How is the earth changing?

volcano

A spot in the crust where magma has come to the surface

earthquake

Shaking and vibration at the surface of the earth resulting from underground movement along a fault plane or from volcanic activity

Richter scale

A scale that rates an earthquake's magnitude based on the size of its seismic waves.

Tsunami

A giant wave usually caused by an earthquake beneath the ocean floor.

Elevation

The height of land above sea level

tectonic plates

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

Ring of Fire

A major belt of volcanoes that surrounds most of the Pacific Ocean

Magma

Molten rock beneath the earth's surface

Lava

Magma that reaches Earth's surface

pyroclastic flow

a dense, destructive mass of very hot ash, lava fragments, and gases ejected explosively from a volcano and typically flowing downslope at great speed.

volcanic ash

Sand-sized particles of igneous rock that form when a spray of liquid magma is blown from a volcanic vent by escaping gas.

hot spot

a volcanically active area of Earth's surface far from a tectonic plate boundary

Molten Rock

rock that is so hot it is a very thick, slow-moving liquid.

Vent

The opening through which molten rock and gas leave a volcano

Ocean Trench

Deep valley in the ocean floor that forms along a subduction zone

Volcanic eruption

The release of material from under Earth's crust to its surface

Plate tectonics

A theory stating that the earth's surface is broken into plates that move.

Continental drift

The hypothesis that states that the continents once formed a single landmass, broke up, and drifted to their present locations

Pangaea

The name of the single landmass that broke apart 200 million years ago and gave rise to today's continents

Crust

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

Mantle

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

Outer core

the liquid layer of the Earth's core that lies beneath the mantle and surrounds the inner core

Inner core

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

mid-ocean ridge

An undersea mountain chain where new ocean floor is produced; a divergent plate boundary.

seismometer

Instrument used to measure horizontal or vertical motion during an earthquake.

subduction

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

density

the degree of compactness of a substance.

metamorphic rock

A type of rock that forms from an existing rock that is changed by heat and pressure. Found near subduction zones

igneous rock

a type of rock that forms from the cooling of molten rock at or below the surface, found near volcanoes

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, found near water or places where water was

Island chain

a formation of islands aligned above a volcanic hot spot

Viscosity

A liquid's resistance to flowing

convergent boundary

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

Divergent boundary

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

Transform boundary

The boundary between tectonic plates that are sliding past each other horizontally

Fault

a crack in the earth's crust