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historical geology > 1st exam > Flashcards

1st exam Flashcards

1
Q

How is Historical Geology studied?

A

With the Scientific Method!

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2
Q

The scientific method is used to…

A
  • Propose
  • Test
  • Provide evidence FOR or AGAINST a given HYPOTHESIS.
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3
Q

What is the Scientific Method?

A

an educated, untested explanation

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4
Q

What are the steps for the scientific method?

A
  • make observations or identify problems
  • make hypotheses to explain observations
  • gather evidence to test hypotheses
  • reject hypotheses (ideally all but one)

Remaining hypothesis is the most probable!

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5
Q

What are plate tectonics?

A

Thin plates that cover Earth’s surface

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6
Q

What marks the positions of plate boundaries?

A

Earthquakes!

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7
Q

How fast do plates move (relative to each other)?

A

a few cm/yr (average)

-> about as fast as nails grow

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8
Q

What are plates composed of?

A

AKA: Lithosphere, are composed of crust + upper mantle.

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9
Q

What are the two kinds of lithosphere (plates)?

A
  • Oceanic

- Continental

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10
Q

Plate motion caused by CONVENTION in the mantle is:

A

density-driven cyclical motion of materials, caused by heat. Ex: When you boil water!

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11
Q

Plates are separated by Plate Boundaries, what are the 3 major types?

A

-Divergent (heading away : )
-Convergent (coming together: –>
<– )

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12
Q

There are two kinds of Divergent plate boundaries… what are they?

A
  • mid ocean ridge

- continental rift

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13
Q

There are three kinds of Convergent plate boundaries… what are they?

A
  • Oceanic-oceanic
  • Oceanic-continental
  • Continental-continenal
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14
Q

What is subduction?

A

when one plate dives under another (less dense goes over, more dense goes under)

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15
Q

Where does a volcanic island arc form?

A

forms on overriding plate

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16
Q

What is a trench?

A

A deep V-shaped intersection of 2 plates

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17
Q

Where does a back-arc basin form?

A

Forms behind islandic arc

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18
Q

Oceanic-oceanic plate boundaries (convergent) feautures……?

A
  • Subduction
  • Volcanic islandic arc
  • Trench
  • Black-arc basin
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19
Q

What do Oceanic-Continental convergent Plate Boundaries feature?

A 
-Subduction 
    =>volcanoes
-Crumpled continent
    =>tall mountains
-Trench
-This is how ocean basins get smaller or close!
-Also affected by accretion.
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20
Q

What is accretion?

A

-Scraped &/or collided materials piled up on continents edge. (One way that continents get bigger!)

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21
Q

What do Continental-Continental convergent P.B’s feature?

A 
-NO subduction, 
  => HUGE interior mountain range
      -Modern ex. Himalayas
-Few volcanoes
-This is another way that continents get bigger, and ocean basins close!
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22
Q

What type of plate boundaries has plates that slide past each other?

A

Transform

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23
Q

What do transform plate boundaries feature?

A

-offset rivers, roads, etc
-no net gain/loss of crust
-no mountains
-no volcanoes
(modern ex. San Andreas Fault)

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24
Q

Which plate boundary connects _____ and convergent P.B’s?

A

Tranform! (connects divergent and convergent p.b’s!)

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25
Q

Who was Alfred Wegener?

A

A German meterologist (1912) who proposed the existence of a “supercontinent” (Pangaea) and continental drift!
(basically the man given credit for the discovery of Plate Tectonics)

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26
Q

What was Wegener’s evidence?

A
  • Coastlines match
  • Glaciation patterns
  • Distribution of ancient equatorial climate belts
  • fossil distribution
  • matching rocks, oceans apart.
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27
Q

What is paleomagnetism?

A
  • Earth like large magnet that points N & S and gives us magnetic poles.
  • When lava cools and solidifies, magnetic minerals align with N & S poles.
  • Magnetic signatures are permanent and record movement of tectonic plates over time.
  • Earth’s magnetic field “reverses” every 250k(avg). Where north becomes south & vice versa.
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28
Q

How are magnetic reversals recorded in some rocks?

A

Some rocks are magnetic and when they are formed the crystals align with the magnetic north.

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29
Q

how are magnetic reversals recorded in oceanic lithosphere important?

A
  • polarity mirrored image on either side of mor.

- can tell you how fast the mor is forming new rocks. also how old rocks are and how long each magnetic reversal lasted.

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30
Q

How does plate tectonics affect the distribution of life on earth?

A
  1. ) geographic barriers.

2. )climatic barriers.

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31
Q

What are geographic barriers?

A

continents break apart and create new habitats. Increases diversity of species. Barriers can form or disappear.

32
Q

what are examples of geographic barriers?

A

1.)Pangaea break-up, isthmus of panama.

33
Q

what are climate barriers?

A

Locations of mountains, valleys, oceans, etc. control local climate and therefore distribution of critters.

34
Q

what is an example of a climate barrier?

A

atacama desert in s. america. the driest place on earth because the mountais and coastal winds prevent rain.

35
Q

what is a mineral?

A

it is naturally occurring, solid, has a lattice.

36
Q

what is a lattice?

A

repeating 3d arrangement of atoms/molecules.

37
Q

what are the mineral classes?

A
  1. )silicates:most diverse and common group. all contain silicone and oxigen. ex: zircon, quartz, opal.
  2. )carbonates:all contain carbon and oxygen. ex:calcite
  3. )halides:salts that contain chlorine, fluorine, or iodine. ex:table salt(halite), fluorite.
38
Q

What are rocks …?

A

accumulations of 1 or more minerals

39
Q

what are the three main types of rocks?

A
  • igneous
  • sedimentary
  • metamorphic
40
Q

igneous rocks are cooled and crystallized from what?

A

-melted rock.

41
Q

Is lava above or below ground?

A

Above! Magma is below ground! Both are associated with volcanoes!

42
Q

What controls crystal size in igneous rocks?

A

-The rate of cooling controls the crystal size and tells you where it cooled.

43
Q

Do fine grained igneous rocks have small or large crystals?

A

-Small crystals

44
Q

If crystals are small in fine-grained igneous rocks, then that means the rate of cooling was….?

A

-slow

45
Q

Fine-grained igneous rocks with small crystals cooled down _____ ground.

A

-Above! Most likely erupted out of a volcano.

46
Q

What size of crystals do coarse-grained igneous rocks have?

A

-Large

47
Q

If crystals are large in coarse-grained igneous rocks, then that mean the rate of cooling of the rock was….?

A

-slow

48
Q

Coarse-grained igneous rocks with large crystals cooled down ______ ground.

A

-below! Most likely was part of what used to be part of a magma chamber.

49
Q

Do glassy igneous rocks have crystals, if so, what size?

A

No crystals!

50
Q

For an igneous rock to be glassy with no crystals, then the rate of cooling must have been…?

A

-Fast! And cooled above ground. Most likely erupted out of a volcano.

51
Q

What are some examples of igneous rocks?

A
  • Peridotite (forms deep in Earth’s mantle)
  • Basalt (is underlying rock in ocean basins)
  • Granite (makes bulk of continent)
52
Q

What are sedimentary rocks?

A

-rocks formed from sediments.

53
Q

What are sediments?

A

-bits and pieces of other rocks and/or organic materials.

54
Q

What are some examples of what sedimentary rocks could be made up of?

A
  • Mud
  • sand
  • gravel
  • leaves
  • etc
55
Q

Where do sedimentary rocks come from?

A
  • weathering (chemical and physical breakdown by wind, water.)
  • transportation (movement of seds by wind, water)
  • deposition (being deposited on beaches, rivers, floodplains, ocean, etc.)
56
Q

What are sedimentary rocks used for?

A
  • To deconstruct Earth’s history!!!
  • they indicate past environment of deposition.
  • almost all fossils are found in sed rocks!
57
Q

What are metamorphic rocks?

A
  • Rocks changed under high temperatures and pressure.
  • primarily due to burial
  • leads to changes in physical or chemical composition.
  • They are cooked but not melted
  • Can happen to any rock type.
58
Q

What are the two types of sedimentary rocks?

A

detrital and chemical

59
Q

what are detrital rocks?

A

from consolidation of fragments (clasts or grains) of pre-existing rocks and/or organic material. mud, sand, gravel, etc…

60
Q

what are chemical rocks?

A

material precipitates from fluids

  1. ) from dissolved minerals in water or
  2. ) through geological processes (critters) for example chalk.
61
Q

what does it mean when a rock has big grain sizes?

A

high energy environment ex. river

62
Q

small grain size?

A

low energy environment ex. lake

63
Q

sedimentary structures:

A

sedimentary rocks commonly occur in layers. strata (beds) and have bedding planes.

64
Q

strata beds=

A

layers like pages in a book. pgs can vary in thickness.

65
Q

bedding planes=

A

horizontal surfaces between strata.

66
Q

uncomformity =

A

time gap

67
Q

how does seasonal variation affect sedimentary structures?

A

abrubt changes in the strata can mean abrupt environmental changes. gradual change can mean gradual environmental change. ex. seasonal variation big grain=> small grain.

68
Q

cross bedding

A

internal multi order layering
ex. lg scale: wind deposition like sand dunes.
small scale:water deposition like rivers, streams.

69
Q

saltation

A

Abrupt evolutionary change; sudden large-scale mutation.

The movement of hard particles over an uneven surface in a turbulent flow of air or water.

70
Q

ripple marks

A

undulations on bedding planes. can be caused by movement of water or wind. back and forth (symmetrical)=open ocean unidirectional (asymmetrical)=river

71
Q

bioturbation

A

the displacement and mixing of sediment particles…ex. barrows, trackways. destroys other sedimentary structures.

72
Q

depositional environments

A

continental, transitional, marine.

73
Q

continental depositional environments

A

FLUVIAL(river):*braided streams(high elevation)
-gravel
-cross-bedding sands
*meandering streams(low elevation)
-muds
-sands
DESERTS: *dunes- large cross-bedding
*alluvial fans- fan shaped at base of cliffs
- layered gravels, sands
GLACIAL: *moraines- material bulldozed by glacier. (different particle sizes)
*varves-fine laminations from seasonal lake sedimentation. can have dropped stones in it. think of glaciers as a solid flowing river.

74
Q

transitional depositional environments

A

DELTAS:triangle shaped deposits where river mouth meets ocean.
-layered sands, mud

75
Q

marine depositional environments

A

SHALLOW:continental shelf, slope & rise

turbudites can occur here.

76
Q

turbudites=

A 
underwater landslides (alluvial fan underwater)
muds, fossils, bioturbation on continental shelf.
77
Q

What are the types of fossilization? Explain.

A
  • Permineralization (cavities/pores filled with minerals. It retains original material)
  • Replacement (existing hard parts replaced by other minerals. Ex. opalized ammonite)
  • Mold (-) and Cast (+) [counterparts]
  • Carbonization (organic matter –> thin residue of carbon)
  • Amber (fossilized tree sap ; entire organism may be preserved.

historical geology (1 decks)

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