FINAL Questions Flashcards
What is the difference between rocks and surficial materials?
a
What are the weathering processes that physically break a preexisting rock apart to form “sediment?”
a
What are the weathering processes that chemically break down preexisting rocks?
a
How does carbonic acid form?
a
What is the chemical reaction that describes the dissolution of the mineral calcite?
a
The orientation of cave passageways in limestone and other soluble rocks is controlled by what structures?
joints
Why does dissolution occur along these structures?
a
What is meant by the term “Karst?”
cave and hydrology below ground water system
Why is there little surface drainage (e.g. rivers) in areas underlain by soluble rock?
water flows underground
How do sinkholes form? How might you recognize a sinkhole?
underground is eroded, sinkholes will appear as rounded depressions in the ground
Knowing that stream frequently flow into sinkholes and disappear into the cave systems underground, what are some of the consequences of dumping trash in sinkholes?
groundwater pollution
Areas where the plants, surface streams, and lakes are most affected by acid rain generally lack what what types of minerals in the surficial materials or underlying bedrock?
calcite
What happens to feldspar minerals when they are weathered by hydrolysis?
dissolves into clay and soluble quartz
What happens to the strength of rocks if they are susceptible to weathering by hydrolysis?
weakened
Why do rocks weather more quickly at corners (where 3 joints intersect) than along their faces?
more exposure
How does spheroidal weathering occur?
corners eroded away
Why are the granites in Vermont almost unweathered while the granites in some parts of Colorado are deeply weathered?
colorodo older.
What happens to an iron-magnesium-bearing mineral like pyroxene when it weathers by oxidation?
rusts
Rust is actually one of several minerals with different structural forms, but the same chemical formula. What mineral class does rust belong to?
iron-oxide-hydroxide
What happens when a sulfide mineral like pyrite weathers by oxidation?
rust
Explain the different ways that mining processes can greatly accelerate the rate at which pyrite oxidation takes place.
When coal is burned the pyrite in it oxidizes to produce sulfur dioxide which dissolves in water in the atmosphere to produce sulfuric acid, one of the sources of human-produced acid rain. mine tunnels containing pyrite expose large volumes of pyrite to oxygen and water.
What are the climatic variables that control the rate of chemical weathering?
temperature, wetness, acidic
Learn to recognize the differences between the chemical formulas for dissolution, hydrolysis, and oxidation.
a
What are some of the byproducts of chemical weathering processes, i.e. what kinds of materials are left after minerals in rocks undergo chemical weathering?
1) Are any of these useful to plants? 2) Where does the dissolved silica end up? Hint: Think about the process by which loose sediment turns into sedimentary rock. 3) Why are the soils that develop on ultramafic rocks toxic to many plants?
What are some common physical weathering processes?
frost wedging, sheeting, thermal expansion
Explain how frost wedging works.
water in cracks freezes
In what type of climate is frost wedging most effective as a physical weathering process?
New England
What processes can move weathered materials (surficial materials) once they form?
water erosion
Make a list of the different size classes of sediment (e.g. sand) based on size.
Boulder Cobble Pebble Sand Silt Clay Mud
Make a list of the different types of clastic sedimentary rock based on the size of the sediment.
Boulder Conglomerate Cobble Conglomerate Pebble Conglomerate Sandstone Siltstone Shale Mudstone
How do surficial materials (sediment) turn into sedimentary rocks?
Lithification: cemented together (by Quartz and Calcite)
Do surficial materials (sediments) need to be deeply buried to turn into sedimentary rock?
No
Compare the energy of the water currents capable of moving coarse sand versus the energy of water currents capable of moving silt sized sediment.
Higher energy to move larger particles
What are some of the environments that conglomerates are deposited in?
Streams
What are some of the environments that siltstones and shales are deposited in?
deep sea basins, low energy
What are some of the environments that sandstones are deposited in?
beach environments
What are the biochemical sedimentary rocks composed of?
Calcite from shells and skeletons. Form Limestone
What are the chemical sedimentary rocks composed of ?
Formed from concentrated inorganic ions (Slat, Halite, Gypsum Dolostone)
How does dolostone form?
Mg2+ cations (dissolved in groundwater) substitute for one of the Ca2+ cations in the original calcite, turning it into dolomite.This process is one type of RECRYSTALLIZATION.
What are some of the common evaporite minerals?
Halite (NaCl), Gypsum (CaSO4*2H2O), Anhydrite (CASO4)
Where would you go in the world today to find environments where evaporite minerals are being deposited?
Closed Basins, Salt Lake Utah
What are organic sedimentary rocks composed of?
Composed of partially decayed plant and animal remains—hydrocarbon compounds.
What types of environments do organic sedimentary rocks form in?
Peat Bogs, Tar pits
What is the difference between peat vs lignite coal vs bituminous coal?
he peat transforms first to lignite and then to bituminous (soft) coal. If the temperatures rise further (200–300°C), the bituminous coal transforms to anthracite (hard) coal.
Why are coal mines more dangerous than other types of mines?
Can catch on fire! methane, carbon monoxide, sedimentary rocks are prone to failure
What are some of the changes that allow you to see bedding in sedimentary rocks?
changes in color, grain size, mineral
What are some of the changes in the environment that sediments are deposited in that might produce changes from one layer of sediment to another?
fluctuations in water current, sea level changes,
Draw a profile of an asymmetric ripple mark and an arrow showing the direction(s) water currents were moving when this ripple mark formed.
Draw a profile of an symmetric ripple mark and an arrow showing the direction(s) water currents were moving when this ripple mark formed.
Draw a profile an an asymmetric ripple mark showing the orientation of the cross-bedding within that ripple. Include an arrow showing the direction water currents were moving at the time the ripple mark formed.
a
Why do mud cracks form in sediment containing clay minerals and not sand?
clay minerals expand when wet and shrink when dry, much like an accordion.The water is taken in between the clay mineral layers.
Some beds within the Monkton formation, the rock you looked at on your first field trip to Redstone Quarry, contain mud cracks. What is this telling you about the environment that the Monkton formation was deposited in?
alarge scale drainage basins
What types of plants or animals are most likely preserved as fossils?
hard structured calcite rich
What types of plants or animals are least likely preserved as fossils?
soft body parts without skeletons
What are the different ways that fossils can form and be preserved in rocks?
carbon film, impression, petrification, recystalization
What is the difference between a “real” fossil and a “trace” fossil?
real are created from the living thing (a foot), trace was left by the fossil (foot prints)
What kinds of information can be gleaned from trace fossils?
the type of living organism, size, wieght, locomotion, feeding habits
A bed of sedimentary rock consisting entirely of broken pieces of fossils is telling you what about the environment those fossils were deposited in?
death assemblage
A bed of sedimentary rock consisting of beautifully preserved fossils consisting of delicate and intricate shells is telling you what about the environment those fossils were deposited in?
calm environment where they had formed.
What is chert and how does it form?
Chert (also known as “flint”) is very fine-grained and breaks along sharp concoidal fractures, similar to the way that glass breaks. Chert has been used to make tools (e.g. arrowheads, spear points) by people for a long time.
Made from the shells of organisms
Sediments that are well sorted by grain size have most likely been been transported by wind or water for a relatively short/long period of time?
long time
What happens to the shape of sediment as it gets transported for progressively longer distances or is in eroded by moving water or wind for progressively longer periods of time?
more rounded
What happens to the composition (the proportion of different minerals in the sediment) of sediment as it gets transported for progressively longer distances or is in eroded by moving water or wind for progressively longer periods of time?
more and more sorted
What span of time is represented by the Geologic Time Scale?
all of history
What is the definition of an “Unconformity?
is an old erosion surface and represents a period of time when no sediments accumulated.
What is an “Orogeny?”
a
The oldest rocks near Burlington were formed during the Grenville Orogeny. What do we know about this orogeny?
.When Laurentia rifted apart from the rest of Rodinia a new ocean formed, the Iapetus Ocean Grenville Orogeny was the rifting of Rodinia
What types of rocks were formed ~30 km below the surface during the Grenville orogeny?
a
What is the relationship between the Grenville Orogeny and the supercontinent of Rodinia?
a
When did the first abundant, easily visible, hard-shelled fossils first evolve?
Archaen
What happened to the Grenville Mountains during the 500 million years after they formed?
a
How much of the overlying mountain belt has eroded since the Grenville Mountains formed to expose the rocks we see at Earth’s surface today in the Adirondack mountains (the mountains across the lake from Burlington)?
a
The first sedimentary rocks deposited in the Champlain Valley were deposited in what kind of depositional environment? What was the plate tectonic environment these rocks were deposited in?
Ocean
The Cheshire Formation largely consists of sandstone. What type of depositional environment existed when this rock formed? What was the plate tectonic environment these rocks were deposited in?
beach
You saw the Dunham dolostone at Lone Rock Point. What changed in the depositional environment between the time when the Cheshire formation was deposited and the time when the Dunham dolostone was deposited?
a
Where could you go in the world today to be in an environment similar to that in which the Dunham dolostone was deposited?
death assemblage
What is happening to relative sea level when a transgression occurs?
sea level either rises of lowers
Give an example of a sequence of sedimentary rocks that might be deposited during a transgression.
a
What is happening to relative sea level when a regression occurs?
a
Give an example of a sequence of sedimentary rocks that might be deposited during a regression.
a
At the time that the Monkton Formation and Danby formation were deposited, was relative sea level in what is now the Champlain Valley relatively high or low? What is the evidence for this?
a
What was the plate tectonic setting of the Taconic Orogeny?
the collision of the volcanic arc and Laurentia produced the Taconic Orogeny (~470–445 Ma).This is what metamorphosed and deformed the rocks in the Green Mountains (what you will see on your last field trip) and caused the thrust faulting and folding you saw at Lessor’s Quarry and will see at Lone Rock Point
What was the plate tectonic setting of the Acadian Orogeny?
The collision of Avalon with North America produced the Acadian Orogeny.
What occurred during the Alleghenian Orogeny?
Alleghenian Orogeny resulted from the collision of Africa with North America.This is the final event that produced the supercontinent of Pangaea
What are the three processes that can occur when rocks are deformed?
Change in location, orientation, shape
Give some examples of how you might know that a rock has been deformed?
a
What is the definition of “stress?”
Pressure = stress = force/area
What is the difference between lithostatic stress and a directed stress?
Lithostatic stress is the stress imparted to rocks that are buried by overlying rocks.
• Similar to being in a pool, rocks buried underground are subjected to stresses that are almost equal in all directions.
Directed - is stress from one direction
What is the difference between a normal stress and a shear stress?
normal stress is all parallel.
What are the conditions that promote materials to deform in a brittle manner?
a
What are the conditions that promote materials to deform in a ductile manner?
a
What is the difference between a joint and a fault?
a
What is a joint set?
a
How can joints influence the topography of a landscape as rocks weather and erode?
a
How do the arches in Arches National Park form?
a
What is the difference between a hanging wall and a foot wall? Can you draw a sketch that illustrates the difference?
a
For dip-slip faults, what is the difference between a normal fault and a reverse fault?
What types of faults would you expect to find in areas undergoing rifting?
a
What types of faults would you expect to find in convergent plate tectonic settings?
a
What occurs to the hanging wall as it moves down along a curved normal fault surface?
a
Is the Wasatch Fault an active fault or one that was only active 100’s of millions of years ago?
active
What are the some of the observations that allow you identify a surface as a fault? You’ve seen some of these on your field trips to Lessor’s Quarry and Lone Rock Point.
a
What happens to the thickness and length of Earth’s crust when normal faults occur?
a
What happens to the thickness and length of Earth’s crust when thrust faults occur?
a
How does the movement along dip-slip faults differ from the movement that occurs along strike-slip faults?
a
What type of plate boundary typically occurs where strike-slip faults are common?
transform boundaries
Folds usually occur when rocks are in what type of plate tectonic boundary?
a
Draw a sketch showing both anticlines and synclines and label these. On this same sketch show where the fold axes are as well as the axial planes of the folds.
a
What are the different processes that can fold rocks?
a
What fold mechanism produced the folds you saw in the rocks at Lessor’s Quarry?
a
What fold mechanism(s) produced the folds you saw at the outcrop in Jonesville (your last field trip)?
thrust fault
What are the geologic structures that allow rocks to shorten and thicken in mountain belts?
a
What is the range of different rock types that can be metamorphosed?
a
What changes in the environment can cause a rock to metamorphose?
a
Some minerals in metamorphic rocks formed during metamorphism, i.e. they weren’t in the original rock. Why does this occur.
a
What is an “Index Mineral?”
a
What is a foliation?
a
What is true about the mica minerals in a rock that has a good foliation?
a
If a sequence of sandstone and shale is metamophosed, which rock type will develop a better foliation? Why?
a
What are the different processes by which foliations can form in rocks?
a
What is the difference between a slate, a phyllite, and a schist?
a
What are some of the common uses of slate?
a
Where is slate found in Vermont?
a
What defines (what allows you to see) the foliation in gneisses?
a
If you were in an area where all the rocks were gneisses, what pressure temperature environment existed when these rocks were metamorphosed?
a
If you were in an area where all the rocks were gneisses, what pressure-temperature environment existed when these rocks were metamorphosed?
a
What is a “migmatite?”
a
When rocks are heated close to their melting points, which minerals are the first to melt?
a
Where do hornfels form?
a
Do hornfels form adjacent to dikes? Why or why not?
a
The minerals in rocks that don’t develop good foliations share some common attributes. What are these?
a
What is marble commonly used for?
a
What is a lime kiln and what is it used for?
a
What is meant by the term “metamorphic grade?’
a
What types of metamorphic rocks typically are found in areas metamorphosed to a low metamorphic grade?
a
What types of metamorphic rocks typically are found in areas metamorphosed at a high metamorphic grade?
a
Where does contact metamorphism usually occur?
a
Where would you typically go to find regionally metamorphosed rocks?
a
