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118 terms

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