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Geology > Final Exam > Flashcards

Final Exam Flashcards

1
Q

Steps of the scientific method

A

Observations –> Questions –> Hypothesis –> Testing/Experimentation (refine/reject/start over) –> Develop Theory

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2
Q

What is our crust made out of?

A

silicate (Si & O) rich and Fe-poor

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3
Q

What is our mantle made out of?

A

silicate (Si & O) with more Fe

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4
Q

What is our core made out of?

A

Fe and Ni, no silicate

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5
Q

What is the lithosphere like / its phase of matter?

A

solid, cold, brittle outer shell of planet

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6
Q

What is the asthenosphere like / its phase of matter?

A

solid, warm, ductile (plastic) layer beneath lithosphere

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7
Q

What is the mesosphere like / its phase of matter?

A

solid, warm layer beneath asthenosphere

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8
Q

What is the outer core like / its phase of matter?

A

liquid, hot Fe, Ni layer beneath mesosphere

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9
Q

What is the inner core like / its phase of matter?

A

solid, hot Fe, Ni layer beneath outer core

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10
Q

How does the Earth form from the remnants of a dead star?

A

Star dies/explodes –> nebula –> cooling –> accretion –> planet

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11
Q

What is the early 20th century evidence that the continents moved?

A
  • Apparent fit of continents across the Atlantic (Pangea supercontinent)
  • Same land fossils on different continents
  • Evidence of glaciers in areas now at equator
  • Same rocks and mountain ranges across oceans
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12
Q

What is the mid-late 20th century evidence of plate tectonics?

A
  • Magnetic stripes in seafloor rocks of alternating polarity on either side of mid-ocean ridge
  • Seafloor mapping (sonar/bathymetry) revealing ridges and trenches
  • Age stripes in seafloor rocks…rocks get older moving away from mid-ocean ridges
  • GPS data
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13
Q

Characteristics of the oceanic crust:

A

dense and thin crust with more Fe and less Si and O (rock = basalt)

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14
Q

Characteristics of the continental crust:

A

less dense and thick crust with less Fe and more Si and O (rock = granite)

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15
Q

How does oceanic crust form?

A

by volcanism at divergent plate boundaries (decompression melting)

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16
Q

How does continental crust form?

A

by volcanism at convergent plate boundaries (hydrous melting at subduction zones)

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17
Q

Characteristics of convergent boundaries (ocean-ocean, continent-ocean, continent-continent convergent)

A
  • Earthquakes on one side of plate boundary and increasing in depth with increasing distance from the oceanic trench
  • Volcanoes at subduction zones, not at continent-continent convergent
  • Volcanoes at subduction zones are in same area as deepest quakes (far from trench)
  • Mountains at all convergent boundaries due to compressional stress
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18
Q

Characteristics of divergent boundaries. (oceanic-oceanic and continent-continent divergent)

A
  • Shallow earthquakes right on the plate boundary (at the ridge/rift valley)
  • Volcanoes occur right on the boundary (right on the ridge/rift valley)
  • Valleys formed where plates spread apart (extension)
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19
Q

Characteristics of transform boundaries

A
  • Lots of shallow earthquakes
  • No volcanoes
  • No mountains or rift valleys here
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20
Q

What is a mineral?

A

Natural, inorganic, solid, ordered structure (lattice), specific chemical composition

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21
Q

What are the characteristics that we use to identify a mineral and how do we analyze them/test them?

A
  • Cleavage – ability to break along planes of weakness
  • Hardness – resistance to scratching
  • Luster – how a mineral reflects light (metallic/non-metallic)
  • Streak – color of mineral when powdered
  • Crystal habit – shape mineral makes when it grows
  • Color – the color the mineral reflects
  • Special properties – reaction to acid, magnetism, heft
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22
Q

What is the key chemistry of the different mineral groups?

A
  • Silicates (SiO2) – most common mineral group in crust – makes up igneous rocks. Also, clastic sediments, and metamorphic rocks that derive originally from igneous rocks – quartz, feldspar, micas
  • Carbonates (CO3) – very common in water – calcite mineral in limestone
  • Oxides (O2) – result of “rusting” oxidation of metals – hematite mineral
  • Halides (Cl) – Salt!
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23
Q

In what tectonic environments do igneous rocks form (how do you make magma)?

A
  • Decompression melting at divergent boundaries (Mid-Ocean Ridge/Iceland)
  • Hydrous melting at subduction zones (continental-oceanic or oceanic-oceanic convergent) (Andes Mountains, Cascade Mountains)
  • Mantle plumes melting the lithosphere (Hawaii, Yellowstone)
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24
Q

Texture of igneous rocks and what does it indicate?

A
  • Coarse grained = intrusive/plutonic = slow cooling
  • Fine grained = extrusive/volcanic = fast cooling
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25
Q

Mineralogy/composition of igneous rocks and how do we determine it?

A
  • Mafic = >70% dark minerals.
    Dark minerals are rich in Fe but low in Si and O (olivine, pyroxene, plagioclase feldspar)
  • Intermediate = 50-70% dark minerals
  • Felsic = < 30% dark minerals.
    Felsic minerals are poor in Fe but rich in Si and O (quartz, K-feldspar, micas)
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26
Q

What types of igneous rocks are associated with oceanic crust?

A

Mafic = basalt/gabbro = oceanic crust = form at divergent plate boundaries

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27
Q

What types of igneous rocks are associated with continental crust?

A

Felsic = rhyolite/granite = continental crust = form at subduction zones

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28
Q

What does it mean to be an effusive volcano, what are they made of, and where do they occur?

A
  • Non-explosive, erupts lava flows (aa and pahoehoe) mostly
  • Comprised of mafic igneous rocks (basalt)
  • Mafic magma has low viscosity (is runny) and doesn’t explode because gas can escape
  • Effusive volcano types = shield volcanoes (Hawaii) and rift volcanoes (Iceland)
  • Effusive volcanoes form on oceanic crust like Hawaii (mantle plume) and Iceland (divergent boundary)
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29
Q

What does it mean to be an explosive volcano, what are they made of, and where do they occur?

A
  • Explosive, can erupt pyroclasts (ash fall and flows) and lava flows
  • Comprised of intermediate (andesite) and felsic (rhyolite) igneous rocks
  • Intermediate and felsic magma have a high viscosity (are sticky) and explode due to trapped gas
  • Explosive volcano types = stratovolcanoes (Mt. St. Helens) and calderas (Yellowstone)
  • Explosive volcanoes form on continental crust like Yellowstone (mantle plume) or Mt. St. Helens (subduction zone)
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30
Q

Characteristics of sedimentary rocks?

A

Layered in outcrop (originally horizontal)
Clastic = comprised of pieces of other rocks deposited, buried, compacted, and cemented into a rock
- Shale, Sandstone, Conglomerate
Chemical = chemicals precipitated or evaporated out of water
- Limestone, Rock Salt

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31
Q

How do we classify clastic sedimentary rocks?

A

Grain size
- Fine (clay, silt), medium (sand), coarse (gravels)
Sorting
- Well sorted = clasts that are all same size
- Poorly sorted = clasts of different sizes
Roundness
- Rounded = clasts rounded by water transport
- Angular = clasts deposited without water transport

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32
Q

Sedimentary characteristics in high energy clastic environments…

A
  • landslides, fast rivers
  • Grain size = coarse (sand to gravels)
  • Sorting = poor
  • Roundness = angular to sub-rounded
  • Rock Type = Breccia and Conglomerate
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33
Q

Sedimentary characteristics in medium energy clastic environments…

A
  • slower rivers, beaches
  • Grain size = medium (sand)
  • Sorting = well
  • Roundness = well rounded
  • Rock Type = Sandstone
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34
Q

Sedimentary characteristics in low energy clastic environments…

A
  • deeper marine settings
  • Grain size = fine (silt and clay)
  • Sorting = very well
  • Roundness = very well rounded
  • Rock Type = Shale
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35
Q

Sedimentary characteristics chemical environments…

A
  • marine, lake, groundwater settings
  • Limestone = calcite precipitation in warm, clear marine water with life.
  • Rock salt = halite evaporation in warm, salty water.
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36
Q

How do metamorphic rocks form?

A
  • Heat and/or pressure with no melting
  • Contact metamorphism = just heat = rocks in contact with lava/magma
  • Regional metamorphism = heat and pressure = metamorphism from compression and shear at convergent plate boundaries (accretionary wedge) or buried to deep depths
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37
Q

Unique textures associated with metamorphic rocks?

A

In order of increasing heat and pressure (low grade to high grade) changes to a parent rock include…
- Close pore spaces/increase density (low grade)
- Existing minerals recrystallize (get larger) (low to medium grade)
- Minerals become stretched and compressed (foliation) (medium to high grade)
- Minerals separate by type (banding) (high grade) (if there are multiple types)

38
Q

Common parent rocks and their metamorphic equivalents - Note, the parent rocks here are all common rocks in the ocean that get sandwiched between plates at an accretionary wedge

A
  • Shale –> Slate = low grade (foliated clay minerals)
  • Shale –> Mica Schist = medium grade (foliated mica minerals)
  • Shale –> Gneiss = high grade (banded feldspars, micas, quartz)
  • Sandstone –> Quartzite = any grade (quartz just getting bigger)
  • Limestone –> Marble = any grade (calcite just getting bigger)
39
Q

Structural rules for sedimentary rocks:

A
  • Law of Original Horizontality = layers original form horizontally
  • Law of Superposition = layers on bottom are older than layers on top
40
Q

Kinds of deformation of sedimentary rocks:

A
  • Compressive stress = pushing stuff together = convergent plate boundaries - Ductile/plastic behavior = folded rocks (anticlines/synclines) & Brittle behavior = reverse faults
  • Extensional stress = pulling stuff apart = divergent plate boundaries - Brittle behavior = normal faults
  • Shear stress = stuff tearing or sliding against each other = transform/strike slip plate boundaries - Brittle behavior = transform/strike slip faults
41
Q

Anticlines

A
  • Folds with an A-like frame in cross-section view
  • Layers tilt/dip away from axis of fold
  • When eroded, oldest rock is exposed in the middle in map view - striped pattern gets younger moving away from central axis
42
Q

Synclines

A
  • Folds that look like a U or V in cross-section view
  • Layers tilt/dip towards the axis of the fold
  • When eroded, youngest rock is exposed in the middle in map view - striped pattern gets older moving away from central axis
43
Q

Normal fault

A

extensional stress = divergent plate boundaries = rift valleys
(hanging wall falls relative to footwall)

44
Q

Reverse fault

A

compressional stress = convergent plate boundaries = orogenic belts (mountain ranges)
(hanging wall rises relative to footwall)

45
Q

Strike slip fault

A

shear stress = transform/strike slip plate boundaries
(No hanging or foot
Right-lateral movement means other side of fault from you has moved to your right
Left-lateral movement means other side of fault from you has moved to your left)

46
Q

Law of original horizontality

A
  • Sedimentary rocks are originally deposited in horizontal layers
  • Deformation events (folding/tilting) occur after sediments form
47
Q

Law of superposition

A

Oldest rocks are on bottom and youngest on top

48
Q

Principle of cross-cutting relations

A

Features like faults and intrusions (dykes, sills, batholiths) that cross-cut other rocks must be younger than the rocks they cross-cut

49
Q

Principle of inclusions

A

Rocks that are entirely contained in another rock must be older than the rock that contains them

50
Q

Unconformities

A
  • Represent missing time in the rock record
  • Typically form because the land was uplifted and eroded at some point…this removes rock
51
Q

Principle of Faunal Succession

A
  • Organisms evolve and go extinct in a predictable pattern across Earth
  • Fossil time ranges do not change (dinos always come before humans)
52
Q

Correlation (in age dating techniques)

A
  • We match up rocks and fossils across the planet to build the geologic timeline.
  • Index fossils are best for correlation (Index fossils = organisms that live for short period of time across entire planet)
  • Ash layers are good for correlation too (Ash layers spread across entire planet and can be dated using radioactive decay technique)
53
Q

Technique of absolute age dating – radiometric age dating

A
  • Minerals in rocks capture radioactive material when the minerals first form in magma/lava
  • Radioactive parent isotope decays/changes to a stable daughter product (Example: radioactive Carbon-14 decays to stable Nitrogen-14)
  • Decay process happens at steady rate (Half life = time it takes for half of radioactive parent material to change to a stable daughter)
54
Q

The half life of Carbon-14 is 5730 years. Pretend you begin with 500 g of carbon. How much Carbon-14 is left after 17,190 years?

A
  • 17,190 represents 3 half-lives (5730 x 3)
  • Time = 0 = 500 g of Carbon-14
  • Time = 1 half life = 250 g of Carbon -14
  • Time = 2 half lives = 125 g of Carbon -14
  • Time = 3 half lives = 62.5 g of Carbon -14
  • After 3 half lives = 62.5 g Carbon-14 and 437.5 g Nitrogen-14
  • 62.5 g / 437.5 g = 0.1429 = 1:7 ratio of parent to daughter
55
Q

What kind of rocks are good for radiometric age dating?

A

Igneous rocks = best rocks - Minerals trap radioactive material during cooling of magma/lava. Then, radioactive clock starts ticking
- Extrusive igneous rocks the absolute best…especially ash, because they cool quickly and often cover large areas of Earth (good for correlating rocks with absolute age constraints)

56
Q

What kind of rocks are bad for radiometric age dating?

A

Sedimentary rocks = bad rocks for dating
- Clastic rocks in particular are made of millions of pieces of other igneous, sed, and meta rocks – you would get millions of different formation ages

Metamorphic rocks = bad rocks
- Metamorphism (head and pressure) can release (cause it to escape) the radioactive material from the mineral, resetting decay clock

57
Q

How do rivers initially form?

A
  • Runoff from rain erodes a channel
  • Channels funnel flow then widen, deepen, and lengthen (Lengthening occurs by headward erosion)
  • Channels/valleys capture more flow along their walls, creating tributaries
58
Q

What is the most common drainage pattern?

A

Dendritic drainage = tree branch pattern of small tributaries that contribute water to larger channels

59
Q

Watersheds

A

the areas that capture rainfall and funnel flow to the main trunk river

60
Q

Drainage divides

A

topographic ridges that separate different watersheds

61
Q

How do rivers change as you move from the highlands to the coastal plains?

A
  • Slope/gradient (change in elevation with distance) of the landscape decreases
  • Rivers change from straight –> braided –> meandering
  • Rivers become larger (more tributaries entering main river)
  • Rivers gain more water (higher discharge)
  • Rivers gain more sediment (until its dumped in ocean at a delta)
  • Sediment in rivers becomes smaller (gravel –> sand –> silt –> clay)
62
Q

What controls formation of straight rivers?

A
  • Steep slopes drive vertical incision
  • River becomes locked into rock and can’t migrate side to side
  • Also, lots of downhill momentum (like a bike on a steep hill)
  • No floodplain
63
Q

What controls formation of a braided river?

A
  • Lower slope
  • Lots of sediment (too much!)
  • Rapid deposition (due to slope break – mountains to plains)
  • Sediment gets in the way, channel switches (avulsion) location frequently
64
Q

What controls formation of meanders?

A
  • Lowest slope
  • Fine-grained sediment
  • Cohesive, vegetated channel banks made of sticky clay and silt resist, but don’t prevent lateral erosion
  • Meanders form due to continuous cut bank erosion and point bar deposition
  • Wide floodplain
65
Q

How does water get into the ground?

A

Rocks must be porous! – have holes
Porous rocks must also be permeable! – holes must be connected!

66
Q

What are the most porous rocks?

A

Sedimentary rocks

  • Porosity improves if = clasts are well sorted
  • Porosity improves if = clasts are rounded
  • Sandstone = most porous (well sorted and rounded)
  • Shale = also very porous (well sorted and rounded)
  • Limestone can be porous due to acid weathering (karst)
  • Some igneous rocks (vesicular) are also porous
67
Q

What are the most permeable rocks?

A

Specific sedimentary rocks

  • Sandstone is permeable (larger connected holes!)
  • Limestone can be permeable (holes or big caves connected to each other)
  • Shale is impermeable (too many tiny holes!)

Igneous rocks are never permeable unless fractured/cracked

68
Q

Where is groundwater stored in the ground?

A
  • Water table = shallow groundwater source (rain infiltrates into ground). Also known as the unconfined aquifer or the saturated zone
  • Aquifers = porous and permeable rocks that hold water
  • Aquitards = impermeable rocks that don’t transmit water (can’t get through) *Confined aquifers have aquitards above and below
69
Q

How does groundwater move underground?

A
  • Water in water table flows downhill (follows gravity)
  • Level/elevation of water table mimics overlying topography
  • Water in deeper aquifers can move uphill against gravity if water is under pressure
70
Q

How do we get water from the ground and how do we measure it?

A
  • We pump water from the ground at wells
  • Each well records elevation of water table (or aquifer)
  • We generate contour lines to record water table elevation
  • We use contour lines to determine flow direction and speed (gradient) of flow
  • Water flows downhill in direction perpendicular to contours
  • We use contour lines to determine where groundwater pollution is going and where it is coming from
71
Q

Consequences of over-use? (groundwater)

A
  • Too much pumping = cone of depression in water table
  • Too much pumping can lead to subsidence of ground (collapse)
  • Too much pumping near the ocean can bring salt water into our water table
72
Q

How does a delta form and why are they important?

A
  • Deltas form where rivers enter bodies of water and flow decelerates
  • Rapid deposition leads to channel switching/branching (avulsion)
  • The distributary pattern leads to fan-shaped feature
  • Rivers/deltas deliver sand to the coastline…source of beach sand
73
Q

How do waves form and how do they change when approaching the shoreline?

A
  • Waves are made from friction between the wind and water
  • Waves grow in size with stronger winds, longer travel distance (fetch), and longer wind event
  • Waves oscillate up and down in the open sea (oscillating wave)
  • Waves slow down, grow in size, and spill over (break) in shallow water near the coast as wave base interacts with seabed (translational wave)
  • Wave breaking and surf moves sand onto beach (swash)
  • Gravity can pull sand back down off the beach (backwash)
  • Waves hit beach at an angle creating longshore drift/longshore current
  • Longshore drift transports sand along the coastline (Responsible for spit formation)
74
Q

Not every beach is made of the same stuff? Why?

A

Composition of beach sand reflects composition of rocks on land and duration/distance of transport from the land

75
Q

Continental crust beaches =

A

granite rocks = felsic minerals = (quartz, feldspar, mica minerals)

  • Quartz is strongest and most chemically resistant of continental crust minerals
  • Most beaches that are far away from the original source rock (the mountains) are made of quartz and nothing else because of long term chemical breakdown of everything but quartz, feldspar and mica turn to clay and get carried out to sea
  • For beaches that exist very close to their granite source, you sometimes get feldspar and mica on the beach (not enough time/distance to change feldspar and mica to clay)
76
Q

Oceanic crust beaches =

A

basaltic rocks = mafic minerals (olivine, pyroxene, plagioclase)

Beaches on oceanic crust can be dark to black (even green!) in color due to their mafic source, these are more rare… more beaches on continental crust because most land is made of continental crust

77
Q

Beaches near coral reefs =

A

= limestone rocks = calcite minerals/shell fragments/reef fragments

These white sand beaches come from waves destroying reef structures and transporting reef/shell fragments

78
Q

How do the tides work and how do they influence beach morphology?

A
  • Tides form by the gravitational attraction between the Earth and Moon
  • The difference in high tide level and low tide level = tidal range
  • At any given moment on Earth, there are two high tide bulges and two low tide regions
  • Due to Earth’s 24 hour rotation…each location experiences two high tides and two low tides per day (high changes to low in 6 hours)
  • Tides expose different parts of the coast to waves (creating tall wave cut notches or piles of sediment high on beach)
  • Tides create a low energy current that can only move mud (silt and clay)
  • Tidal energy is lower than wave energy
  • In places of weak waves, you might notice tidal energy and see silt and clay deposition only (no sand), waves leave sand – tides leave mud
  • Tidal flats or mud flats are coastal regions dominated by tidal energy (weak waves)
79
Q

How does sea level influence a coastline?

A

There are there types of coastlines categorized by sea level change:

  • Submergent coast = rising sea level relative to land
  • Emergent coast = falling sea level relative to land
  • Static coast = no change in relative sea level
80
Q

Submergent coastline features

A
  • East coast of the US (south of Massachusetts) is a submerging coastline
  • Sea level is rising everywhere due to melting of glaciers (warming of climate)
  • Estuaries are common = river valleys flooded with seawater
  • Barrier islands are common = beaches partially submerged by seawater
  • Lagoons are common = swamped region behind barrier island
81
Q

Passive margin submergent coastlines

A
  • Passive continental margins are the edges of continents that are far away from a plate boundary
  • Coastlines on passive margins are flat (very flat) with broad beaches
  • Because they are so flat, they are susceptible today to sea level rise and are most often submergent
82
Q

Active margin emergent coastlines

A
  • Active continental margins are the edges of continents that are close to a plate boundary
  • Many coastlines on active margins are very steep with small beaches and tall bedrock cliffs
  • These sea cliffs are produced at these locations by tectonic uplift of the land relative to sea level
83
Q

Passive margin emergent coastlines

A
  • Some passive margins are uplifting today!
  • The northern hemisphere had large, thick glaciers during ice age
  • These locations are rebounding upwards (isostasy!) due to glacial melting
  • This uplift creates sea cliffs in places like Quebec, Norway, England, France, etc, which are all on the passive margin Atlantic coast
84
Q

What are the common continental glacial features (from the Pleistocene ice age) in NY?

A
  • moraines
  • glacial striations
  • glacial erratics
  • drumlins
  • eskers
  • kettles
  • u shaped glacial troughs
85
Q

Moraines

A

pile or ridge of unsorted materials (till) in the front of (or sometimes edges of) glaciers

End moraine = moraine at the front/end of a glacier

Till = unsorted sediment associated with glacial transport – contains clay, silt, sand, gravel, and boulders!

86
Q

Glacial striations

A

scratches on bedrock created by abrasion between rocks in ice and the ground

87
Q

Glacial erratics

A

large boulders of a unique origin (from Canada usually) left behind by the glacier

88
Q

Drumlins

A

streamlined/tear-drop shaped hills comprised of glacial till

These features are piles of till that have been dragged along the base of the glacier in the direction of glacial flow
Drumlins are ideal paleo-flow indicators because:
- In map view, many are tear drop shaped. Point of tear drop points in direction of flow
- In map view or cross-sectional view, the steep side of a drumlin is the “upstream side” and the gentle side is the “downstream side”

89
Q

Eskers

A

snake like hills formed by stream deposition within a glacial tunnel

  • When glaciers melt, they make rivers beneath them
  • Rivers flow in tunnels that leave sediment behind (usually better sorted than tills)
  • When the glacier melts, the snake like meandering pile of river sand and gravel is left behind
90
Q

Kettles

A

small, almost circular depressions that are often filled with rainwater

  • Kettles are made when the glacier leaves an iceberg behind
  • The iceberg then gets partially buried by sediments (usually glacial stream sediments)
  • Once the iceberg melts, it leaves a hole in the ground where the iceberg once was. This then fills with water
91
Q

U-shaped glacial troughs

A

Finger Lakes

  • Glaciers carved broad, U-shaped valleys where narrow V-shaped river valleys once existed, today, many of those U-shaped valleys in NY are filled with lakes - Unfortunately, our valley next to campus no longer has a lake, but there is a U-shaped valley beneath all the river sediment from the Genesee, we live next to a glacial trough
92
Q

What is glacial ice and what causes a glacier to form?

A
  • Glaciers form when accumulation of snow exceeds loss/melting of snow (ablation)
  • If snow (90% air by volume) can accumulate, it can compress (metamorphose) into denser, more crystalline, glacial ice (20% air by volume)
  • Glaciers advance (get bigger) when accumulation > ablation
  • Glaciers retreat (get smaller ) when accumulation < ablation
  • Glaciers flow downhill on a thin film of water
    Note: glaciers flow even when they are advancing or retreating
    Glacial flow is not the same thing as glacial advance

Geology (4 decks)

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