GEOL 118 Exam 1

Chapters 1-4 (updated thru ch 3)

natural hazard

a natural event that poses potential disaster

natural disaster

a natural event that occurs from a natural hazard; widespread impact

rapid-onset disaster

a disaster with no warnings or signs; earthquakes usually

slow-onset disaster

a disaster that take multiple days or weeks to develop; floods

very slow-onset disaster

a disaster that develops over months, years, or decades, also know as stealth disasters; sea level rises, drought, groundwater depletion

primary disaster

destruction from a natural hazard event

secondary disaster

triggered by a primary disaster; tsunamis from an earthquake (always secondary)

tertiary disaster

long-term societal disasters due to primary and secondary disasters

frequency

how often a disaster happens

recurrence interval (RI)

the average time between events of a certain size (requires a historical record), __=t/N

annual probability (AP)

the likelihood that an event will happen in a given year; 1/RI=AP

evacuees

people that are displaced within the country

refuguees

people that are displaced outside of the country/into another country

exposure

the likelihood of disaster impacts

vulnerability

how bad the disaster will hurt the community if it happens

risk

probability AND size of loss due to a natural disaster; can increase due increasing population, climate change, and land modification

disaster watch

tells when to look out for a disaster

disaster warning

tells that the disaster is happening now

disaster insurance

decreases the impact of disasters on an individual or a community; makes them less vulnerable

atmosphere

made of nitrogen and oxygen, water vapor (holds energy, fuels severe weather)

weather

short-term atmospheric changes

climate

long-term atmospheric changes

hydrosphere/cryosphere

70% of earth’s surface, 97% saltwater, 3% freshwater, ice in cold areas, sea level changes when ice melts or evaporates

geosphere

mostly solid, rocky, dense matter, continents and oceans; oceans are a low zone, surface moves and changes

biosphere

all living things on earth, biological activity greatly affects atmosphere

internal energy

leftover heat from formation of earth, deeper=hotter, heat from radioactive decay, drives movement of the solid earth

external energy

radiation from the sun, heats land & water surfaces, causes winds

gravity

potential energy, causes land movement, rainfall, and river flow

convection

the heating and cooling that drives motion in the earth and above the surface; winds, mantle material, etc.

core

dense iron material in the earth (egg yolk), makes a magnetic field from the outer part churning

mantle

rocky material surrounding the core (egg whites), mostly low-silica

crust

thin layer, mantle melting, surface (egg shell)

mineral

a material that has recurring, regular atomic patterns (naturally occurring, generally inorganic, homogeneous, crystalline solid, definable composition)

rock

holds itself together (coherent), naturally occurring, aggregate of minerals (many mineral grains attached to one another)

crystalline rocks

minerals packaged together

clastic rocks

made from fragments of minerals (cemented together)

igneous rock

a type of rock that forms when molten rock cools and hardens

silica-rich magma

viscous and doesn’t release pressure easily (kaboom)

low-silica magma

runny magma that flows easily

physical weathering

when rocks break into fragments called clasts

chemical weathering

when the minerals in rocks dissolve and new minerals form (ex: clay, mud, etc.)

quartz

resists weathering, becomes sands

sedimentary rock

formed from sediments: accumulation of clasts, precipitation of minerals from dissolved stuff in water

beds

near-horizontal layers of deposited sediment

metamorphic rock

existing rock that transformed through heat and pressure, deep burial and/or magma intrusions, may develop a foliated texture (like a book)

slate

when small clay minerals become foliated

schist

when larger mica minerals (a group of natural silicate minerals that split easily into very thin, flexible sheets) become foliated

seismic waves

earthquake vibrations, speeds vary, refect when crossing into different layers of earth

s-waves

waves that cannot go through liquid, but can go thru solid, shearing motion perpendicular to travel direction

p-waves

waves that can thru both liquid and solid, but decrease in velocity, motion parallel to travel direction

oceanic crust

7-10km thick, silica-poor rock, runny, basalt (dense)

continental crust

25-70km thick; silica-rich, igneous, sedimentary, and metamorphic rock

lithosphere

rigid, upper unit (crust and some upper mantle)

asthenosphere

below the lithosphere, hotter; plastic flow (still solid!!!), allows lithosphere to glide on top

continental drift

the theory that there was once a super continent (Pangea) and the plates shifted and spread apart so now there are 7 continents, Alfred Wegener

mid-atlanic ridge

center of the atlantic ocean, central valley, fracture zones, where new crust is created, ocean is expanding

plate tectonic theory

earth's crust is broken into huge pieces that slowly move over the soft, hot mantle

divergent boundary

boundary where plates are moving apart from each other (rift valley exists)

convergent boundary

boundary where plates are coming towards each other (mountains or trenches)

transform boundary

boundary where plates slides horizontally past each other (san andreas fault)

subduction

when the older plate sinks down into the mantle at a convergent boundary

continental rift

when two plates split apart (divergent), ex: east african rift (many volcanoes, earthquakes, and new lakes)

hot spots

volcanoes not at plate boundaries (ex: hawaii)

uniformitarianism

the theory that in the past, the earth works the same as it does now, "we infer what happened in the past, “the present is the key to the past”

geological time scale

a time scale based on fossils and rocks, figure out which fossils are older based on what rock they’re found in, maps evolution and extinction over time

seismic waves

caused by build up and release of stress (energy) in the earth, elastic rebound

stick-slip motion

fault is locked (high friction), tectonic motion causes rocks to bend, stress builds, stress causes materials to break, fault slips, rock snaps back, seismic waves released, cycle repeats

fault

a fracture in rock that has moved/slipped

normal fault

hanging wall moves down fault line plane relative to footwall (divergent boundaries, can create rifts)

reverse fault

hanging wall moves up the fault plane relative to the footwall

thrust fault

reverse fault with a small angle (common at convergent boundaries, subduction zones)

strike-slip fault

two sides scrape past each other (san andreas fault, transform boundary)

mainshock

largest earthquake of the sequence

aftershock

cluster of smaller earthquakes following the mainshock (10x smaller, frequency diminishes over time, can be damaging)

foreshock

cluster of small earthquakes that may precede a mainshock (not always)

body waves

waves that travel thru the interior of the earth

surface waves

waves that travel along the surface of the earth

r-waves

vertical motion of rolling undulations, like waves in a pond

l-waves

horizontal shearing motion, like a snake

refraction

a wave’s travel direction changes as the wave passes thru a change in rock type

reflection

bounce off different types of rocks, some bounce off the top of the mantle

attenuation

when waves usually weaken with increasing distance from the focus

amplification

if waves move into a weaker material, the wave amplitude often increases

seismometer/seismograph

a device that measures and records ground motion (seismic waves, vertical and NSEW motion measured)

seismogram

the record of an earthquake produced by a seismograph

s-p time

tells the distance of a seismometer from an earthquake, you can triangulate the focus using 3 seismometers

richter scale

a scale that is based on amount of ground motion at a seismometer and the distance from that to the epicenter (obsolete now, M_L)

moment magnitude scale

a scale that is based on areal size of the fault slip, average amount of slip, and rock rigidity, represents energy released by the earthquake (used today, M_w)

magnitude

a logarithmic scale used to measure earthquakes (10 is not the max, ex: M_w7 is 32x more energy than M_w6)

modified mercalli intensity scale

a scale that measures intensity according to perception of shaking using historical data or reports from people (uses roman numerals I-XII, intensity maps)

divergent boundary seismicity

mid-ocean divergent boundaries, normal and transform faults, shallow-focus earthquakes, mostly far from population centers, earthquakes here have little societal impact (ex: atlantic ocean)

transform boundary seismicity

population centers near continental transform boundaries are at a risk, shallow-risk earthquake are common (ex: california)

convergent boundary seismicity

shallow-focus and large slip areas generate megathrust earthquake, shallow, intermediate, and deep-focus earthquakes (ex: japan, chile, etc.)

megathrust earthquake

an earthquake that has a M_W > 8.6 (the strongest type of earthquake)

intraplate seismicity

earthquakes occur along ancient, pre-existing faults, usually shallow-focus, NOT on a plate boundary

induced seismicity

human caused, caused by disposal wells that inject wastewater into the ground (especially hydrofracturing), water pressure from reservoirs, and fracking, increased water pressure weakens existing faults

ground ruptures

wide-open fissures from this are uncommon, surface ruptures tear apart infrastructure, liquefaction, shaking causes most fatalities

ground shaking

each type of seismic wave creates unique ground motion, surface waves are more destructive, shaking severity depends on magnitude, surface waves, and distance from focus

peak ground acceleration

acceleration is the key number, not the distance of movement, compared to the acceleration by gravity

shaking duration

depends on: in larger earthquakes, the fault slips for longer, so shaking lasts longer; distance from fault break (greater distance = longer duration)