3rd Quarter Vocabulary - Earth Science - 8th Grade

cleavage

The way some minerals break along smooth, flat surfaces.

gravity

The force that pulls things toward each other, like how Earth pulls us down.

inertia

The tendency of an object to resist a change in motion.

orbit

The path one object takes as it moves around another, like Earth going around the Sun.

ecosystem

A community of living and nonliving things that work together.

density

How tightly packed the matter in something is.

topography

The shape and features of Earth’s surface.

glacier

A large, slow-moving sheet of ice.

energy

The ability to make things move or change.

crust

The outermost solid layer of Earth.

mantle

The layer beneath the crust, made of hot, semi-solid rock.

core

The innermost part of Earth, with a liquid outer core and solid inner core.

lithosphere

The rigid outer layer of Earth including crust and uppermost mantle.

asthenosphere

The semi-fluid layer beneath the lithosphere that allows tectonic plates to move.

tectonic plate

A piece of Earth’s lithosphere that moves over the asthenosphere.

plate boundary

The edge where two tectonic plates meet.

divergent boundary

Where two tectonic plates move apart.

convergent boundary

Where two tectonic plates move toward each other.

transform boundary

Where two tectonic plates slide past one another horizontally.

seismic wave

Energy waves that travel through Earth’s interior caused by earthquakes.

P-wave

Primary seismic wave that travels fastest through solids, liquids and gases.

S-wave

Secondary seismic wave that travels slower and only through solids.

earthquake

A sudden release of energy in Earth's crust causing seismic waves.

volcano

A vent or opening in Earth’s surface through which magma and gases erupt.

magma

Molten rock beneath Earth’s surface.

lava

Molten rock that has erupted onto Earth’s surface.

fault

A break or fracture in Earth’s crust along which movement has occurred.

mountain range

A chain of mountains formed by tectonic forces.

ocean trench

A deep, narrow depression in the ocean floor caused by subduction at convergent boundaries.

mid-ocean ridge

Underwater mountain ridge formed at divergent plate boundaries.

sedimentary rock

Rock formed by the accumulation and compaction of sediments.

igneous rock

Rock formed from the cooling of magma or lava.

metamorphic rock

Rock formed when existing rock is changed by heat, pressure, or chemical processes.

weathering

The breakdown of rocks and minerals at Earth’s surface.

erosion

The movement of weathered materials by wind, water, ice, or gravity.

deposition

The laying down of sediment carried by wind, water, or ice.

geologic time scale

A timeline that breaks up earth's 4.6 billion-year-history.

fossil

The preserved remains or traces of ancient organisms.

relative age

The age of a rock layer or fossil compared to others.

absolute age

The numerical age of a rock or fossil, often determined by radiometric dating.

superposition

Where the oldest rocks are at the bottom and the youngest rocks are at the top.

continental drift

The slow movement of continents over Earth’s surface.

sea-floor spreading

When continents spread apart and new ocean floor is made.

convection current

Movement within a fluid caused by differences in heat and density, driving plate motion.

solar system

The Sun and all the objects orbiting it (planets, moons, asteroids, comets).

star

A big, bright ball of plasma held together by gravity (e.g., the Sun).

galaxy

A large system of stars, gas and dust held together by gravity.

universe

All space, time, matter, and energy that exist.