Natural Hazards and Plate Tectonics Review

Comprehensive vocabulary flashcards covering natural hazards, Earth's internal structure, plate tectonics, earthquakes, tsunamis, volcanism, and mass movements based on the lecture transcript.

Natural hazard

A naturally occurring event or process that has the potential to cause damage, injury, or loss of life.

Disaster

A hazard that causes significant damage, loss of life, or disruption to society.

Catastrophe

An extremely severe disaster with widespread destruction and long-lasting impacts.

Vulnerability

How susceptible people, buildings, or communities are to damage from a hazard.

Risk

The combination of the probability of a hazard occurring and its consequences.

Mitigation

Actions taken to reduce the impacts of natural hazards before they occur, such as building earthquake-resistant structures or land-use planning.

Magnitude

A measure of the size or strength of a natural event.

Frequency

How often a natural event occurs.

Return period

The average amount of time between events of a given magnitude.

Compositional Layers

The categorization of Earth's interior by chemical makeup, consisting of the crust, mantle, and core.

Lithosphere

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

Asthenosphere

A weak, partially molten layer beneath the lithosphere that allows tectonic plates to move.

Mesosphere

The stronger lower mantle located beneath the asthenosphere.

Outer Core

A layer of liquid iron and nickel whose movement generates Earth's magnetic field.

Inner Core

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

Seismic waves

Waves of energy released during an earthquake used by scientists to determine Earth's interior structure.

Differentiation

The gravity-driven process in which dense materials (like iron) sank to Earth's center while lighter materials rose toward the surface roughly $-4.6$ billion years ago.

Alfred Wegener

The scientist who proposed the Continental Drift Hypothesis, suggesting that the continents were once joined as the supercontinent Pangaea.

Sea-floor spreading

The formation of new oceanic crust at mid-ocean ridges, a concept proposed by Harry Hess.

Magnetic reversal

A reversal of Earth's magnetic field that creates symmetrical magnetic stripes on both sides of a mid-ocean ridge.

Plate Tectonics

The theory that Earth's lithosphere is divided into large rigid sections driven by mantle convection, ridge push, and slab pull.

Divergent plate boundary

A boundary where two plates move apart, forming mid-ocean ridges or continental rift valleys, and creating new crust.

Convergent plate boundary

A boundary where two plates move toward one another, resulting in subduction or mountain building, and the destruction of crust.

Transform boundary

A boundary where two plates slide past one another, such as the San Andreas Fault, neither creating nor destroying crust.

Elastic rebound

The process where rocks slowly bend as stress builds, then suddenly snap back during an earthquake.

Stick-slip behavior

A behavior where friction causes rocks to stick until stress overcomes it, producing sudden movement.

Stress and Strain

$\text{Stress}$ is the force acting on rock, while $\text{Strain}$ is the resulting deformation.

Focus (Hypocenter)

The point inside Earth where an earthquake begins.

Epicenter

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

Seismograph

The instrument used to record earthquakes, producing a tracing known as a seismogram.

P-waves (Primary waves)

The fastest seismic waves that compress/expand material and can travel through solids, liquids, and gases.

S-waves (Secondary waves)

Seismic waves that move material side-to-side and can only travel through solids; they cannot travel through the liquid outer core.

Surface waves

The slowest seismic waves that produce large ground movements and usually cause the most damage.

Moment Magnitude Scale ($Mw$)

The scale used to measure the specific energy released by an earthquake.

Modified Mercalli Intensity ($MMI$) Scale

The scale used to measure the shaking and damage experienced at a specific location.

Liquefaction

A phenomenon where water-saturated soil temporarily behaves like a liquid during earthquake shaking.

Tsunami

A series of large ocean waves caused by sudden displacement of water, most commonly by undersea subduction-zone earthquakes.

Wavelength

The distance between two successive wave crests.

Wave amplitude

The height of a wave measured from its normal water level to its crest.

Decompression melting

Magma formation caused by a decrease in pressure as hot mantle rock rises, typically at divergent boundaries and hotspots.

Flux melting

Magma formation caused by adding water to hot rock, lowering its melting temperature, typically at subduction zones.

Hotspot

A location where hot mantle rises through a tectonic plate away from boundaries, such as Hawaii or Yellowstone.

Viscosity

A measure of how resistant magma is to flowing; high silica content results in higher viscosity.

Basalt

A type of magma with low silica, high temperature, and low viscosity, commonly associated with effusive eruptions.

Rhyolite

A type of magma with high silica, low temperature, and high viscosity, commonly associated with explosive eruptions.

Volatiles

Dissolved gases in magma, primarily water vapor, carbon dioxide, and sulfur dioxide.

Lava dome

A mound of thick, sticky lava that piles up over a volcanic vent and can collapse to generate pyroclastic flows.

Pyroclastic flow

The deadliest volcanic hazard, consisting of a fast-moving, extremely hot mixture of gas, ash, and rock.

Lahar

A volcanic mudflow made of ash mixed with water, which can travel far from a volcano.

Volcanic-tectonic (VT) earthquake

A brittle-rock earthquake caused by fracturing as magma moves.

Volcanic Explosivity Index ($VEI$)

A scale used to measure the size and explosiveness of a volcanic eruption.

Rockfall

A mass movement involving rocks falling freely from a steep slope.

Landslide

A mass movement where rock or soil slides downhill.

Debris flow

A fast-moving mixture of water, rock, and soil.

Creep

The extremely slow downhill movement of soil.