Science Chapter 4: A Trip Through Geologic Time Key Terms

Front 1

fossil

Back 1

The preserved remains or traces of living things.

Front 2

sedimentary rock

Back 2

The type of rock made from hardened sediment.

Front 3

mold

Back 3

A fossil formed when an organism buried in sediment dissolves leaving a hollow area.

Front 4

cast

Back 4

A fossil that is a solid copy of an organism's shape, formed when minerals seep into a mold.

Front 5

petrified fossil

Back 5

A fossil in which minerals replace all or part of an organism.

Front 6

carbon film

Back 6

A type of fossil consisting of an extremely thin coating of carbon on rock

Front 7

trace fossil

Back 7

A type of fossil that provides evidence of the activities of ancient organisms.

Front 8

paleontologist

Back 8

A scientist who studies fossils.

Front 9

scientific theory

Back 9

A well tested concept.

Front 10

evoluton

Back 10

The process by which living organisms gradually change over time.

Front 11

extinct

Back 11

Describes an organism that no longer exists.

Front 12

relative age

Back 12

The age of a rock compared to the ages of rock layers.

Front 13

absolute age

Back 13

The age of a rock given as the number of years since the rock formed

Front 14

law of superposition

Back 14

The geologic principle that states that in horizontal rock layers, each layer is older than the layer above it.

Front 15

extrusion

Back 15

Lava that hardens on the surface.

Front 16

intrusion

Back 16

Magma that forces its way into rock and hardens.

Front 17

fault

Back 17

A break or crack in Earth's crust.

Front 18

unconformity

Back 18

A place where an old, eroded rock surface is in contact with a newer rock layer.

Front 19

index fossil

Back 19

Fossils of widely distributed organisms that lived briefly.

Front 20

geologic time scale

Back 20

A record of the geological events and life forms in Earth's history.

Front 21

era

Back 21

One of the three long units of geologic time between the Precambrian and the present.

Front 22

period

Back 22

One of the units of geologic time into which are divided into eras.

Front 23

comet

Back 23

A ball of ice an dust that orbits the sun.

Front 24

continental drift

Back 24

The slow movement of continents over Earth's surface.

Front 25

invertebrate

Back 25

An organism without a backbone.

Front 26

vertebrate

Back 26

An organism with a backbone.

Front 27

amphibian

Back 27

A vertebrate that spends half of its life on land, and half in water.

Front 28

reptile

Back 28

A vertebrate with scaly skin that lays eggs with tough leathery shells.

Front 29

mass extinction

Back 29

When many types of organisms become extinct at the same time.

Front 30

mammal

Back 30

A vertebrate that feeds its young milk.