Natural Hazards

Events that overwhelm regions, international assistance is needed, require major reconstruction

Human loss- impacts of death toll, types of disaster, location, population density, structural loss, economic damage, displacement.

Insurance claims- delayed real cost, higher GDP (gross domestic product) may result in safer buildings

• democratic index
• -thousands died in Hurricans (most deaths), typhones, EQ, and terrorist attcks

• Gross domestic impact
• -millions of dollars lost in natural disaster

• Social environment
• -socio economic characteristics
• - knowledge of an environment or type of event
• - ability to cope
• - geting help

• Political environment
• Economic environment

Risk: likelihood something will happen, and consequences if it does happen


Vulnerability: susceptibility to harm of those at risk, depend on characteristics of a person or group

• actions taken by humans to minimize the possible effects of a natural hazard
• - action plans prior to and after an event

exponential

• number of years required to double the population given an annual percentage
• - growth about 1.2%

• high birth rates- grows 80,000,000 ppl every year
• better housing/technology
• advances in the medical world

• demographic transition theory
• mortality and fertility rates decline
• population referenc bureau estimates world population growth rates are dropping (1.8% in 1990 to 1.2% in 2008)

• growth slws but population explosion continues
• avg. 1.6 children/woman: 3.6 bilion

• low birth rate- long life expectancy
• high birth rate- shorter life expectancy

• migration to urban areas
• mega-cities

• an ever changing #
• food?
• resources?

• poor soil
• 30 native plant species
• no mamals
• 25-50original olynesian settlers brought chickens, rats, and various plants

• Carrying capacity for Easter Island
• reached by dutch ship in 1722
• easter sunday

• Core: iron and nikel
• mantle: composed of mostly solid rock
• crust: floats on top of mantle

• part of earths lithosphere that surfaces in the ocean basin
• about 5-10km thick
• basalt

Layers of igneous sediment & metamorphic rocks which froms the continents and the areas of shallow seabed close to shores (continental shelves)

Less dense materials float on top of more dense materials (iceberg floating in ocean)

• Stresses:
• brittle- faulting
• elastic-folding

suggest that the earths crust is composed of several tectonic plates that have the ability to move around

landmass comprising more than one continental core, or craton

• supercontinent
• used to unite all the continents
• continents seem to fit together
• plant & animal fossil record across continents
• geologic deposits similar on different continents

• rigid outermost shell of a rocky planet
• broken into plates separated by divergent zones, transform faults, and convergence zones

the grand recycling of the upper few hundred kilometers of earth

• tensional stress
• non-explosive (found on hot spot)
• linear deature that exists between two tectonic plates that are moving away from each other
• produce rifts which produc rift valleys
• most active occur between oceanic plates (exist as mid-oceanic ridges)

• compression stress
• Largest earthquakes- 2 or more collide causing EQ and volcanoes
• Oceanic plate vs oceanic plate
• Oceanic plate vs continental plate
• Continental plate vs continental plate
• Subduction zones: Large earthquakes, at shallow depths Compressive movement Pull-a-part where the plate is shifting downward At deeper point- Less severe earthquakes
• Seismic gap: Look for breaks in earthquake centerso Not a science one location could see two earthquakes before a gap may see one

• Sheer stress
• relative motion is horizontal

• releases stress along a fault line
• EQ commonly caused by volcanic activity
• magma moving
• undersea landslides

point on the surface directly above a fault movement

initial portion of a fault that moved to generate the ground- below the surface

the scientific study of earthquakes and the propagation of elastic waves through the Earth or through other planet-like bodies.

must have a part that remains stationary and a part on the ground that will vibrate

• Amplitude
• Wavelength
• Period
• Frequency
• Hertz

Can occur through the entire depth- surface to core

• Primary waves: Fastest of the waves, Marked by compression and expansion, Travel through earth, water, and gas
• push pull movement

• Secondary waves: Slower, Transverse in motion, Travel only through solids
• Movement similar to a jump rope

• Only occur on the surface
• Love waves: Similarly to S waves, but side to side
• Do not move through water
• Rayleigh waves: Backwards elliptical motion- rolling waves
• Slowest
• More energy released when the focus is close to the surface

• Waves can move through the earth (towards the core)
• Do not move in straight lines
• Waves speed up until reaching the asthenosphere
• Slow initially in the mantle but then speed up

• Based on the time difference between the arrival of primary and secondary waves
• P-s then down to the distance
• Not directional though

• Magnitude
• Righter scale: measure it on
• Richter does not work well for distant or large earthquakes
• Can both under and overestimate the magnitude
• Commonly used
• In use since 1935
• Best for epicenters less than 300 mi from the seismometers
• Based on the idea the bigger the quake the greater the shaking

• Moment magnitude scale: Seismic moment- moving on the whole line
• Uses seismic moment: Mw = 2/3 log10 (Mo) – 6

• Mercalli: Describes the intensity felt by people
• Used to help define magnitudes of historical events Mercalli variables:
• Magnitude
• Distance from epicenter
• Foundation materials
• Building style
• Duration of the shaking

• Eliminate resonance
• Change height of building
• Move weight to lower floors
• Change shape of building
• Change building materials
• Change attachment of building to foundation
• Hard foundation (high-frequency vibrations)
• build tall, flexible building
• Soft foundation (low-frequency vibrations)
• build short, stiff building
• sheer walls- Brased frames
• retrofitting: Base isolation

• Foreshocks: smaller quakes that happen prior to the main shock
• Mainshock: much larger, can get reclassified if the aftershock is larger than the main shock
• Aftershock: smaller earthquake that occurs after a previous large earthquake, in the same area of the main shock. If an aftershock is larger than the main shock, the aftershock is redesignated as the main shock and the original main shock is redesignated as a foreshock.

• Major quakes
• Turkey
• California

• Giant, long-period sea waves caused by oceanic disturbances·
• Japanese word (no plural)·
• Not giant cresting wave·
• Characteristics: Most commonly occur after earthquake, Water is not compressible, Water retreat, Many waves

• Leading edge of an elevated mass of water
• High velocitiy
• Reaching the shore: When they reach the shore the front slows and the water behind builds up increasing amplitude·
• Destruction: Not because of the height of the wave but the momentum and multiple waves or how many there areo Can stay on shore about 30 min then pull back
• Long wave lengths help the waves bend around islands and hit all sides of the island

• Must have vertical plate movement
• Magnitude of at least 7.5
• Examples: Alaska- 2 large subduction EQ’s, Chile- strongest EQ at 9.5

• Usually from explosions and collapses
• Example: Krakatau, Indonesia 1883

• Gravity pulling rock and sediment masses into the ocean
• Subocean
• Example: Canary islands, Volcanic collapse, 3 mega collapses, Lake and bay tsunami @ 8.0 magnitude

• Network of earthquake detecting stations
• Thirty two pressure sensors that weigh the water passing over them

• what should we do:
• Get to higher ground
• Move inland
• Upper floor of a strong building
• Tree
• Anything that floats

• Japan: March 11, 2011
• 9.0 magnitude quake
• 500 km rupture off the northeast coast of Honshu
• Wave reached the mainland within minutes
• Inland as far as 6 miles with waves as high as 38m
• Death toll at 27,500
• Damage cost of 326,000,000,000

• 90% of volcanoes are associated with plate boundaries
• 80% occur at oceanic spreading zones
• 7-13% occur at subduction zones
• 10% occur at hot spots

Magma: mixture of molten or semi molten rock, volatiles and solids that is found beneath the surface of the Earth, and is expected to exist on other terrestrial planets.

Lava: Pahoehoe and aa , refers both to molten rock expelled by a volcano during an eruption and the resulting rock after solidification and cooling

• Active: Erupt regularly, Within the Holocene (12,000 years ago to present) ,1,500 worldwide, 50 in the United States
• Dormant: No written record, Most super volcanoes/calderas
• Many dormant volcanoes are misclassified
• General rule: if well shaped it should be considered active
• Extinct: Highly unlikely to erupt due to lack of lava source

• measure of the fluidity of a liquid
• Water vs. honey
• Temperature
• Silicon and oxygen
• Mineral and crystals

• Eight elements make up 98% of continental crust
• Oxygen and Silicon: differences in silicon dioxide percentages impact the type of eruptive behavior

Dissolved gases: water

• Hawaiian Commonly preceded by a swarm of earthquakes
• Fractures release gas out of the caldera allowing then for floods of basaltic lava to flow down the slopes
• Icelandic :Fissure eruptions
• Build volcanic plateaus that are flatter than a shield volcano
• Most peaceful eruptions

• Strombolian-type eruptions: Typical eruption for a scoria cone
• Large amounts of pyroclasts into the air

• Vulcanian: Named for the Roman god of fire and blacksmith
• Alternated between thick, highly viscous lavas and pyroclastic material blown out of the top
• Plinian: Named for the 17-year-old Pliny the Younger in honor of his detailed written observations of the 79 CE eruption of Vesuvius
• Gas powered vertical eruptions that carry pyroclastic material up to 50 km into the air

• Volcanic ash
• Tephra
• Rocks

• Submarine volcano in the Bay of Naples
• First eruption in 79 CE
• About 4,000 people died in Pompeii
• Volcano weather"
• Lahars

High-viscosity magma with a low volatile content cools quickly forming a plug over the top of the volcano vent

Large volcanic depressions formed by the collapse of the emptied magma reservoir

• Three in the United States:
• Valles
• Long Valley
• Yellowstone

• Circular depression in the ground caused by volcanic activity.
• It is typically a basin, circular in form within which occurs a vent (or vents) from which magma erupts as gases, lava, and ejecta

• Hotspot
• Three previous eruptions
• Caldera (in yellow stone) is 75km long and 45km wide Two resurgent domes,where we see proof of rising magma

• Shield volcanoes: Low viscosity, low volatiles and large volume ›Many thin volcanic rock layers
• Mauna Loa in Hawaii

• Stratovolcanoes (composite): Steep-sided, symmetrical peaks
• Marked differences in magma composition from eruption to eruption

• Scoria cones :Small conical hills
• Usually single eruptive
• Crater is usually less than 2 km in diameter

• Flod basalts: Largest volcanic events on Earth
• Measure about 1,200 mi by 1,200 mi and tens of meters thick