GEOL EXAM 5 NEW

Hypocenter

The precise point within the Earth where an earthquake rupture initiates.

Epicenter

The point on the Earth's surface directly above the hypocenter.

Longshore Current

A current that flows parallel to the shoreline, created by waves hitting the coast at an angle.

Longshore Drift

The process of sediment being transported along the coast by longshore currents.

Wave Refraction

The bending of waves as they enter shallow water, caused by different parts of the wave front moving at different speeds.

Headland Erosion Sequence

A progression of coastal features starting with a headland, then sea caves, sea arches, sea stacks, and finally sea stumps.

P-Wave

A primary, compressional seismic body wave that travels through solids, liquids, and gases.

S-Wave

A secondary, shear seismic body wave that only travels through solid materials.

Moment Magnitude Scale

A logarithmic scale that measures the total energy released by an earthquake.

Modified Mercalli Scale

A qualitative scale that measures the intensity of an earthquake based on observed ground shaking and damage.

Liquefaction

A process where saturated, unconsolidated sediment loses strength and behaves like a fluid during earthquake shaking.

Resonance Frequency

The natural frequency at which a structure vibrates; matching this with seismic waves can lead to increased structural damage.

Unreinforced Masonry

Building construction using brick or stone without steel reinforcement, which is highly susceptible to collapse during earthquake shaking.

Drop, Cover, and Hold On

The recommended safety procedure during an earthquake to protect against falling objects and structural collapse.

Crust

The outermost, solid layer of the Earth, composed primarily of silicate rocks.

Mantle

The thick layer of rock below the crust, composed of silicate minerals rich in iron and magnesium.

Outer Core

The liquid layer of the Earth's interior composed mostly of iron and nickel, responsible for generating the magnetic field.

Inner Core

The solid, innermost layer of the Earth, composed of iron and nickel.

Lithosphere

The rigid outer layer of the Earth consisting of the crust and uppermost mantle.

Asthenosphere

The ductile, partially molten layer of the upper mantle below the lithosphere that facilitates plate movement.

Ophiolite Complex

A sequence of oceanic crust and mantle rocks including deep-sea sediments, pillow basalts, sheeted dikes, gabbro, and ultramafic rock.

Moho

The Mohorovičić discontinuity, representing the boundary between the Earth's crust and the mantle.

Hydrothermal Vent

An opening in the seafloor that emits superheated, mineral-rich water, often supporting unique chemosynthetic ecosystems.

Transform Boundary Earthquake

Earthquakes typically occurring at shallow depths caused by horizontal sliding between plates.

Divergent Boundary Earthquake

Earthquakes typically occurring at shallow depths caused by tensional stress as plates move apart.

Subduction Zone Earthquake

Earthquakes that can occur at great depths (up to 700 km) as the cold, brittle oceanic plate descends into the mantle.

Oceanic Crust Formation

Formed at mid-ocean ridges by upwelling magma; it is composed of basalt and gabbro.

Oceanic Crust Destruction

Destroyed at subduction zones where the denser oceanic plate is forced back into the mantle.

Oceanic Crust Age

The current oceanic crust is generally less than 200 million years old due to constant recycling by plate tectonics.

Seafloor Features

Major features include the continental shelf, continental slope, continental rise, abyssal plain, mid-oceanic ridge, and deep-ocean trenches.

Seismic Reflection

The technique of bouncing seismic waves off boundaries between Earth layers to image subsurface structure.

Seismic Refraction

The technique of measuring the change in seismic wave velocity as waves pass through different Earth materials to determine layer density and composition.