Unit 1 - 8th Grade Science Review

Vocabulary flashcards covering geologic dating methods, rock types, Earth's history, and the Law of Superposition for 8th Grade Science.

Absolute Dating

Finds the actual/numerical age of a rock or fossil in years using radioactive isotope decay.

Geological Time Scale

A timeline showing the order of Earth’s history from oldest to youngest.

Igneous Rock

Rock formed when magma or lava cools and hardens.

Sedimentary Rock

Rock formed when layers of sediment are compacted and cemented together; fossils are most commonly found here.

Metamorphic Rock

Rock changed by heat and pressure without melting.

Molten Rock

Melted rock; includes magma and lava.

Magma

Molten rock that is below Earth’s surface.

Lava

Molten rock that is above Earth’s surface.

Pangea

The ancient supercontinent in which Earth’s continents were once joined together.

Alfred Wegener

The scientist who proposed continental drift, the idea that continents move over time.

Erosion

The movement of weathered rock and sediment by water, wind, ice, or gravity.

Weathering

The breaking down of rock into smaller pieces at or near Earth’s surface.

Deposition

The dropping or settling of sediment in a new location.

Index Fossil

Fossil from an organism that lived for a short period of geologic time but was common and widespread; used for relative dating.

Rock Stratum

A distinct layer of rock or sediment formed during a particular time in Earth’s history.

Relative Dating

Determines whether rocks or fossils are older or younger than others; gives an order, NOT an exact age.

Rock Cycle

The continuous process through which rocks change from one type to another.

Law of Superposition

In undisturbed sedimentary rock layers, the youngest layer is on top and the oldest layer is at the bottom.

Trilobites

Organisms commonly used as index fossils for portions of the Paleozoic Era.

Cenozoic Era

The current geologic era in which we live.