Ohio Geology Flashcards

1
Q

What is the Law of Uniformitarianism?

A

Current geologic processes are the same as those in the past.

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2
Q

What is the Law of Superposition?

A

Unless the layers are deformed, a rock layer below is older than a rock layer above.

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3
Q

How can rock structures help determine the relative age of a rock layer?

A

Ripple mark crests point up. Sand dunes make curved lines towards the bottom of the layer. Graded bedding has larger particles on the bottom of the layer.

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4
Q

What is an unconformity?

A

A break in the rock record. Geologic evidence is missing.

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5
Q

How can erosion form an unconformity?

A

Erosion removes material and transports it to a different area.

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6
Q

How is the absolute age of a rock layer determined?

A

Radiometric dating uses the decay rates of radioactive elements to determine how much time has passed since deposition.

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7
Q

What is a fossil?

A

Fossils are the remains of once-living organisms.

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8
Q

How can fossils help determine the depositional environment?

A

Certain organisms live in a well-defined environment. Presence of those fossils indicate the environment where the organism lived and died.

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9
Q

What are five agents that can cause erosion?

A

Wind, flowing water, gravity, and animal movement.

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10
Q

What is the order of sediment size from smallest to largest?

A

Clay, silt, sand, gravel and boulders.

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11
Q

What is terrigenic sediment?

A

Rock particles that rivers carry from the land.

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12
Q

What is biogenic sediment?

A

The shells and bones of animals

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13
Q

What is limestone?

A

A sedimentary rock formed from calcium carbonate minerals.

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14
Q

What is sandstone?

A

A sedimentary rock formed from sand sized grains cemented together.

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15
Q

What is shale?

A

A sedimentary rock formed from clay particles cemented together.

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16
Q

What is a marine environment?

A

Marine refers to deposition that occurs in saltwater seas.

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17
Q

What is an aeolian environment?

A

Aeolian deposits refer to wind-carried sediment.

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18
Q

What is a lacustrine environment?

A

Lacustrine deposits occur in lakes.

19
Q

What is a fluvial environment?

A

Fluvial environments refer to river deposits within the channel or into another body of water.

20
Q

What is a geologic column?

A

A chart that shows different rock layers in an area.

21
Q

How are fossils preserved by petrification?

A

Petrification is mineral replacement of the original material. Ex: petrified wood

22
Q

How are fossils preserved by molds and casts?

A

When the organism dies, it can get buried in sediment and leave a cavity in the shape of the organism called a mold. Casts are made when the mold is filled with a mineral.

23
Q

What are trace fossils?

A

Evidence such as footprints, burrows and coprolites that indicate a living organism was in the area.

24
Q

What is an index fossil?

A

An organism that occurs only in rock layers of a particular age.

25
Q

How can the lifespans of organisms help determine the age of a rock layer?

A

A rock layer’s age can only be an age that all fossils’ lifespans have in common.

26
Q

What characteristics make a good index fossil?

A

A good index fossil has features that are easily recognized, distinguishable from similar organisms, and a short lifespan.

27
Q

What is mutual bilateral symmetry?

A

A line dividing an organism into two equal parts (between valves)

28
Q

What is independent bilateral symmetry?

A

A line dividing a section of an organism into two identical parts (within a valve)

29
Q

What is a brachiopod?

A

A marine organism with an upper shell and lower shell attached to a stem

30
Q

What is a trilobite?

A

An extinct marine organism with a carapace over the forepart and a segmented hind section divided into three lobes.

31
Q

What are bryozoa?

A

A marine organism with branching colonies.

32
Q

What are horn coral?

A

A marine organism with cone-shaped chambers in a colony.

33
Q

When did the last series of ice ages cover Ohio?

A

During the Pleistocene epoch.

34
Q

What is an ice age?

A

A period of extended low temperatures that cause large areas of the Earth to be covered with ice sheets.

35
Q

What are the two types of glaciers?

A

Alpine glaciers and Continental glaciers

36
Q

Which type of glacier is associated with ice ages?

A

Continental glaciers

37
Q

What is a glacial groove?

A

A elongated channel preserved in rock that formed when heavy ice sheets with embedded boulders carved the bedrock as they passed.

38
Q

Where in Ohio is a world-famous example of glacial grooves?

A

Kelleys Island in Lake Erie

39
Q

By what two methods can glacial deposition occur?

A

Directly from retreating ice and carried by meltwater

40
Q

Sediment deposited directly from retreating glaciers has what type of sorting?

A

Poorly sorted sediment with grain sizes ranging from boulders to clay.

41
Q

Sediment deposited from meltwater has what type of sorting?

A

Well sorted sediment with grain sizes of sand and gravel.

42
Q

How are glacial deposits in Ohio economically useful?

A

They can be used as construction materials or clay for pottery.

43
Q

How do glacial deposits benefit Ohio’s water resources?

A

The Great Lakes formed from glacial activity during the last ice age. Glacial deposits in former stream and river channels form many current aquifers.

44
Q

How did glaciers facilitate peat formation?

A

Dead plant material falls to the bottom of glacial lakes that do not provide the correct acidic and anaerobic conditions for full decay.