1st natural disasters test

decompression melting

melting that occurs when pressure decreases but temperature remains unchanged, occurs in the earth where hot mantle rock rises to shallow depths and partially melts as it decreases in pressure, allowing magma formation.

volatile

an element or compound that can melt at relatively low temps & can exist in gaseous forms at the earth’s surface

flux melting

the transformation from hot solid to liquid that occurs when volatile material is added to the solid occurs where volatiles released from the downgoing slab enter the overlying asthenosphere

heat transfer melting

melting that results from the transfer of heat from a hotter magma to a cooler rock with a lower melting temp

what does the specific composition of a melt/magma depend on?

source-rock composition, partial melting, fractional crystallization, & assimilation of wall rock

viscosity

the resistance of material to flow

magma chamber

where rising magma accumulates, it can sometimes solidify, or it will continue to rise

felsic magma

high silica composition, low melting temp, high viscosity

mafic lava

lower silica composition, very high melting temp, lower viscosity

intrusive igneous rock

rock formed by the freezing of magma underground

plutons

blob-shaped intrusions

dikes

wall-shaped intrusions formed where magma solidifies in large cracks

sills

tabletop-shaped intrusions formed where magma squeezes between pre-existing layers

extrusive igneous rock

rock that forms when lava freezes after it extrudes onto the earth’s surface & comes into contact with the atmosphere or ocean

lava flows

masses of lava that flow onto the earth’s surface

pyroclastic debris

ash & other fragments blasted out of a volcano

melt that solidifies quickly yields a

glassy texture

melt that solidifies more slowly yields a

crystalline texture

rocks with fragmental texture are made from

pyroclastic debris

where can igneous activity occur?

divergent boundaries, convergent boundaries, hot spots, & continental rifts

where do volcanic eruptions at mid-ocean ridges take place

open vertical cracks (fissures) parallel to the ridge axis

black smoker

a hydrothermal vent along a mid-ocean ridge that spews hot, mineral-rich water, whose dissolved sulfide components instantly precipitate when the water mixes with seawater & cools to produce a dark cloud of tiny mineral particles

where do most subaerial volcanoes occur?

convergent boundaries

ring of fire

an informal term for the belt of convergent boundaries along the margin of the pacific ocean

volcanic arc

a chain of active volcanoes formed adjacent to a convergent boundary

flood basalt

a huge volume of low-viscosity mafic lava that erupts over a relatively short time & spreads in a layer of a large area

large igneous province (LIP)

a region of extremely voluminous volcanism that can produce abundant flood basalts or immense quantities of ash

lava dome

a dome-like mass of rhyolitic lava that accumulates above a volcanic vent

lava tube

the empty space left when a lava tunnel drains; occurs when the surface of a lava flow solidifies while the inner part of the flow continues to stream downslope

lava lake

a pool of lava tens to hundreds of meters deep that has collected around a volcanic vent

lava fountain

an eruption of lava that is under pressure, during which the lava spurts as high as a few hundred meters

pāhoehoe

a lava flow with a surface texture of smooth, glassy, rope-like ridges

‘a‘ā

a basalt lava flow with a rubbly surface

tephra

unconsolidated accumulations of pyroclastic material

ash

very fine particles of glass or pulverized rock erupted by a volcano

lapilli

marble-to golf ball-sized pyroclastic particles consisting of frozen lava clots, fragments of pre-existing rock, or ash clumps

cinder

lapilli formed from solidified clots ejected by a lava fountain

block

a large, angular chunk of pyroclastic debris

volcanic bomb

a large piece of pyroclastic debris that is still soft when erupted & attains a streamlined shape during eruption

volcanic edifice

a hill or mountain composed of solidified lava and/or pyroclastic debris that builds up around a volcanic vent

crater

a bowl-shaped depression at the peak of a volcano

shield volcano

a subaerial volcanic edifice with the shape of a broad, gentle dome; it forms many successive layers of low viscosity mafic lava, & contains relatively little pyroclastic debris

caldera

a large circular/elliptical depression with steep walls & a fairly flat flow, formed after a volcanic eruption as the summit of the volcano collapses into the drained magma chamber below and/or gets blasted away during an explosive eruption; large ones form after large volcanic explosions

strato/composite volcano

a large, cone-shaped subaerial volcanic edifice consisting of alternating layers of lave & pyroclastic debris

effusive eruption

a volcanic eruption that produces mainly lava

explosive eruption

a violent volcanic eruption that produces clouds & avalanches of pyroclastic debris

phreatomagmatic eruption

an explosive volcanic eruption that results from the outward pressure that develops when magma heats water to form water vapor that expands & blasts out lava & pyroclastic debris

phreatic eruption

an explosive volcanic eruption resulting from the outwards pressure that develops when heat from magma rapidly transforms liquid water into water vapor that expands & blasts out pyroclastic debris, but not lava

eruptive jet

material, composed of hot pyroclastic debris & some lava, driven skyward up to several hundred meters during an explosive volcanic eruption

pyroclastic flow

a fast-moving, intensely hot avalanche that occurs when scalding volcanic ash, gas, & debris mix with air & flow down the side of an erupting volcano

ignimbrite/ash-flow tuff

igneous rock formed from a pyroclastic flow that comes to rest, compacts, & undergoes lithification

volcanic explosivity index (VEI)

a logarithmic scale used to classify explosive volcanic eruptions by size, based on the volume of erupted tephra as measured in cubic kilometers

super volcano

a volcano that ejects more than 1,000 km³

eruptive style

the specific manner in which material comes out of a volcano in a particular volcanic eruption

hawaiian eruptions

predominantly effusive & produce mafic lava flows that build over time into shield volcanoes; usually produce phreatic explosions

surtseyan eruptions

substantial phreatomagmatic eruptions driven by the interaction of magma with water; causes the development of explosive pressure that can blast material out of the volcano is clouds of debris & steam, forming jagged fragments of glassy volcanic rock

strombolian eruptions

eject burst-like lava fountains & eruptive jets of scoria bombs, lapilli, & some ash; more explosive than hawaiian eruptions because its magma is more viscous, so gas bubbles can’t escape from it as easily, instead coalescing into large bubbles; relatively low VEI

vulcanian eruptions

similar to strombolian eruptions, but the lava’s viscosity is higher; eruptions produce lots of ash

peléan eruption

characterized by pyroclastic flows

plinian eruption

huge explosive eruptions with a relatively long-lasting eruptive jet & a huge connective cloud

why is mafic lava from effusive eruptions such a big threat?

it can flow relatively quickly & spread over a broad area

lahar

a slurry composed of volcanic ash & debris mixed with water, flowing either down river channels or down the flank of a volcano; more dense than water so it is more dangerous as it can carry away nearly everything in its path

vog

air pollution formed when sulfur-bearing volcanic gases react with atmospheric water to produce acidic aerosols, which are then trapped near the ground by an inversion

laze

an atmospheric hazard caused when lava entering seawater produces a could of steam containing hydrochloric acid as well as fine particles of ash

fumarole

a vent at an active volcano that emits volcanic gases & steam

volcanic unrest may be shown by changes in what?

seismicity, changes in heat flow, increases in gases, changes in shape, groundwater changes, computer models of volcanic systems, movement of lava, & infrasound emissions

earthquake

an episode of ground shaking caused by the sudden breaking of rock, or by a frictional sliding along a preexisting fault in the earth

tsunami

a wave produced by the sudden movement of a mass against water

rockfall

mass wasting that involves the sudden drop of a mass of rock from a vertical cliff or overhang, so that for part of its downward journey, the rock free-falls through air

landslide

an informal term for sudden movement of rock & debris down a slope

volcanic eruption

an event during which lava and/or pyroclastic debris is expelled from a volcanic vent

lava

molten rock that has flowed out onto the earth’s surface

storm

an episode of strong wind & heavy precipitation, sometimes accompanied by lightning

thunderstorm

a cumulonimbus cloud that produces lightning & thunder

tornado

a nearly vertical, funnel-shaped cloud in which air rotates violently, occur in association with the updrafts of strong thunderstorms; as they move along the ground, they leave a track of destruction

hurricane

a strong tropical cyclone over the north atlantic or eastern pacific ocean, in which sustained wind speeds reach or exceed 119 km/hr (74mph)

flood

an event during which water covers significant areas of land that are normally dry

when does a stream flood

when its discharge becomes so great that the water over tops the stream’s banks & submerges areas outside its channel

drought

an extended period of little or no rain that causes a deficiency of freshwater

heat wave

a prolonged period of abnormally high air temps

wildfire

an uncontrolled, self-sustaining blaze sweeping across the landscape that may consume forests, grasslands & neighboring communities

solar storms

an explosion-like event in which the sun ejects particularly large amounts of high-energy particles into space; this can result in a disturbance of the earth’s magnetic field called a geomagnetic storm

meteorite impact

the point of collision of an object from space with the earth

anthropogenic hazard

a hazard produced by the activities of people (explosives, insecticides, smoking, & drug use)

natural hazard

a phenomenon/process that exists independently of human activity, that nevertheless has potential to harm people/property and therefore represents a threat to society

natural hazardous event

a disturbance caused by a natural hazard that damages & destroys features on a portion of the earth’s surface, disrupts the environment, & may cause human casualties & destruction of property

natural disaster

a natural hazardous event that causes many human casualties, extensive property destruction, & economic loss so significant that victims need outside help & resources to survive and recover

socio-natural disasters

both anthropogenic and natural

the earth system

the geosphere, hydrosphere, atmosphere, & biosphere, along with the intricate ways in which these realms interact with one another over time

pandemic

the spread of a disease over many countries, so that it affects a large part of the world & vast numbers of people

rapid-onset disaster

a natural disaster that begins so quickly that people do not have time to evacuate or take precautions (ex. earthquake)

slow-onset disaster

a natural disaster that takes days or weeks to develop, providing people with time to prepare (ex. flood)

stealth/creeping disaster

a disaster that takes so long to develop that its onset may not be noticed for months to decades (ex. sea level rise, drought, groundwater depletion & soil erosion)

groundwater

water that resides under the surface of the earth, mostly in pores or cracks in rock or sediment

chronic health disaster

a type of disaster caused by widespread, continuous use of materials, such as contaminated water, that are dangerous to human health

primary disaster

the casualties & destruction that result directly from a natural hazardous event (ex. buildings collapsed by an earthquake & homes destroyed by a flood)

secondary disaster

a hazardous event triggered by, & following, a primary disaster (ex. firestorm after earthquake)

tertiary disaster

a disaster that follows a secondary disaster (ex. earthquake makes water supplies toxic, which triggers a disease outbreak)

modified mercalli intensity scale

used to classify earthquakes by the damage sustained and the perception of ground shaking

moment magnitude scale

used to classify earthquakes by the amount of energy an earthquake releases