PHYS 1002: Introduction to the Physics of Natural Disasters

Flashcards covering key vocabulary and concepts from the lecture notes.

Impact Energy

Heat from collisions during Earth’s formation.

Gravitational Energy

Heat from the compaction of Earth’s mass under gravity.

Radioactive Decay

Heat released as unstable isotopes break down.

Mantle Convection

The slow, circulating flow of semi-solid rock in the mantle.

Lithosphere

The rigid outer shell of Earth, broken into tectonic plates.

Asthenosphere

A somewhat softer, partially molten layer on which the plates can move.

Isostasy

The concept that the lithosphere "floats" on the asthenosphere.

Divergent boundary

Plates move apart and new crust is generated from upwelling magma.

Convergent boundary

Plates move toward each other.

Transform boundary

Plates slide horizontally past each other along faults. Crust is neither created nor destroyed.

Fault

A fracture or zone of fractures between two blocks of rock.

Focus (Hypocenter)

The point of initial rupture below ground.

Epicenter

The point directly above the focus on the surface.

Elastic Rebound Theory

As tectonic forces slowly deform the crust, rocks on either side of a locked fault bend and store elastic strain

Normal Fault

The block above the fault plane moves downward relative to the block below.

Reverse Fault

The block above the fault plane moves upward relative to the block below.

Strike-Slip Fault

Blocks on either side of the fault slide horizontally past each other (shearing motion), along a nearly vertical fault plane.

P-Waves (Primary Waves)

Compressional waves that alternately push (compress) and pull (expand) the rock in the direction the wave is traveling.

S-Waves (Secondary Waves)

Shear waves that shake the ground perpendicular to the direction of travel (side-to-side or up-and-down motions, like wiggling a rope).

Love Waves

Horizontal shear waves (side-to-side motion) confined to the surface.

Rayleigh Waves

Vertical, elliptical rolling waves (ground moves in an elliptical path, like ocean wave motion).

Magnitude

A measure of the energy released at the source of the quake, based on seismic recordings.

Intensity

A measure of the earthquake’s effects on the surface, i.e. what people feel and the damage observed.

Liquefaction

Shaking can cause the soil to temporarily behave like a liquid, undermining foundations.

Subduction Zones (Convergent Boundaries)

As an oceanic plate subducts beneath another plate, it carries water and sediments into the mantle.

Rift Zones and Mid-Ocean Ridges (Divergent Boundaries)

Plates pulling apart cause mantle material to rise. The drop in pressure (decompression) as it rises causes partial melting.

Hotspots

Volcanic regions fed by underlying mantle plumes, independent of plate boundaries.

Basaltic Magma

Low in silica (~50% SiO₂) and high in iron and magnesium (mafic). It is low-viscosity (runny) and gases escape more easily.

Andesitic to Rhyolitic Magma

Higher silica content (60–75% SiO₂), which makes the magma viscous (thick, sticky). These magmas often trap gases.

Effusive Eruptions

Outpouring of lava on the ground.

Explosive Eruptions

Violent release of gas and pyroclasts (solid fragments).

Shield Volcano

Very broad, gentle slopes, built by low-viscosity lava flows (basalt).

Stratovolcano (Composite Volcano)

Classic cone shape, steep upper slopes, made of alternating layers of lava flows, ash, and debris.

Cinder Cone

Small, steep-sided cones of volcanic cinders (scoria) and ash.

Lava Dome

A mound of viscous lava that has piled up near the vent (often in craters of larger volcanoes).

Pyroclastic Flows

Hot, fast-moving avalanches of ash, gas, and volcanic debris that sweep down volcano flanks.

Lahars (Volcanic Mudflows)

Mixes of volcanic ash/rock and water that surge downslope.

Tsunami

A series of long-wavelength, high-energy ocean waves usually caused by a sudden displacement of a large volume of water.

Stepped Leader

A faint, charged channel of ionized air (plasma) descends from the cloud in steps, heading toward the ground.

Upward Streamers

When the stepped leader nears the ground, the electric field at the surface causes positive charge to ascend from pointed objects.

Connection and Return Stroke

When a leader connects with a streamer, the circuit is completed.

Thunder

The rapid expansion of superheated air creates a shock wave.

Flood

An overflow of water that submerges land that is usually dry.

River (Fluvial) Flood

Occurs when water levels in a river, stream, or creek rise and overflow the banks, inundating nearby areas (the floodplain).

Flash Flood

A rapid onset flood, usually occurring within minutes to a few hours of intense rainfall or sudden water release.

Urban Flooding

Similar to flash floods, but specifically in cities where storm sewers and drainage might be overwhelmed.

Watershed (Drainage Basin)

The region from which water drains into a particular stream or river.

Stream Discharge

The volume of water flowing past a point in the river per unit time.

The Weather Research and Forecasting (WRF) Model

State-of-the-art numerical weather prediction system.

El Nino

One key mode of natural climate variability is the El Niño-Southern Oscillation