Earth Science Unit Review

Continental Drift Theory

the idea that continents slowly shift their positions due to movement of the tectonic plates on which they ride

Evidence of Continental Drift

Fossils, climate, rocks, glacial deposits

divergent boundary

The boundary between two tectonic plates that are moving away from each other

convergent boundary

A tectonic plate boundary where two plates collide, come together, or crash into each other.

Ocean trenches are associated with

plate subduction

Mid-ocean ridges are

divergent plate boundaries

San Andreas Fault

A major geological fault in California formed by a sliding transform boundary.

subduction zone

in tectonic plates, the site at which an oceanic plate is sliding under a continental plate.

radiometric dating

method used to determine the age of rocks using the rate of decay of radioactive isotopes

Law of Uniformitarianism

the idea that the same processes we see occurring now also occurred in the past

Law of Superposition

The top rock layer and its fossils is the youngest and the bottom is the oldest.

convection currents in the mantle

Most geologists think that the movement of Earth's plates is caused by

Law of Unconformity

break in the geologic record that is made when rock layers eroded or when sediment is not deposited for a long period of time. often due to erosion

Law of Cross-Cutting Relationships

the principle that a fault or body of rock is younger than any other body of rock that it cuts through

absolute dating

A technique used to determine the actual age of a fossil

relative dating

Method of determining the age of a fossil by comparing its placement with that of fossils in other layers of rock

index fossil

a fossil known to have lived in a particular geologic age that can be used to date the rock layer in which it is found

Strata

layers of rock, representing various periods of deposition

Geologic Timeline

The summary of Earth's history, divided into intervals of time defined by major events or changes on Earth.

Era

the largest division of geologic time

igneous rock

a type of rock that forms from the cooling of molten rock at or below the surface

Metamorphic Rock

A type of rock that forms from an existing rock that is changed by heat, pressure, or chemical reactions.

sedimentary rock

A type of rock that forms when particles from other rocks or the remains of plants and animals are pressed and cemented together

The law of original horizontality states that:

sedimentary rocks are originally deposited as horizontal bodies

inclusions

Any part of a previous rock layer, like a piece of stone, is older than the layer containing it.

Lateral Continuity

Sedimentary layers or lava flows extend sideways in all directions until they thin out or reach a barrier