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Earthquakes and Volcanoes

Terms in this set (57)

Earthquake
Vibrations of the Earth when rocks break.
Liquefaction
The phenomenon that occurs when the shaking motion of an earthquake causes water-saturated sediments to temporarily lose strength and act as if it were a liquid.
Batholith
Large intrusive igneous body that forms when magma cools beneath the surface.
Seismic Wave
Energy in the form of a wave that travels away from a seismic(earthquake) source.
Pyroclastic Flow
An avalanche of gas, ash, and rock flowing down the side of a volcano; common in subduction zones and hot spots.
Epicenter
The location on Earth's surface that is directly above the focus of an Earthquake.
Seismograph
An instrument used to detect waves that transfer an Earthquakes energy.
Caldera
Huge, roughly circular crater left after a volcanic explosion or collapse of a volcanic cone.
Dike
An igneous intrusion that has cut vertically or at an angle across layers of pre-existing rock.
Hot Spot
the result of an unusually hot area at the boundary between Earth's mantle and core that rise as currents or plumes melting rock under the crust and erupting as lava.
Volcano
Any opening in Earth's crust where hot molten rock ashes, gases, and rock fragments erupt.
Seismogram
Seismographs worked by graphing the p,s, and surface waves generated by an earthquake to produce drawings.
Asthenosphere
Part of the mantle below lithosphere.
Focus
Point where earthquakes originate.
Effusive Eruptions
type of volcanic eruption; produce mainly lava flows, yield low-viscosity basaltic lavas.
Magnitude
The measure of an earthquakes relative size; depends on the type of seismograph used.
Lahar
Flowing ash and water(mudslides); consistency of wet cement.
What does the viscosity of magma depends upon?
pressure, amount of dissolved gases, and chemical composition
What type of an eruption is produced with magma high in silica?
explosive eruptions
What is the difference between Pahoehoe and aa' lava?
pahoehoe lava is basaltic lava that has a smooth, ropy appearance and "aa" lava is a jagged, stony, rough, lava.
What are the Hawaiian Islands and the Yellowstone caldera examples of?
Hot spots
What type of rock would you expect to form as a result of an explosive eruption?
Granite, Andesite, Rhyolite.
What provides the force that causes magma to erupt to the surface?
the buoyancy of the magma, the pressure from exsolved gases and a new batch of magma injected to an already filled magma chamber
What can be used to identify a substance or to predict how it will behave?
physical and chemical properties
What triggers the small earthquakes that occur around a volcano before an eruption?
the fluid pressure from the rising magma cracks the rocks, the tectonic plates under the Earth's crust are moved and as a result earthquakes are caused.
What is the main hazard from a quiet eruption?
The lava flow can produce poisonous gases.
What are the vibrations in the earth caused by the sudden movement of rock called?
earthquake
What is a characteristic of an earthquake that causes the most severe damage?
Tsunami.
Where do most severe earthquakes occur?
California
What do P waves travel through?
Travel through both solids and liquids
What can scientists determine by analyzing the difference in the time it takes for P-waves and S-waves to arrive at a seismograph?
distance from there to the epicenter
What does the Richter scale measure?
magnitude of an earthquake
What causes damage days or weeks after a major earthquake?
aftershocks
In what direction do seismic waves carry the energy of an earthquake?
all directions away from the source
What type of stress pushes a mass of rock in opposite directions?
shear
What does a seismograph record?
they detect waves that transfer an Earthquake's energy.
What type of seismic wave cannot travel through liquids?
Surface Waves
What is used to measure magnitude?
Richter scale
what is a graph of seismic wave called?
Seismograph
What are the Richter Scale and the Moment-magnitude Scale based on?
the Richter scale is based on ground motion and the moment-magnitude scale is based on the area of the fault that ruptures.
What does the Modified Mercalli Scale measure?
used for measuring the intensity of shaking produced by an earthquake.
What are the consequences of earthquakes?
Tsunamis and liquefaction
What are the factors for liquefaction to occur?
you need waterlogged sediments and the shaking of the ground from an earthquake
What layer of the Earth is very thin and brittle compared to what is below it?
lithosphere
What is the layers beneath the crust but above the outer core called?
Mantle
What is the layer called that is composed of iron and nickel and is completely solid?
Core
What layer is weak, has the consistency of silly putty, on which the lithospheric plates "float" upon?
Asthenosphere
What type of volcano is Kilauea, Hawaii?
Shield volcano
What type of boundary is associated with the composite volcanoes?
Convergent Boundary
How are magma formations on the surface revealed?
stored gas
What do high silica content magmas produce?
light-colored granitic rocks
What do low silica content magmas produce?
dark-colored basaltic rocks
How does the release of trapped gases in magma cause a volcano to erupt?
It causes the lava to rush out faster.
How is the moment magnitude scale used to describe earthquakes?
First the seismic moment is computed, and then it is converted to a magnitude designed to be roughly equal to the Richter Scale in the magnitude range where they overlap.
Explain how you would find the epicenter of an earthquake. Be detailed and exact.
The distance between the beginning of the first p-wave and the first s-wave tells you how many seconds the waves are apart. This number will be used to tell you how far your seismograph is from the epicenter.
How are volcanoes and earthquakes similar?
Most earthquakes are along the edges of tectonic plates. That is where most volcanoes are too, but most earthquakes are caused by the interaction of the plates not the movement of magma .
Why does liquid magma flows upward through cracks in rocks?
Magma rises through cracks from beneath and across the crust because it is less dense than the surrounding rock. When the magma cannot find a path upwards it pools into a magma chamber.
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