Earthquakes & Volcanoes Study Guide

Study Notes

Stress: The force that acts on a rock to change its shape or volume.
Tension: Pulling the Earth's crust, getting thinner in the middle.
Compression: Squeezing rock until it folds or breaks.
Shearing: Force pushes a mass of rock in two opposite directions.
Fault: A fracture in Earth's crust.
Earthquake: Shaking and trembling from the movement of Earth's crust plate boundaries.
Seismic Waves: Energy carried from an earthquake's focus.
Magnitude: Measurement of an earthquake's strength (a single number based on size).
Tsunami: A giant wave caused by an underwater earthquake.
Viscosity: How thick a liquid is and how easily it pours.
Aa Lava: Slow-moving, cooler lava that dries rough.
Pahoehoe Lava: Fast-moving, hotter lava that dries smooth or ropey.
Pyroclastic Flow: Hot, dense mixture of ash, gas, and rock fragments from a volcano.
Magma: Molten material in the Earth.
Lava: Molten material on the Earth's surface.
Volcano: A weak spot in the crust where magma comes to the surface.
Hot Spot: An area where lava frequently erupts at the surface, independent of plate boundaries.
Focus (Earthquake): Point in the crust where an earthquake begins.
Epicenter (Earthquake): Point on the Earth's surface directly above the focus.
Seismograph: Instrument used to record ground movements caused by seismic waves.

Primary (P-waves): Compress and expand, travel through solids and liquids.
Secondary (S-waves): Vibrate side-to-side and up-and-down, travel only through solids.
Surface Waves: Travel along the surface, cause the most damage.