active volcano

volcanoes that have erupted within historic times

andesitic magma

contains about 60 percent of SiO2 and a lot of dissolved gas

basaltic magma

80 percent of all magma erupted from volcanoes; 50 percent SiCO2 amd little dissolved gas

body wave

travel outwards in all directions from the focus and have the capacity to travel through Earth's interior
-p-waves and s-waves

caldera

many large volcanos, especially shield and stratovolcanoes are marked their summit by a large depression. the depression is circular, steep-walked basin of several kilometers or more in diameter. form after partial emptying of a magma chamber in an explosive volcanic eruption

deformation

a change in shape or size of body

elastic energy

the energy used to bend something doesn't disappear, instead it's stored in the object. when bending force is removed, it's this energy that reshapes the object to original size
-can be converted to heat, soundwaves, and vibration

elastic rebound hypothesis

hypothesis for how energy is spread during earthquakes, as rocks on opposite sides of a fault are subjected to force and shift, they accumulate energy and slowly deform until their internal strength is exceeded.
San Andreas Fault (fence picture)

epicenter

the point on earth's surface that lies vertically above the focus; the location can be determined from the arrival times of seismic body waves on seismograph

fault

a fracture or zone of fractures [in earth's crust] along which there has been [movement] of the sides relative to one another; when slippage of rocks occur along a break or fracture in a rock

fissure eruption

sometimes lava reaches the Earth's surface through a vent that is an elongate fracture in the crust. these eruptions can be dramatic and are associated with fluid basaltic magma and the lava spreads so widely and creates flat lava plains

focus

the point where energy is first released during an earthquake and from which the seismic waves travel outward; may not be a simple point, can be a region that extends along the fault plane

hot spot

locations where lava is fed to the surface by upwelling masses of hot material called plumes

lava

magma that reaches earth's surface

liquefaction

sudden disturbance of water-saturated sediment and soil can turn solid ground to liquid-like mass of quicksand and was one of the major causes of damage during the Anchorage, Alaskan earthquake and the Niigata, Japan earthquake

magma

the mixture of molten rock, suspended mineral grains and dissolved gas that forms in crust or mantle

magnitude

the calculation of the amount of energy released during an earthquake

moho

boundary between the crust and mantle; the depth where seismic waves change velocity and chemical composition

p-wave

first wave to be recorded by seismograph, can travel through water, faster; caused body changes in rock (compression, expansion)
-can pass thru gases, liquid and solids

plume superplume

upwelling masses of hot material

pyroclast

fragment of hot, shattered magma or any other fragment of rock ejected during an explosive volcanic eruption

rhyolithic magma

contains about 70 percent of SiO2 and highest gas content

s-wave

second wave to reach seismograph; can transverse through Earth's interior, slower; shear waves perpendicular to the direction of the wave travel , don't travel thru liquids and gases and don't have shapes

seismicity

earthquake activity

seismograph

many continuous recording devices that can detect seismic waves

shield volcano

a broad, roughly dome-shaped mound, built up of successive flows of very fluid lava capable of flowing great distances ; characteristically formed by successive eruptions of basaltic lava
Hawaii, Tahiti, Samoa, Galapagos have many of them

stratovolcano

steep conical mountains that consist of layers of both lava and tephra and their slopes can be thousands of meters high and like those of tephra cones
Mount Fuji, Mount Rainier, Mount Baker, Mount Hood

surface wave

travel around Earth rather than through it, are guided by earth's surface, are slow but huge and have long wavelengths; greater amplitude= greater damage

tephra

deposit of unconsolidated (loose) pyroclasts

tephra cone

a steep-sided volcano that builds around the vent; created when rhyolitic and andesitic volcanoes eject large proportions of pyroclast. the slope is determined by the size of the pyroclasts

tsunami

seismic sea wave, often euphoniously called tidal waves but has nothing to do with tides, sudden movement of the seafloor caused by an earthquake, volcanic eruption, or underwater landslide particularly destructive in the Pacific and Indian oceans

viscosity

property that causes a substance to resist flowing, the more viscous a magma, the less fluid it is, magma's viscosity depends on temperance and composition especially the SiCO2 content

volcanic ash

the smallest tephra particles

volcanic gas

small amounts of gas are dissolved in all magmas and they play a big role in eruptive process , the principal is water vapor

volcano

a vent from which combination of melted rock, solid rock debris and gas is erupted

earthquake primary effects

ground motion, surface rupture

earthquake secondary effects

fires, landslides, liquefaction, tsunami

spreading ridge seismic activity

shallow earthquakes with low maginitude

transform fault seismic activity

shallow focus but sometimes powerful earthquakes

continental collision seismic activity

shallow-deep focus , can be powerful

subduction zones seismic activity

deepest and most powerful earthquakes, can cause tsunamis

megathrust earthquake

where subducting plate is being overridden by another plate

earthquakes

occur when rock masses break and slip past one another along a fault, allow scientists to obtain info on Earth's interior