8E2.1 Earth History

Index Fossils

A fossil of an organism that existed for only a short period of geologic time and lived in many places.

Absolute dating

The actual age, in years, of a rock or fossil.

Relative dating

The age of an object or event in comparison to another object or event.

Carbon-14 dating

Carbon-14 is another radioactive substance used for finding age.

Law of superposition

States that in undisturbed sedimentary rock layers, older layers of rock lie under younger rock layers.

Radioactive dating

Measures the age of a material by comparing the amount of a radioactive substance with the amount of its decay product.

Uranium

A radioactive element that decays in lead.

Fossil

Are the preserved remains or evidence of organisms that lived in the distant past.

Extinct

A species when there are no more individuals of that species living on earth.

Geology

The study of Earth's history, processes, and structures.

Ice-cores

Is a cylinder of ice removed from an ice sheet, a deep deposit of ice and snow.

Erosion

A process by which weathered rock is picked up and moved to a new place which changes earth surface.

Unconformity

A gap in a rock layer record.

Tectonic plates

The lithosphere broken up into sections.

plate boundary

The region where 2 tectonic plates meet.

Seafloor spreading

Where 2 oceanic plates move apart, magma flows up into the space between the plates. The magma hardens to form new oceanic crust.

Fault

The break, or crack, in Earth's surface along which movement occurs.

Folding

Rock layers are squeezed together and pushed upward to form folds, or ripples in the crust forming mountains.

Uplift

The upward movement of rock layers. This occurs where 2 continental plates collide.

Magma

Melted rock beneath Earth's surface.

Lava

Melted rock that reaches Earth's surface.

Geologic evolution

The process of the Earth changing over time.