science study guide

Plate Tectonics and Geological History

Crust

The solid outer layer of the Earth, composed mainly of Silicon (Si), Oxygen (O), and Aluminum (Al).

Mantle

The ductile solid layer beneath the crust, consisting of Silicon (Si), Oxygen (O), and Magnesium (Mg).

Outer Core

The liquid layer of the Earth made primarily of Nickel (Ni) and Iron (Fe).

Inner Core

The solid inner layer of the Earth, composed mainly of Nickel (Ni) and Iron (Fe), due to high pressure.

Lithosphere

The rigid outer layer of the Earth, consisting of the crust and upper mantle; divided into tectonic plates.

Asthenosphere

The ductile layer of the upper mantle where tectonic plates float.

Divergent Plate Boundary

A type of plate boundary where plates move apart, creating new crust, such as mid-ocean ridges.

Convergent Plate Boundary

A type of plate boundary where plates move toward each other, leading to subduction zones and mountain ranges.

Transform Plate Boundary

A type of plate boundary where plates slide past each other without creating or destroying crust, often causing earthquakes.

Slab Pull

The gravitational force exerted by a subducting plate, which pulls the trailing plate down.

Ridge Push

The tectonic process where elevated mid-ocean ridges push tectonic plates away due to gravity.

Normal Fault

A fault where the hanging wall slides down due to tension, typically found at divergent boundaries.

Reverse Fault

A fault where the hanging wall slides up due to compression, often found in mountain ranges.

Strike-Slip Fault

A fault characterized by horizontal movement, with no vertical displacement, such as the San Andreas Fault.

Richter Scale

A scale used to measure the magnitude of earthquakes, originally developed in the 1930s.

Moment Magnitude Scale

The current scale used to measure the intensity of earthquakes based on total fault movement.

Epicenter

The surface location directly above the hypocenter where an earthquake originates.

Hypocenter

The point inside the Earth where the earthquake starts, below the surface.

Caldera

A large depression formed after a major volcanic eruption, which can fill with water to form lakes.

Volcano

An opening in the Earth's crust that allows lava, ash, and gases to escape.

Active Volcano

A volcano that has erupted historically and is expected to erupt again, with ongoing activity.

Dormant Volcano

A volcano that has not erupted in historical times but is expected to erupt in the future.

Extinct Volcano

A volcano that is unlikely to erupt again.

Viscosity of Magma

The measure of a magma's resistance to flow, influencing the explosiveness of eruptions.

Composite Volcano

A tall, layered volcano formed from explosive eruptions, typically associated with subduction zones.

Shield Volcano

A broad, gently sloping volcano formed primarily from basaltic lava, characterized by less explosive eruptions.

Cinder Cone

A small, steep-sided volcano formed from the ejection of cinders and gas.

Pyroclastic Material

Materials ejected during a volcanic eruption, including ash, tephra, and lava bombs.

Magnitude

The measure of the size or energy release of an earthquake, increasing by a factor of ten per magnitude level.

Fault

A fracture in the Earth's crust along which movement has occurred.

Modified Mercalli Intensity Scale

A scale ranging from I (not felt) to XII (total destruction) that measures the intensity of an earthquake based on its effects.