
Weathering and erosion:
Weathering and erosion are processes that break down rocks at the Earth’s surface, not deep within the Earth where blueschist forms.
The chemical formula Al2SiO5 can form any of these three minerals, given different combinations of temperature and pressure conditions:
a. marble, quartzite, and hornfels
b. quartz, feldspar, and mica
c. hematite, magnetite, and goethite
d. andalusite, kyanite, and sillimanite
e. granite, sandstone, and marble
d. andalusite, kyanite, and sillimanite
Explanation:
The chemical formula Al2SiO5 can represent different minerals depending on the temperature and pressure conditions during its formation. Andalusite, kyanite, and sillimanite are all polymorphs of Al2SiO5, meaning they have the same chemical composition but different crystal structures due to varying environmental conditions.
Metamorphism of a rock can result from __________.
a. increase of pressure
b. increase or temperature
c. exposure to reactive chemical fluids
d. all of the above
d. all of the above
Explanation: Metamorphism is the process by which rocks change form due to changes in their environment, primarily caused by alterations in temperature, pressure, and the presence of chemically active fluids.
Increased pressure:
As rocks are buried deeper into the Earth, they experience increased pressure from the weight of the overlying rock. This pressure can cause the rocks to recrystallize and change their texture.
Increased temperature:
High temperatures can also trigger metamorphism. Heat promotes recrystallization of minerals and can lead to the formation of new minerals that are stable at higher temperatures.
Exposure to reactive
chemical fluids:
Chemically active fluids can facilitate metamorphic reactions by dissolving and transporting minerals within the rock. These fluids can also introduce new elements or compounds, further altering the rock’s composition and mineralogy.
Foliation is a common texture in many metamorphic rocks. What is foliation?
a. the compaction and resultant decrease in volume of a rock during metamorphism
b. the transformation of unstable minerals into stable forms during metamorphism
c. the preferred alignment of elongate or platy minerals, or the banding of mafic and felsic minerals
d. the removal of all fine-grained minerals from a rock during intense metamorphism
c. the preferred alignment of elongate or platy minerals, or the banding of mafic and felsic minerals
Explanation:
Key points about foliation:
Alignment of minerals: When a rock undergoes metamorphism under pressure, the platy minerals like mica tend to align themselves parallel to the direction of pressure, creating a layered appearance.
Banding: This can also result in the formation of bands with alternating layers of different mineral compositions, like mafic and felsic minerals.
Types of foliated rocks: Slate, schist, and gneiss are examples of foliated metamorphic rocks where the layering is evident.
A rock with a gneissic texture is characterized by __________.
a. large, recrystallized mineral grains
b. the alignment of clays in a low-grade metamorphic rock
c. a homogenous collection of similar sized and similar composition minerals in a metamorphic rock
d. a banding of light and dark minerals in a metamorphic rock
d. a banding of light and dark minerals in a metamorphic rock
Explanation: The term “gneissic texture” refers to the distinct banding pattern in gneiss, where lighter colored minerals like feldspar and quartz alternate with darker minerals like mica or feldspar, created under high heat and pressure during metamorphism.
One type of non-foliated metamorphic rock is __________.
a. quartzite
b. slate
c. schist
d. phyllite
a. quartzite
Explanation: Quartzite is a non-foliated metamorphic rock formed from sandstone when quartz grains recrystallize under heat and pressure, resulting in a dense, hard rock without a layered appearance.
Another type of non-foliated metamorphic rock is marble.
Key points about the other options that are incorrect:
Slate:
A foliated metamorphic rock with a fine, layered texture formed from shale.
Schist:
A foliated metamorphic rock with a more pronounced layering than slate, often composed of mica minerals.
Phyllite:
A foliated metamorphic rock with a slightly wavy texture, transitioning between shale and schist.
Why is marble considered non-foliated metamorphic rock?
Non-foliated rocks:
These metamorphic rocks lack a layered or banded appearance because their mineral grains don’t align in a particular direction during metamorphism.
Marble:
Marble is a metamorphic rock formed from the metamorphism of limestone or dolostone. It’s characterized by its lack of foliation, meaning the mineral grains (primarily calcite) are not arranged in parallel bands.
Other examples:
Other common examples of non-foliated metamorphic rocks include quartzite and hornfels.
A metamorphic rock whose parent rock was a limestone is referred to as __________.
a. quartzite
b. marble
c. slate
d. migmatite
b. marble
Explanation: Marble is formed when limestone undergoes heat and pressure, causing the calcite crystals within it to recrystallize, resulting in a denser, more crystalline rock.
Key points about the other options:
Quartzite:
This metamorphic rock is formed from sandstone, which is primarily composed of quartz.
Slate:
This is a low-grade metamorphic rock that usually originates from shale or mudstone.
Migmatite:
This is a high-grade metamorphic rock that shows evidence of partial melting and is often composed of a mixture of igneous and metamorphic material.
