Earth Science Vocabulary

Pangaea

large, ancient landmass that was composed of all the continents joined together

divergent boundary

A plate boundary where two plates move away from each other.

convergent boundary

A plate boundary where two plates move toward each other.

transform boundary

A plate boundary where two plates move past each other in opposite directions

earthquake

The shaking that results from transform boundary

rift valley

A deep valley that forms where two plates move apart

Subduction

The process by which oceanic crust sinks beneath a deep-ocean trench and back into the mantle at a convergent plate boundary

uplift

the rising of regions of the Earth's crust to higher elevations

sea-floor spreading

The process by which molten material adds new oceanic crust to the ocean floor

Continental Drift Theory

the gradual movement of the continents across the earth's surface through geological time.

Fossils

Preserved remains of once-living organisms

tectonic plates

Sections of the Earth's crust that move due to convection currents.

Lithosphere

the solid, outer layer of the earth that consists of the crust and the rigid upper part of the mantle

Athenosphere

The soft layer of the mantle on which the tectonic plates move

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

relative dating

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

absolute dating

A technique used to determine the actual age of a fossil

radioactive decay

the process in which a radioactive isotope tends to break down into a stable isotope of the same element or another element

half-life

length of time required for half of the radioactive atoms in a sample to decay

inner core

A dense sphere of solid iron and nickel at the center of Earth

outer core

A layer of molten iron and nickel that surrounds the inner core of Earth

Mantle

The layer of hot, solid material between Earth's crust and core.

Crust

The thin and solid outermost layer of the Earth above the mantle

convection current

the movement of a fluid, caused by differences in temperature, that transfers heat from one part of the fluid to another; cause of tectonic plate movement

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

metamorphic rock

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

igneous rock

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

Unconformity

A break in the geologic record created when rock layers are eroded or when sediment is not deposited for a long period of time.

fossil record

information about past life, including the structure of organisms, what they ate, what ate them, in what environment they lived, and the order in which they lived

chemical weathering

The process that breaks down rock through chemical changes

Erosion

Processes by which rock, sand, and soil are broken down and carried away (i.e. weathering, glaciation)

Deposition

Process in which sediment is laid down in new locations.

physical weathering

Any process that breaks rock down into smaller pieces without changing the chemistry of the rock; typically wind and water.

dunes

mounds of wind-deposited sand

Delta

A landform made of sediment that is deposited where a river flows into an ocean or lake

coastline

Where the land meets the sea

river

large natural stream of water that runs through the land

deforestation

Destruction of forests

Urbanization

An increase in the percentage and in the number of people living in urban settlements.

Desertification

Degradation of land, especially in semiarid areas, primarily because of human actions like excessive crop planting, animal grazing, and tree cutting.

fault

A break in the earth's crust

Folding

the bending of rock layers due to stress

Law of Superposition

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

Asthenosphere

The soft layer of the mantle on which the lithosphere floats.

Geosphere

the solid part of the earth consisting of the crust and outer mantle

atmosphere

A mixture of gases that surrounds a plant

Hydrosphere

All the water at and near the surface of the earth, 97% of which is in oceans

biosphrere

area of earth where life exists

Cryosphere

Frozen water on earth

Percipitation

falling water droplets in the form of rain, sleet, snow, or hail

Evaporation

The change of a substance from a liquid to a gas

Condensation

The change of state from a gas to a liquid; causes clouds

weather

The condition of Earth's atmosphere at a particular time and place.

climate

Overall weather in an area over a long period of time

jet stream

a high-speed high-altitude airstream blowing from west to east near the top of the troposphere

Trophosphere

layer of Earth's atmosphere closest to Earth's surface (where weather takes place and where most pollution occurs)

Statosphere

Contains Ozone layer, The second layer of the atmosphere

Mesosphere

The layer of Earth's atmosphere immediately above the stratosphere; space debris usually burns here

Thermosphere

The uppermost layer of the atmosphere, in which temperature increases as altitude increases

land breeze

the flow of air from land to a body of water

sea breeze

The flow of cooler air from over an ocean or lake toward land

Currents

Mass movements of surface water produced by prevailing winds blowing over the oceans.