Earthquakes

Front

Earthquake Noun

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[urth-kweyk]

Back

Earthquake

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A sudden ground movement or vibration caused by the release of energy stored in rocks along a fault.

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Example: This diagram shows an earthquake's origin (focus) below ground, with seismic waves radiating outwards. The point on the surface directly above is the epicenter.

Front

Fault Noun

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[fawlt]

Back

Fault

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A break in Earth's lithosphere along which blocks of rock move, resulting in an earthquake.

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Example: This diagram shows a fault as a fracture in Earth's crust where rock has moved, and pinpoints the hypocenter and epicenter to explain its role in an earthquake.

Front

Elastic rebound theory Noun

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[i-las-tik ree-bound thee-uh-ree]

Back

Elastic rebound theory

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The theory explaining how stress builds on a fault, causing rocks to deform and then snap back, releasing energy.

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Example: This image shows how the ground on either side of a fault bends under stress, and then suddenly snaps back to a new position, releasing energy as an earthquake.

Front

Focus Noun

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[foh-kuhs]

Back

Focus

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The point below Earth's surface where rock ruptures and an earthquake originates, releasing seismic waves.

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Example: This diagram shows the Focus as the point deep inside the Earth's crust where an earthquake originates, with seismic waves radiating outwards from it.

Front

Epicenter Noun

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[ep-i-sen-ter]

Back

Epicenter

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The point on the Earth's surface located directly above an earthquake's focus.

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Example: The epicenter is the point on the Earth's surface directly above the hypocenter (or focus), which is where an earthquake originates underground.

Front

Shallow earthquake Noun

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[shal-oh urth-kweyk]

Back

Shallow earthquake

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An earthquake with a focus less than 70 kilometers deep, which typically causes the most damage.

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Example: This diagram shows a fault rupturing close to the Earth's surface, causing a shallow earthquake. The seismic waves start near the top of the crust.

Front

Intermediate-focus earthquake Noun

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[in-ter-mee-dee-it foh-kuhs urth-kweyk]

Back

Intermediate-focus earthquake

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An earthquake with a focus located between 70 and 300 kilometers deep within the Earth's crust.

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Example: This diagram shows a subducting oceanic plate diving under a continental plate, creating the deep conditions where intermediate-focus earthquakes occur within the descending slab.

Front

Deep-focus earthquake Noun

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[deep foh-kuhs urth-kweyk]

Back

Deep-focus earthquake

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An earthquake with a focus greater than 300 kilometers deep, occurring within a subducting tectonic plate.

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Example: This diagram shows an oceanic plate subducting, or diving, under a continental plate. Deep-focus earthquakes occur far below the surface along this descending plate.

Front

Divergent Boundary Noun

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[dahy-vur-juhnt boun-dree]

Back

Divergent Boundary

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A tectonic plate boundary where two plates pull apart from each other, often creating new crust.

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Example: This diagram shows two oceanic crust plates moving apart, allowing magma from below to rise and create new crust, illustrating a divergent boundary.

Front

Convergent Boundary Noun

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[kuhn-vur-juhnt boun-dree]

Back

Convergent Boundary

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A tectonic plate boundary where two plates collide, often resulting in subduction or mountain building.

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Example: This diagram shows a dense oceanic plate colliding with and sliding under a lighter continental plate, a process that causes powerful earthquakes.