GENED Natural Disasters Final

Lithosphere

The rigid outer layer of Earth (crust and uppermost mantle). Tectonic plates

Asthenosphere

Weak layer beneath lithosphere that allows plates to move

Isostasy

Balance between earth’s crust and mantle — thicker/less dense crust floats higher

Slab pull

Sinking of cold, dense oceanic lithosphere that drives plate motion

Hotspot

stationary mantle plump that forms volcanos as plates move over it (think hawaii)

Fault

a fracture in earths crust where movement has occured

Normal Fault

extenstion, hanging wall moves down

Reverse (thrust) fault

compression, hanging wall moves up

Strike slip fault

Horizontal motion

Elastic rebound theory

stress builds until rocks snap back suddently, releasing energy as an earthquake

Hypocenter

the point INSIDE earth where the earthquake begins

Epicenter

point on the SURFACE directly above hypocenter where you feel earthquake

P-wave

fast, compressional seismic wave, travels through solids and liquids

S-wave

slower. shear wave; cant travel through liquids

Surface waves

slowest waves, travel along earth’s surface, causes most damage

Benioff Zone

A zone of deep earthquakes tracking a subducting slab

Richter magnitude

An older magnitude scale based on wave amplitude (saturates).

Moment magnitude (Mw)

Modern scale based on fault area, slip, and rock strength.

Modified Mercalli Intensity

Measures earthquake damage and human experience

Peak ground acceleration (PGA)

Maximum ground acceleration during shaking

Liquefaction

when saturated soil behaves like liquid due to shaking

Basin amplification

seismic waves intensify in soft sedimentary basins

Resonance

when building vibration matches ground shaking frequency, increasing damage

surface faulting

ground rupture directly above a fault

Retro fitting

strengthening structures to reduce earthquake damage (ex. bracing, infilling, framing, buttressing, isolating)

Alquist-Priolo Act

California law restricting building near active faults

Forecasting

estimating probabilities over long time periods

Recurrence Interval

Average time between events of a given size

Possion distribution

Statistical model for random event occurence over time

Bernoulli trial

A single event with two outcomes

Tsunami

long/large wave caused by sudden water displacement

Tsunami velocity

depends on water depth, faster in deep water

DART bouy

a deep ocean tsunami sensor

Tsunami run-up

max vertical height water reaches on land

Hazard coupling

one hazard might be triggering for another (earthquake to tsunami)

Magma

molten rock beneath earths surface

Solidus

tempurature at which rock begins to melt

Volatiles

dissolved gases (H2O, CO2) that increase explosivity

Decompression melting

melting due to pressure increase

Flux melting

melting caused by adding water

VEI (Volcanic explosivity index)

scale measuring eruption explosivity

Lahar

volcanic mudflow

Pyroclastic flow

fast-moving, hot gas and ash

Tephra

volcanic ash and rock fragments

Rotational landslide

a curved slip surface causing backward rotation

Debris flow

fast moving mixture of water, soil, and rock

Creep

slow, continuous downslope movement (trees on mountain)

Subsidence

ground sinking due to fluid removal or dissolution (fast or slow)

Troposphere

lowest atmospheric layer, weather occurs here

Adiabatic cooling/heating

Temperature change due to expansion or compression, not heat exchange

Latent heat

energy absorbed or released during phase changes of water

Coriolis force

deflection of moving air due to earths rotation (big objects; hurricanes, not tornadoes)

Albedo

fraction of sunlight reflected by a surface

ITCZ

equatorial low-pressure zone where air rises

Hadley cell

large scale circulation transporting heat from equator to mid latitudes

Tropical cyclone

a rotating storm system over warm oceans

Wind shear

change in wind speed/direction with height

Storm surge

sea level rise caused by wind and low pressure

Eye

calm, warm center of a hurricane

Drainage basin

area that drains water into a river

Discharge

volume of water flowing per unit time

Floodplain

flat land adjacent to a river that floods

Hydrograph

graph of river discharge over time

Flash flood

rapid flowing in steep terrain

Regional flood

slow flooding over large areas

Sinousity

degree of river meandering

Eustatic sea level

global average sea level change

Sea level fingerprint

regional pattern of sea level change due to ice melt

Thermal expansion

water expanding as it warms

Ice sheet

large mass of land based ice

Ice shelf

floating extenstion of ice sheet

Satellite altimetry

measuring sea level from space

Tide guage

coastal sea level measurement device

Asteroid

rocky object, usually from asteroid belt

Comet

icy body from outer solar system

Kinetic energy

energy of motion (1/2mv²)

Simple crater

small, bowl shaped crater

Complex crater

large crater with central uplift

Supercell

tall, rotating thunderstorm

Angular momentum

conservation causes rapid spinning

Catastrophe bond

financial instrument transferring disaster risk to investors

Trigger

condition that causes bond payout

Systemic risk

risk that effects the entire financial system