Earthquakes and other Disasters

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natural hazard

natural process on earth that can potentially threaten humans in some way; not all their impacts are negative- volcanic soil, floods and hurricanes deposit nutrients

Natural disaster

natural hazards that cause massive negative impacts to society in some way; measures by fatalities and economic loss

where are disasters with highest economic loss occurring?

in countries like the U.S. where there is a lot of infrastructure; urbanization-can make a disaster in a city like ny much worse

New Madrid Earthquake series

1811-1812, intra-plate earthquake, ancient buried rift

crust (chemical property)

outermost layer of the earth, includes the oceans and oceanic crust and continental crust; least dense and most thin

earth is separated into a series of concentric layers based on their...

chemical and physical properties

mantle (chemical property)

made of rocky silicates denser than the crust

core (chemical property)

center of the earth made of dense metals

rheology

refers to the way in which material behaves in response to an applied force and determines the way the earth's physical properties are split up.

hydrosphere (physical property)

made up of the liquid of the oceans on the Earth's surface

lithosphere (physical property)

contains to chemically distinct layers-the crust and upper mantle; it acts like a solid, rigid layer

asthenosphere (physical property)

weaker part of the mantle that s solid but relatively plastic; more viscous and can flow like "soft plastic" over long periods because of increased heat

mesosphere (physical property)

contains part of the mantle that behaves like a solid, "stiff plastic"; boundary btwn mesospere and outer core is a physical and chemical boundary

outer core (physical property)

part of the core that is a liquid

inner core (physical property)

part of the core that is a solid

age of the earth

4.5 billion years old

Bishop James Ussher

calculated the age of the earth by adding up several generations in the Bible; his creation date: Oct. 23, 4004 BC

Lord Kelvin

19th century; his creation date: earth approx. 24-400 million years old; neglected to account for radioactive decay

how is the earth's age calculated?

by determine the age of rocks by measuring the amt of radioactive decay since the rock was crystallized

seismic waves

the earth's energy that is released from a rupture in the earth; 3 kinds

p-waves

push/pull pulses of compression and extension in the direction the wave is traveling; behave like sound waves and will travel through solids, liquids, or gases; travel fastest

s-waves

move up/down perpendicular to the direction that the wave is traveling; can't travel through liquids or air; 2nd fastest

surface waves

travel near the Earth's surface and around it, not through it; slowest waves

seismograph

produces a record of ground vibrations called a seismogram

Snell's Law

when waves are passing through materials with different physical properties the waves will change velocity and bend (refract)

Mohorovicic Discontinuity

discovered by Andrija Mohorovicic(Moho); it marks the boundry between the Earth's crust and mantle which was discovered by studying seismic waves; it effects how waves move in the earth

mode conversion

when a wave is reflected back as multiple types of waves

seismic tomography

map of the earth's interior based in wave movement

Beno Gutenburg

determined the depth of the core-mantle boundary

Inge Lehmann

recognized that the composition of the inner core (a solid) differs from that of the outer core (a liquid)...discovered the inner core

ductile

when materials are subject to too much stress; deform by flowing and not return to original shape

brittle

materials are subject to too much stress; will break and become permanently deformed from original shape

isostacy

gravitational equilibrium

faults

rock surfaces that have broken in response to force

joint

breakage in a rock, but no relative movement has occurred

elastic rebound

on either side of the fault, force accumulate and start to cause increasing amounts of strain

slip

the amount of relative movement that happens on either side of a fault during a rupture

rupture area

the entire area that slipped during an earthquake

fault surface

the plane across which the fault occurs, including both rupture area and the part of the fault which did not rupture

hypocenter

the point at which the earthquake and rock failure begins

epicenter

the location on the earth's surface directly above the hypocenter

stress

= force/area + the direction from which stress is applied

vertical stress

applied from above and below; can make a rock shatter at a 45 degree angle

stress paradox

previous breakage=very little stress is needed to break the rock again

seismogenic zone

zone where earthquakes are more likely to occur; its thickness varies

geotherm

increase in temperature with increasing depth which weakens the rock making it more ductile

what increases the strength of the rock?

increase in pressure

what decreases the strength of the rock?

an increase in temoerature

theory of plate tectonics

the rigid lithosphere on the Earth's surface is divided into several pieces or plates that sit on the denser, plastic asthenosphere

isostatic equilibrium

the asthenosphere will flow away from an area where the lithosphere is thicker to counterbalance the added mass; balace btwn the two spheres

which crust is denser?

oceanic crust

Alfred Wegener

in the early 1900s, he proposed the theory of continental drift

magnetic strips

give evidence of seafloor spreading; gives a record of when earth's magnetic orientation changed, generated by the outer core; currently in a positive magnetic orientation

mid-ocean ridges

topographically high ridges or underwater mountain ranges; i.e. the mid-Atlantic ridge

curie temperature

the temperature at which the rock cools and leaves a lasting record of the Earth's magnetic orientation

divergent plate margins

occurs where two plates are moving away from each other where lithosphere is being created; hot material rises out of the mantle through a rift; aka accretionary margins

convergent plate margins

where plates collide and move closer together

lithospheric subduction

process where the oceanic plate sinks down because it is cooler and therefore denser than the mantle; a type of convergence

Wadati-Benioff Zone

the zone where earthquakes earthquakes are concentrated and can occur

transform plate margins

occur where two plates slide past each other; it can connect faults, convergent or divergent plate margins and is a place where lithosphere id neither created nor destroyed

San Andreas fault

example of a transform plate boundary and a right lateral strike-slip fault with a triple junction in northern California

Charles Richter

devised the Richter scale in the 1930s to quantify the earth's magnitude; it uses whole numbers and is logarithmic

convection

process by which material is heated becomes less dense, and then rises away from the heat source; it modifies the plates but does not create or destroy them

approx population of the earth

7 billion

what are significant contributors to the increase in economic loss due to natural hazards over time?

population growth, increase in concentration of people into urban areas, increasing complexity of infrastructure

where do the largest earthquakes occur?

around the pacific rim

where is continental crust formed?

at convergent plate boundaries

characteristics of basin and range province?

distributed deformation resulting from shearing along the san andreas plate boundary; numerous large earthquakes in the last 2 centuries; north-south oriented mountains and intervening valleys

why do great earthquakes occur primarily at convergent plate boundaries?

the dipping geometry of subduction zones keeps large rupture area above ductile conditions

volcanic spine

a block of solidified lava that grows and rises vertically from the volcano's dome

Krakatoa

island arc of Sumatra; created a tsunami

Mt. Pele

volcano in Martinique; located on a subduction plate which produces explosive/deadly volcanoes

Mt. St. Helens

1980 explosion; lateral blast; pyroclastic flow; lahar

Lake Nyos

in Cameroon; volcanic gas asphyxiation; carbon dioxide remained dissolved in the water until something (possibly an earthquake) shook the lake

vog

volcanic fog made up of poisonous gases

Mt. Vesuvius

79AD eruption buried Pompeii and Herculaneum

Yellowstone caldera

potential for massive present-day eruption

Heimay

volcano in Iceland erupted in 1973 created large a'a lava flows

sag pond

a topographic depression in the earth caused by the motion of a strike-slip fault; as the earth moves sediment material washes into the depression and is deposited

seismic gap

and area along the fault where earthquakes have not happened recently but have happened in adjacent locations

blind faults

these are buried faults that cannot be detected on the surface; the Northridge earthquake in 1994 occurred on one

Fort Conception earthquake

largest earthquake recorded in Chile in 1960 with a magnitude of 9.4

1964 Alaska Earthquake

magnitude 9.2; good Friday earthquake

Mexico City 1985

San Fernando Earthquake in western mexico on a subduction plate; built on a swamp

wavelength

the distance between two successive wave peaks or troughs in ocean waves

wave period

the length of time that it takes for a complete wavelength to pass through a location

bathymetry

refers to the depth and contours of the ocean floor

delta

when sediment builds up from lack of kinetic energy at a river bottom

meanders

a bend in the river created by an obstacle like rock in the river

floodplain

when water overflows from the river and dumps river sediment on the surrounding land

quicksand

sand-saturated water layer formed when water is under high pressure in an area of unconsolidated, loose sediment

slumps

a type of landslide that occurs when forces acting on a pile of earth build up to a point where internal cohesion fails and the ground is pulled downslope

subsidence

when the ground compresses ad sinks beacuse liquids like oil or water have been removed from under it

sinkholes

circular depressions in the ground where the ground has fallen in; they commonly form in areas where acidic groundwater eats away at bedrock composed mainly of calcium carbonate

asteroids

larger rocky and metallic subplanetary masses in space

comets

made up of ice and dirt; when they travel close to the sun the ice melts and debris is blown away creating a trail

sites of past meteor impacts

Chesapeake Bay; Meteor Crater in Arizona; Sudbury, Canada (positive effects); Chixculub area in the Gulf of Mexico

torino scale

it categorizes the likelihood of an impact and the damage it would cause

potential deadly extraterrestrial hazards

coronal mass ejections, supernovas, black hole, gamma ray burst, extraterrestrial microbes, the death of the sun

tornado

narrow column of intense winds that passes over land and water created by a collision of air masses with different temperatures and levels of moisture; 330 feet with wind 224mph

dust devils

very small vortices; 3.3 feet in diameter and up to 22mph; very weak winds that move vertically

waterspouts

vortices that occur over water; 33 feet in diameter and up to 112mph ; formed by small thunderstorm that first is on land then water, can form from hurricanes, in the great lakes

cold fronts

places where tornadoes are usually formed when cold, sinking masses of air move with warm, moist air forcing warmer air into the atmosphere

mammatus clouds

look like a mass of cotton balls

stages of tornado formation

1. organization
2. mature stage
3. shrinking stage
4. rope stage

Fujita scale

used to rank the intensity of a tornado and is based on surveys about the amount of damage that a tornado has caused to an area's structures and vegetation

aerosol

a piece of solid particulate matter that is suspended in the atmosphere i.e. carbons (soot) and sulfates; have a cooling effect on the earth's temp.

radiative forcing

an imbalance between the amounts of radiation coming in and out of the Earth system that causes the Earth's radiation budget to diverge from its natural state of equilibrium; caused by an increase of carbon dioxide and greenhouse gases

positive feedback

where changes to one part of a system produce effects that amplify that change even further

1st stage in hurricane development

an appearance of a cluster of thunderstorms over the tropical oceans known as a tropical disturbance

2nd stage in hurricane development

tropical depression-when the sustained wind speeds of the storm system reach 23 mph

3rd stage in hurricane development

tropical storm-wind speeds rise to 39 mph and receives a name

4th stage in hurricane development

the storm is classified as a hurricane-wind speeds reach 74 mph

cloud shield

500-600 kilometers in diameter cloud that rotates around the center known as the eye

eyewall

outside the eye, a ring of intense thunderstorms and rain with very strong winds

coriolis forces

act on the moving air masses, causing them to spiral together

conditions for hurricane formation

1. warm sea surface temp above 79 degrees Fahrenheit
2. considerable moisture available at lower levels of the Earth's atmosphere
3. light winds throughout troposphere
4. needs to be a convergence of air masses with different pressures and temperatures to trigger the storm

Saffir-Simpson scale

used to rank hurricanes in terms of their intensity and therefore the potential damage they can cause

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