Rock & Fossil Record

Question 1

uniformitarianism

Answer 1

a principle that states that geologic processes that occurred in the past can be explained by current geologic process.

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 the younger ricks 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 thus a different atomic mass)

Question 8

radioactive decay

Answer 8

the process in which a radioactivity 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 that is 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 death of every member of a species

Question 16

Jurassic period

Answer 16

of, denoting, or formed in the second period of the Mesozoic era, between the Triassic and Cretaceous periods, lasting for 55 million years during which dinosaurs and ammonites flourished.

Question 17

cretaceous period

Answer 17

the period between 145.5 and 65.5 million years ago,* the last period of the Mesozoic Era, following the Jurassic and ending with the extinction of the dinosaurs (except birds).

Question 18

Devonian period

Answer 18

a geologic period and system of the Paleozoic, spanning 60 million years from the end of the Silurian, 419.2 million years ago (Mya), to the beginning of the Carboniferous, 358.9 Mya. It is named after Devon, England, where rocks from this period were first studied.

Question 19

Quaternary period

Answer 19

The Quaternary period is the name for the time in which we live. It spans the two most recent geologic epochs, the Pleistocene and the Holocene. Fossils from the Holocene epoch are like the animals living today, whereas Pleistocene fossils are much like living animals but with some differences.

Question 20

permain period

Answer 20

The Permian period lasted from 299 to 251 million years ago* and was the last period of the Paleozoic Era. The distinction between the Paleozoic and the Mesozoic is made at the end of the Permian in recognition of the largest mass extinction recorded in the history of life on Earth.