Chapter 4

Question 0

Can geologist use radioactive dating to find absolute ages of sedimentary layers A, B, C, D, and E? Explain why or why not.

Answer 0

No, because sedimentary rocks have many sentiments of different ages and only igneous rocks can be used with radioactive dating.

Question 1

What has the study of fossils allowed scientists to do?

Answer 1

Study Earth’s history and past environments and life.

Question 2

Can geologists use radioactive dating to find the absolute ages of the extrusion or the intrusion? Explain why or not.

Answer 2

Yes, because extrusions and intrusions are made by magma that cools, which is igneous rock.

Question 3

What is the relative age of rock layer C if the extrusion above it is 120 million years old and the intrusion is 80 million years old? Explain how you determined it’s age.

Answer 3

Rock layer C is at least 80 million years and at the greatest 120 million years because the intrusion is newer because it came through the rock and the extrusion is younger because it settles on on top of the rock.

Question 4

Explain the natural process on which radioactive dating is based.

Answer 4

Radioactive dating is based on radioactive decay of carbon-14 and the atoms of one element breakdown to form another element.

Question 5

Radioactive dating is used to…..

Answer 5

Determine the amount of radioactive element in a rock and the age of the rock.

Question 6

Explain why radioactive dating works best with igneous rocks.

Answer 6

Because radioactive elements occur naturally in igneous rock and sedimentary and metamorphic rocks have many sediments.

Question 7

Earth’s earliest atmosphere lacked the gas __________ , which is necessary for life.

Answer 7

Oxygen

Question 8

How does folding affect rock layers?

Answer 8

It puts older rock over the younger rock.

Question 9

The long span of time which covers about 88% of Earth’s history is known as…..

Answer 9

The Precambrian time

Question 10

Explain why fossils occur sedimentary rock.

Answer 10

The fossils are covered by new layers but the fossils would be damaged if they got in lava under extreme heat and pressure igneous and metamorphic rock.

Question 11

Explain why in general only the hard parts of an organism becomes fossils.

Answer 11

Because all of the other parts decompose before it becomes a fossil.

Question 12

How can unconformity affect rock layers?

Answer 12

It can cause a gap in the geologic record.

Question 13

About 250 million years ago, all the continents were joined in one landmass called…..

Answer 13

Pangaea

Question 14

What force might be responsible for the difference in the number of rock layers in location 1 with more rock layers than in location 3?

Answer 14

Weathering and erosion

Question 15

Describe how scientists have determined the approximate age of the Earth.

Answer 15

By studying moon rocks

Question 16

Geologists use the radioactive element ___________ to determine the age of remains of organisms.

Answer 16

Carbon-14

Question 17

What does the fossil record tell scientists about life over time?

Answer 17

It provides evidence about the history of life and past environments on Earth. Also, it shows how different groups of organisms have changed over time or evolution.