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Our Dynamic Earth > 11/10 TEST > Flashcards

11/10 TEST Flashcards

1
Q

what are igneous processes?

A

processes that involve…The melting of rock and production of magma; The evolution of magma/lava chemistry; The cooling of magma/lava; The eruption and intrusions of molten rock; The migration of magma and how lava flows/erupts

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2
Q

What do Igneous processes result in?

A

Magma and lava (melts); Igneous rock: after cooling; landforms/geological features

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3
Q

Where can you find Igneous rocks?

A

In the crust (intrusive settings) cool at depth; lose heat slowly, large crystals, mostly felsic (high silica content); At earth’s surface (extrusive settings) melts cool at or near the surface; cool rapidly; small crystals; mostly mafic

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4
Q

what is and in lava and magma? what are the main elements of molten rock? what is a volatile and the two most abundant in magma/lava?

A

Magma: molten material in the ground; lava: molten material when it is on the Earths surface. Elements: Mostly silicon and oxygen; Other elements: Fe, Mg, Al, K, Ca, Na; Volatiles: Substances that exist as gasses at the earths surface; Mostly H2O, CO2, CO, H2S

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5
Q

what is polymerization?

A

linkage of atoms/molecules (silica tetrahedra) into larger molecules

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6
Q

what is melt (magma/lava) composition? magma/lava (and igneous rocks) are categorized by the % of silica

A

Felsic magma 66-76% — slow moving lava
Intermediate magma: 52-66%
Mafic magma: 45-52% silica
Ultramafic magma: 38-45% silica — doesn’t exist because earth’s surface isn’t as hot

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7
Q

What is partial melting?

A

Process by which minerals within a rock melt in order according to melting temperature; In nature, it is rare for the entire rock to melt; The vast majority of magmas on earth are produced from the asthenosphere from ultramafic of partial melting; The resulting magma will be more silica rich than its source

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8
Q

What is partial melting in rock?

A

Asthenosphere rock: ultramafic (olivine, pyroxene, garnet)
Each mineral has a different melting point. The mineral with the lowest melting point will melt first : pyroxene, garnet; Other minerals will follow, some minerals will never melt because their melting conditions are never met; Ultramafic rock – partial melting = mafic magma

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9
Q

what are the 3 processes that trigger partial melting of rock?

A

The addition of volatiles – at convergent boundaries; Decompression melting – divergent boundaries, continental rifts, mantle plumes, sea floor spreading; Heat-induced melting – multiple locations – island arcs and subduction zones
AV & DM occur at specific tectonic conditions; HIM can occur wherever magma currently exists

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10
Q

Addition of volatiles (convergent boundaries)

A

Convergent boundaries - Voltalies (H2O, CO2) derived from the subducting plate mix with the asthenosphere; Bonds break, melting begins; Decreases the melting temperature of the asthenosphere (allows periodite to partially melt at a lower temperature); Subducting plate DOES NOT melt;;; volatiles are dissolved into the asthenosphere and decrease its melting point. the mantles melting point has been lowered by the addition of volatiles.

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11
Q

Heat - Induced Melting ( multiple locations)

A

As magma rises through the crust, heat from the melt transfers to the surrounding crust (country rock); The heat triggers partial melting of the crust; This can generate silica rich melts (felsic). process of transforming solid mantle into liquid magma by simply applying heat,

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12
Q

what are the 3 processes that change composition?

A

Fractional crystallization – process by which minerals crystallize from a melt as the melt cools, minerals crystallize in a specific order depending upon melt chemistry and melt temperature. As minerals crystallize the chemistry of the magma evolves; Assimilation – evolving magma has a different chemical composition, process of blocks (source rock) of rock fall into magma and dissolve.; Magma mixing – volumes of magma rise through crust; 2 magmas rise at different times and they can mix and melt into the other magma body

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13
Q

what is Fractional Crystallization?

A

Process by which minerals crystallize from a melt as the melt cools. Minerals crystallize in a specific order depending on melt chemistry and melt temperature. As minerals crystallize, the chemistry of the magma evolves; Increases magma silica content making it more felsic. Olivine is a mafic mineral with a high melting point. When ultramafic magma cools, the olivine crystallizes first and settles to the bottom of the magma chamber, the remaining melt becomes more silica rich and felsic.

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14
Q

what is the Bowens Reaction Series? What are the two series?

A

Bowen ran experiments with melts; Melts crystallize at high temperature, when magma/lava reaches the freezing point of minerals; Minerals crystallize in a specific order- called bowen’s reaction series
Minerals solidify in a specific sequence; Continuous - plagioclase changed form Ca rich to Na rich; Discontinuous - minerals that solidify in a narrow T range - Both series will occur at the same time

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15
Q

What is assimilation?

A

Evolving magma has a different chemical composition; Process of blocks of rock fall into magma and dissolve; Crust is very silica rich; Pieces of country rock with a different composition are added to the magma. These solid pieces may melt which changes the composition of the original magma; Process by which rising magma incorporates country rock and composition changes.

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16
Q

what is magma mixing?

A

Volumes of magma rises through crust, 2 magma rise at different times and they can mix and melt into the other magma body

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17
Q

what are igneous intrusions? and country rock?

A

Geological features that were caused the “intrusion” of magma into the crust; Magma get stuck and cools/crystallize beneath earths surface; Country rock – underlying lithified rocks that make up the geologic record in an area, only the deeper, crystalline (non layered) rocks

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18
Q

what are tabular intrusions?

A

long, but thin shaped intrusion. Ex. table top; Dikes and sills; Dikes: tabular intrusions that cut across preexisting layering ( bedding )
Sills: tabular intrusions that occur when magma is injected parallel to preexisting layering - Effects landscape : can uplift rock from resistant ledges

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19
Q

what are massive intrusions?

A

intrusions that form bulbous or balloon type shapes; Plutons and batholiths; Plutons: balloon shaped masses of igneous rock; Crystallized magma chamber; large volume; Batholiths : many connected plutons - Yosemite – mostly felsic. Associated with subduction zones.

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20
Q

what is a volcano?

A

A geographic feature in which lava erupts at earth’s surface; Mountain, depression, caldera, fissure/crack

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21
Q

what are the 2 factors that deal with eruption style?

A

Factor 1: viscosity
Viscosity: a material’s resistance to flow; Higher viscosity = higher explosivity
2 things can influence a melts viscosity - Composition: lavas with a lower silica content are less viscous; Temperature: hotter lavas are less viscous
Factor 2: volatiles
Volatile content has the greatest influence on eruption style (more than viscosity); Typically, the more voltalies, the more explosive the eruption; Escaping voltalies form bubbles which burst

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22
Q

What is a effusive style volcano?

A

Hawaiian and icelandic styles: fountains of low viscosity lava eruption from a central crater or fissure. Viscosity: low; volatile: low; explosivity: very low; basaltic lava

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23
Q

what is a moderately explosive eruption style?

A

Strombolian style- “burps” of magma. Basaltic pyroclastic eruption; viscosity:low; volatile:high; explosivity: low - moderate;; Pyroclastic flows: plinian style hazard
Pyroclastic flows: superheated dense ash clouds that move

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24
Q

what are eruptive materials?

A

Eruptions produce..Lava (they flow in different ways); Tephra: volcanic debris of various sizes; Gasses; These materials will be produced in different quantities depending on eruption style

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25
Q

what are the basaltic lava flow types?

A

Pahoehoe - basalt with a glassy, ropy surface texture; A’a’ - basalt that solidifies with a jagged, sharp, angular, glassy, surface texture — very very slow; Pillow basalt: round blobs of basalt cooled in the presence of water; common at divergent plate boundaries

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26
Q

what is pyroclastic debris?

A

Tephra: deposits of pyroclastic debris of any size. Types: ash, lapilli, bombs and blocks; volcanic ash is finer farther away from eruption

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27
Q

what is volcanic gas?

A

Around 1 to 9% of magma (by weight) may be gas. Ex water, carbon dioxide, sulfur dioxide; Rhyolitic magmas have highest gas content; mid ocean ridges basalts has the lowest gas content

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28
Q

what is the volcanic explosivity index?

A

Measure of the explosivity of a volcanic eruption based upon how much tephra was released; more tephra = higher explosivity

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29
Q

What are fissure volcanoes?

A

magma/lava may erupt along a linear crack, a fissure; Hawaiian style eruption with basaltic lava; divergent boundaries

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30
Q

What is a crater/vent volcano?

A

Lava is erupted at a central vent. Mountains forms as erupted lava piles up around the vent; The volcano itself is composed of:
Layers of lava flows; Alternating lava flows and tephra (even pyroclastic flow materials)

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31
Q

What are shield volcanoes?

A

Large volcanoes with broad, “gentle”, flants result from the eruption of low viscosity lava, common at oceanic hotspots. Mafic magma chambers. Kilauea Hawaii.

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32
Q

what are stratovolcano/composite volcano?

A

Volcanoes with very steep sides, high elevation, produced by alternating effusive and pyroclastic eruptions. Felsic to intermediate magma chambers but can even produce mafic lavas. Explosive eruptions.

33
Q

what are cinder/scoria cone volcano?

A

Short, stalky volcano with a deep crater and steep sides, produced from strombolian eruptions. Mafic lavas with a high content of volatiles.

34
Q

what is a caldera?

A

Volcanic crater produced during highly explosive eruptions and portions of the underlying magma chamber empty. a depression where a volcano erupts and collapses

35
Q

What are the igneous processes at subduction zones?

A

Addition of volatiles; Partial melting of the asthenosphere; Magma rises due to buoyancy; Heat transfer and assimilation

36
Q

what are the mid ocean ridge processes?

A

Decompression melting: decrease in pressure, asthenosphere rises; Partial melting; Sea floor spreading

37
Q

what is weathering?

A

the physical and chemical breakdown of rock at or near the Earth’s surface. In response to a rocks changing environment, first step in forming a sedimentary rock

38
Q

what is the defintion of erosion?

A

the process of removing weathered material from its source rock. Liquid water is the main agent of erosion.

39
Q

explain the physical weathering process

A

The physical break down of rock into smaller pieces; Frost Wedging- Ice wedges into rock a crack opens then water seeps through, water expands into rock causes rock to split apart; Root Wedging - Inherent weakness within the rock; plants can grow into tehse holes, roots absorb water, roots cause rock to split apart

40
Q

definition of chemical weathering process?

A

Chemical reactions breakdown rock and minerals, involves the alternation of mineral crystalline structures, produces material stable at Earths surface

41
Q

what are the 4 processes of chemical weathering?

A

Oxidation - Iron rich minerals lose an electron to oxygen, producing iron oxides; Oxidation of sulfide minerals = acid mine drainage: oxidation of sulfide minerals, results in iron oxide deposits (orange color) and acidic waters; Dissolution - Chemical reaction between acid and minerals (generally calcite), minerals ionize in acids; Causes caves/caverns;; Hydrolysis - Hydrogen ion (dissolved in water) enters the crystalline structure of minerals, displaces other cations and new mineral forms; Hydration - Water combines with a mineral, Water disrupts the crystalline structure of anhydrite. Atoms rebond into a new crystalline structure, incorporating water

42
Q

what is spheroidal weathering?

A

When rocks weather, corners and edges weather the fastest as a result edges and corners are “rounded” generating a sphere

43
Q

Why does magma rise? Discuss vesiculation and buoyancy.

A

Buoyancy – most magmas are 10% less dense than equivalent solid rock; Vesiculation – dissolved volatiles may expand and form bubbles as pressure decreases. This will lower density and increase buoyancy further.

44
Q

Be able to describe Decompression Melting. How does this process work? Where, on Earth, does it occur?

A

Caused by lowering pressure; Magma is created at mid-ocean ridges (divergent boundaries) by decompression melting. Convection currents cause mantle material to rise, the pressure decreases which causes the melting point to drop. As this magma continues to rise it cools and crystallizes to form new lithospheric crust.

45
Q

Why does the oceanic crust have a mafic composition?

A

Lava and intrusive rocks combine to form the crust. The molten material that solidifies to form a new oceanic crust is mafic.

46
Q

When a rock partially melts, a magma forms. How does the composition of the magma differ from the source rock?

A

Partial melting produces a magma a step lower on the Bowen diagram than the rock from which it melts. Partially melting an ultramafic rock produces a magma with a mafic composition.

47
Q

Describe aphanitic, porphyritic, and phaneritic textures. Are they intrusive or extrusive textures? How does a porphyritic texture form?

A

Phaneritic: coarse, crystalline texture, cooled beneath earth’s surface, intrusive; Aphanitic: fine grained, too fine to distinguish between, extrusive; Porphyritic: aphanitic texture larger coarse crystals floating in an aphanitic background, both.

48
Q

what are vesicles and a vesicular texture?

A

Vesicles – holes; Vesicular texture: gas bubbles become trapped in the solidifying lava

49
Q

Know the composition and cooling location (intrusive/extrusive) of the following rocks: periodic, gabbro, diorite, granite, basalt, andesite, and rhyolite

A

Peridotite – ultramafic phaneritic coarse grained, gabbro – coarse grain mafic, diorite – coarse intermediate intrusive, granite – coarse grain felsic phaneritic intrusive, basalt – fine-grained mafic extrusive, andesite – fine crystalline intermediate extrusive, rhyolite – ultramafic aphanitic fine grained

50
Q

What is a pyroclastic flow and how does it form? What style of eruption and type of volcano is associated with pyroclastic flows?

A

Superheated, dense ash clouds that move – Plinian style hazard. Composite volcanoes. Pyroclastic = rocks that are formed from eruptive volcanoes; a collapsed part of the eruption column that travels down at very hot temperatures and very fast speeds made of dense ash clouds, lava blocks and pumice and hot gasses.

51
Q

Describe volcanism (volcanic shapes, lava compositions, eruptions styles( at the following tectonic regimes: Divergent, Continental rifting, subducting zones, hotspots

A

Divergent Plate Boundaries – mid-ocean ridge volcanism: melting generates a mafic, poor volatile magma/lava; results in effusive fissure eruptions and pillow basalts; majority of volcanism occurs here.
Cont. Rifting – many volcano and lava types reflecting: asthenosphere and continental crust- results in small shield volcanoes, cinder cones, stratovolcanoes. Subduction zones – stratovolcanoes and Plinian eruptions style reflect : high silica content melts and high volatiles content. Hotspots – main source of intraplate volcanism. Silica poor basalt magma. Less explosive.

52
Q

What types of minerals are susceptible to dissolution?

A

Chemical reaction between acid and minerals (acidic) minerals ionizes in acids.

53
Q

How do the two types of weathering work together to break down rock?

A

Physical weathering produces more surface area, allowing more of the rock exposed to the elements; chemical weathering produces products than can be easily transported. With more surface area exposed, chemical reactions can work faster.

54
Q

What factors influence weathering rates? Be able to discuss/explain how these factors influence weathering rates.

A

Mineral composition – not all minerals or rocks weather at the same time and rate; Abundance of joints – continental rift zones create joints; water gets into joints/fractures and can facilitate more physical weathering; more cracks and joints results in higher weathering rates. Climate – influences: abundance of water; how fast rocks weather; the dominant weathering processes

55
Q

Which types of minerals are more stable at the earth’s surface. What types are unstable?

A

Olivine (unstable) hates being at the earth’s surface, so it weathers fast. Quartz is incredibly resistant to weathering (stable) most common mineral in sedimentary rocks.

56
Q

What is differential weathering? Why does it occur?

A

Different rocks in the outcrop weather at different rates – dependent on composition of rock; creates cliffs and slopes; stair step features. Stair step topography: Switches from material being resistance to weathering and material that isn’t resistant to weathering.

57
Q

What are soils? What is regolith?

A

Soil: material derived from the weathering of rock, composed of mineral, organic matter, water and air – it is a type of regolith. Regolith: unconsolidated material that overlies solid bedrock, ex. Sand on a beach

58
Q

What are sedimentary rocks and what are the three different categories of sedimentary rocks?

A

form at or near the earth’s surface in one of several ways produce on of 3 different types (classes)
Clastic: deposition, accumulation, and lithification of rock fragments – derived from weathering processes
Chemical: precipitation of minerals from a solution or by an organism
Organic: accumulation and alteration of plant matter before decay

59
Q

Describe the different types of clastic sedimentary rocks, what are their grain sizes, and do they suggest to geologists?

A

Breccia: the gravel is angular – indicates small degree of weathering and transportation; Conglomerate: the gravel is rounded.
Breccia & Conglomerate depositional environements – mountain ranges, mountain streams, some landslide deposits; Sandstone: made of sand-sized particles, found in beach and desert settings, indicates higher degrees of weathering and transportation; Arkose Sandstones: sand and gravel with abundant feldspar; indicates: minor degree of weathering and transportation, depositional environment: alluvial fan and stream; Shale: composed of silt, clay, and mud that breaks into platy sheets – indicates: stagnant water; depositional environment: lake, swamps, deep ocean

60
Q

How does a geologist describe a clastic texture? What is grain size? Sorting? Angularity? Sphericity? Clast composition? How are these characteristics affected by transportation

A

Sorting: the degree to which the clasts are the same size, transportation affects sorting by being well sorted when it is farther away from source because they have had time to sort out. Angularity: smooth edges is rounded as transportation increases the rock becomes more rounded.

61
Q

What is subduction and at what type of boundary does it occur?

A

The process by which oceanic lithosphere sinks into the mantle; subduction recycles oceanic lithosphere – convergent boundaries.

62
Q

What is sea-floor spreading and at what type of boundary does it occur?

A

Process by which new oceanic crust is created at mid ocean ridges, creating and widening ocean basins – divergent boundaries.

63
Q

What are the requires for a substance to be considered a mineral?

A
  • Naturally occurring
  • Inorganic
  • Solid
  • Well defined chemistry
  • Crystalline structure
64
Q

What is a crystalline structure?

A

How the atoms are organized will depend upon atomic size.

65
Q

What is crystalline texture? How does intrusive crystalline textures differ from extrusive crystalline textures…and why?

A

Extrusive rocks are often vesicular filled with holes from escaping gas bubbles, fine-grained; Intrusive rocks have coarse grains; Crystalline textures: when it is composed entirely of mineral crystals, they interlock together making it incredibly strong.

66
Q

What is diagenesis and lithification? Be able to explain the lithification process.

A

Lithification involves: Compaction = burial adds pressure to sediment, Cementation: minerals grow in pore spaces. Lithification is how a rock is formed.
Diagenesis occurs when the sediments are altered. Burial= higher pressures and temperatures

67
Q

How are clastic sed rocks formed?

A

Weathering: generation and removal of clasts/ chemicals from parent rock, Erosion/transportation: dispersal by wind, water, ice, and or gravity, Deposition: settling out of the transporting fluid, Burial,Lithification and diagenesis: transformation into solid rock and alteration of sediment

68
Q

In general, what are the four main components of an average soil? What are their proportions?

A

25% Air, 25% water, 45% minerals, and 5% organic matter

69
Q

What is a soil horizon?

A

A type of non-eroded sediment mixed with organic matter, used by plants. Soil horizons make up the soil profile. The top horizon is the O horizon, A horizon, B horizon, C horizon, and R horizon.

70
Q

Why do magmas rise?

A

magma rises because it is less dense, squeezed upward, uses preexisting cracks, as it rises melts and incorporates some of the rock it encounters. movement is controlled by its viscosity - depends on : composition, volatile content, and temperature.

71
Q

what is chert?

A

A rock made of microcrystalline quarts, secreted by organisms or through precipitation from a solution found in deep ocean waters

72
Q

How do evaporate rocks form?

A

evaporated from sea or lake water

73
Q

What is coal and in what type of environment does it form?

A

Altered remains of fossil vegetation; accumulates in a swampy environment, requires deposition in the absence of oxygen

74
Q

What are sedimentary structures?

A

Features in a clastic sedimentary rock that form while the sediment is still loose. Preserved when the sediment lithifies.

75
Q

What are ripple marks and how do they form?

A

Cm scale ridges and troughs; develop perpendicular to flow of wind, water. Dunes : large scale ripple marks ; Asymmetrical : develop from flow in one direction (a current). Symmetrical: develop in the presence of an oscillating current (Waves) form back and forth motion

76
Q

What is cross bedding and how does it relate to ripple marks?

A

Created by ripple and dune migration, sediment moves up the gentle side of a ripple or dune then slips down the steep face

77
Q

What are mud cracks and how do they form?

A

Polygonal desiccation features in wet mud; surficial only indicates alternating wet and dry terrestrial conditions

78
Q

What is graded bedding and how does it form?

A

Fining upward sequence of grains, thorough going not just surficial, indicates underwater landslide (turbidity current), suggests steep unstable submarine slope

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