Ohio Geology

Question 1

What is the Law of Uniformitarianism?

Answer 1

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

Question 2

What is the Law of Superposition?

Answer 2

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

Question 3

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

Answer 3

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.

Question 4

What is an unconformity?

Answer 4

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

Question 5

How can erosion form an unconformity?

Answer 5

Erosion removes material and transports it to a different area.

Question 6

How is the absolute age of a rock layer determined?

Answer 6

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

Question 7

What is a fossil?

Answer 7

Fossils are the remains of once-living organisms.

Question 8

How can fossils help determine the depositional environment?

Answer 8

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

Question 9

What are five agents that can cause erosion?

Answer 9

Wind, flowing water, gravity, and animal movement.

Question 10

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

Answer 10

Clay, silt, sand, gravel and boulders.

Question 11

What is terrigenic sediment?

Answer 11

Rock particles that rivers carry from the land.

Question 12

What is biogenic sediment?

Answer 12

The shells and bones of animals

Question 13

What is limestone?

Answer 13

A sedimentary rock formed from calcium carbonate minerals.

Question 14

What is sandstone?

Answer 14

A sedimentary rock formed from sand sized grains cemented together.

Question 15

What is shale?

Answer 15

A sedimentary rock formed from clay particles cemented together.

Question 16

What is a marine environment?

Answer 16

Marine refers to deposition that occurs in saltwater seas.

Question 17

What is an aeolian environment?

Answer 17

Aeolian deposits refer to wind-carried sediment.

Question 18

What is a lacustrine environment?

Answer 18

Lacustrine deposits occur in lakes.

Question 19

What is a fluvial environment?

Answer 19

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

Question 20

What is a geologic column?

Answer 20

A chart that shows different rock layers in an area.

Question 21

How are fossils preserved by petrification?

Answer 21

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

Question 22

How are fossils preserved by molds and casts?

Answer 22

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.

Question 23

What are trace fossils?

Answer 23

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

Question 24

What is an index fossil?

Answer 24

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

Question 25

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

Answer 25

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

Question 26

What characteristics make a good index fossil?

Answer 26

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

Question 27

What is mutual bilateral symmetry?

Answer 27

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

Question 28

What is independent bilateral symmetry?

Answer 28

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

Question 29

What is a brachiopod?

Answer 29

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

Question 30

What is a trilobite?

Answer 30

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

Question 31

What are bryozoa?

Answer 31

A marine organism with branching colonies.

Question 32

What are horn coral?

Answer 32

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

Question 33

When did the last series of ice ages cover Ohio?

Answer 33

During the Pleistocene epoch.

Question 34

What is an ice age?

Answer 34

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

Question 35

What are the two types of glaciers?

Answer 35

Alpine glaciers and Continental glaciers

Question 36

Which type of glacier is associated with ice ages?

Answer 36

Continental glaciers

Question 37

What is a glacial groove?

Answer 37

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

Question 38

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

Answer 38

Kelleys Island in Lake Erie

Question 39

By what two methods can glacial deposition occur?

Answer 39

Directly from retreating ice and carried by meltwater

Question 40

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

Answer 40

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

Question 41

Sediment deposited from meltwater has what type of sorting?

Answer 41

Well sorted sediment with grain sizes of sand and gravel.

Question 42

How are glacial deposits in Ohio economically useful?

Answer 42

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

Question 43

How do glacial deposits benefit Ohio's water resources?

Answer 43

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

Question 44

How did glaciers facilitate peat formation?

Answer 44

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