Age of Rocks

Question 1

What are two ways geologists describe how old a rock is?

Answer 1

relative age dating and absolute age dating

Question 2

What is relative age?

Answer 2

The age of a rock compared to the ages of other rocks

Question 3

What is absolute age

Answer 3

The number of years since a rock formed.

Question 4

What is the most common type of absolute dating?

Answer 4

Radiometric dating

Question 5

Describe the law of superposition

Answer 5

Newer rock layers will be at the top, and older rock layers will be at the bottom.

Question 6

What is an index fossil?

Answer 6

An extinct organism that existed for a short period of time and is very common all over the world.

Question 7

2 examples of index fossils

Answer 7

trilobites and ammonites

Question 8

most of the earth’s geologic record has been lost to:

Answer 8

weathering and erosion

Question 9

define unconformity

Answer 9

a gap or change in the geologic record and shows where rock layers have been lost to erosion

Question 10

how do you show unconformity on a diagram

Answer 10

a black squiggly line

Question 11

define faulting

Answer 11

when a break in the crust forces a rock to move along the break

Question 12

how does faulting affect rock layers

Answer 12

layers become uneven

Question 13

what’s folding

Answer 13

when layers of rock get smushed and pushed up and down

Question 14

What is the difference between an intrusion and extrusion?

Answer 14

Intrusion - When igneous rock (magma) push into a rock unit
Extrusion - when lava hardens on the surface and layers of sedimentary rock gets piled on top

Question 15

How old is an intrusion compared to the rocks around it?

Answer 15

Intrusions are younger than the rocks it pushed into

Question 16

If a scientist finds a rock with a fish in it, what does that tell the scientist about the environment?

Answer 16

That the area was once covered by water.