PHS111 Geology and Plate Tectonics: Key Concepts and Vocabulary

Fracture

A break in a rock where there is no movement.

Cleavage

The tendency of a mineral to break along flat surfaces.

Streak

The color of a mineral in powdered form.

Fine grained

Rocks that have small crystals and are difficult to see.

Coarse grained

Rocks that have large crystals that are easily visible.

Sedimentary rocks

Rocks formed from the accumulation and cementation of mineral and organic particles.

Asthenosphere

The semi-fluid layer of the mantle beneath the lithosphere.

Divergent boundary

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

Convergent boundary

A tectonic plate boundary where two plates move toward each other.

Seismic waves

Waves of energy that travel through the Earth as a result of an earthquake.

Rock

A solid material composed of one or more minerals.

Mineral

A naturally occurring inorganic solid with a definite chemical composition.

Body waves

Seismic waves that travel through the interior of the Earth.

Sial

The layer of the Earth's crust that is rich in silicon and aluminum.

Sima

The layer of the Earth's crust that is rich in silicon and magnesium.

Isostasy

The equilibrium between continental crust and the denser mantle below it.

Seismograph

An instrument that measures and records details of earthquakes.

Anticline

A type of fold that is arch-like and has its oldest rocks at the core.

Plastic strain

Deformation that results in permanent change in shape.

Focus

The actual place where seismic waves originate in an earthquake.

S-wave shadow zone

The area on the Earth's surface where S-waves do not arrive.

Richter scale

A scale used to measure the magnitude of earthquakes.

Silicon and oxygen

The elements that make up 92% of Earth's crust.

Oceanic plate and continental plate converge

An oceanic plate subducts beneath a continental plate.

Himalayan Mountains and Appalachian Mountain

Formed by the collision of tectonic plates.

Sea-floor spreading

The process by which new oceanic crust is created at mid-ocean ridges.

Continental crust

The layer of the Earth's crust that forms the continents.

Oldest rocks

Found in the continental crust.

Chains of mountains

The ocean contains chains of mountains called mid-ocean ridges.

Mid-Atlantic Ridge

A long valley that runs along the crest of the Mid-Atlantic Ridge.

Earth's crust is made of rigid plates

The theory of plate tectonics.

Columbia Plateau

Made of many layers of basalt from volcanic activity.

Rocky Mountains

Formed primarily by compressional stresses.

Sierra Nevada

A classic example of fault-block mountains.

Tensional stress

Likely to result in normal faults, rifting, and thinning of the crust.

Hanging wall slips downward

Describes a normal fault.