Fossil Record

Question 1

uniformitarianism

Answer 1

a principle that states that geologic processes that occurred in the past can be explained by geological processes

Question 2

catastrophic

Answer 2

a principle that states that geologic change occurs suddenly

Question 3

paleontology

Answer 3

the scientific study of fossils

Question 4

relative dating

Answer 4

any method of determining whether an event or object is older or younger than other events or objects

Question 5

absolute dating

Answer 5

any method of measuring the age of an event or object in years

Question 6

superposition

Answer 6

a principle that states that younger rocks lie above older rocks if the layers have not been disturbed

Question 7

isotope

Answer 7

an atom that has the same number of protons (or the same atomic number) as other atoms of the same element do but that has a different number of neutrons (and a different atomic mass)

Question 8

radioactive decay

Answer 8

the process in which a radioactive isotope tends to break down into a stable isotope of the same element or another element

Question 9

half-life

Answer 9

the time needed for half of a sample of a radioactive substance to undergo radioactive decay

Question 10

fossil

Answer 10

the remains or physical evidence of an organism preserved by geological process

Question 11

trace fossil

Answer 11

a fossilized mark formed in soft sediment by the movement of an animal

Question 12

mold

Answer 12

a mark or cavity made in a sedimentary surface by a shell or other body

Question 13

cast

Answer 13

a type of fossil that forms when sediments fill in the cavity left by a decomposed organism

Question 14

unconformity

Answer 14

a break in the geologic record created when rock layers are eroded or when sediment is not deposited for a long period of time

Question 15

mass extinction

Answer 15

The extinction of a large number of species within a relatively short period of geological time, thought to be due to factors such as a catastrophic global event or widespread environmental change that occurs too rapidly for most species to adapt.

Question 16

Jurassic period

Answer 16

lasting for 55 million years during which dinosaurs and ammonites flourished.

Question 17

Cretaceous period

Answer 17

a period of the Mesozoic Era, from 140 million to 65 million years ago, characterized by the greatest development and subsequent extinction of dinosaurs and the advent of flowering plants and modern insects.

Question 18

Devonian period

Answer 18

a geological time during which a system of rocks formed. The trees are particularly important

Question 19

Quaternary period

Answer 19

a current period of geologic time, which began about 1.8 million years ago. … The Quaternary period is the name for the time in which we live.

Question 20

Permian period

Answer 20

a Gymnosperms evolved, the first modern conifers appeared, and reptiles diversified. The Permian Period ended with the largest known mass extinction in the history of life. It wiped out nearly 90 percent of known marine life forms.