Term
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Definition
the shaking or trembling caused by a sudden release of energy in the earth
this release of energy is usually associated with a rocks slip along enormous cracks in the earth's crust |
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Definition
| the continuous adjustment of position of the earth's crust |
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Term
| what is the elastic rebound theory? |
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Definition
explains how energy is stored in rocks:
rocks can bend until the strength of the rock is exceeded >> rupture occurs and the rocks quickly rebound to an undeformed shape >> energy is released in waves that radiate outward from the fault (rupture) |
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Definition
| the point within the earth where faulting begins |
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Definition
| the point directly above the focus on the surface- where the surface breaks. |
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| how do we record earthquakes? |
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Definition
| seismographs record earthquake events |
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Definition
| at convergent boundaries, focal depth increases along a dipping seismic zone called a Benioff zone |
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| Where do earthquakes occur and how often? |
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Definition
| 80% of all earthquakes occur in the circum-pacific belt |
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| What are the economic and societal impacts of earthquakes? |
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Definition
| collapsing buildings, fires, tsunamis, ground failure |
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Term
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Definition
response of material (ground) to the arrival of energy released from a rupture site.
two types:
body waves >> P and S
surface waves >> R and L |
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Term
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Definition
| fastest waves; travel through solids, liquids or gases; compressional waves: material moving in the same direction as wave movement |
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| what are secondary waves? |
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Definition
| slower than P waves; travel through solids ONLY; shear waves: move material perpendicular to wave movement |
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Term
| what are rayleigh and love waves? |
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Definition
| travel just below or along the ground's surface; slower than body waves; rolling and side-to-side movement; esp. damaging to buildings |
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Term
| how is an earthquakes epicenter located? |
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Definition
seismic wave behavior
P waves arrive first, then S, then L and R; the average speeds of all of these waves is known; after an earthquake, the difference in arrival times at a seismograph station can be used to calculate the distance from the seismography to the epicenter
the farther away a seismograph is from the focus of an earthquake the longer the interval between the P and S waves
three seismograph stations are needed to locate the epicenter of an earthquake; a circle where the radius equals the distance to the epicenter is drawn; the intersection of the circles locates the epicenter |
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Term
| how are the size and strength of an earthquake measured? |
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Definition
mercalli intensity scale- subjective measure of damage done and peoples reactions to it, isoseismal lines identify areas of equal intensity
richter scale measures the magnitude (total amount of energy released by an earthquake) |
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| what are the destructive effects of earthquakes? |
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Definition
| ground shaking- amplitude, duration and damage increases in poorly consolidated rocks. |
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Term
| can earthquakes be predicted? |
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Definition
earthquake precursors- changes in elevation or tilting of land surface, fluctuations in groundwater levels, magnetic field and electrical resistance of the ground
earthquake prediction programs- include the laboratory and field studies of rocks before, during and after earthquakes; monitor activity along major faults; produce risk assessments |
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Term
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Definition
a volcano is a weak spot in teh crust where molten material or magma comes to the surface
the magma that reaches the surface is called lava |
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Term
| where are volcanoes located? |
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Definition
there are 600 active volcanoes worldwide.
there are many more that are found beneath the oceans.
most volcanoes occur in belts that extend across continents or oceans.
the major belt encircles the pacific ocean and is called "the ring of fire."
most volcanoes occur at divergent plate boundaries such as the mid-ocean ridge, or in subduction zones around the edges of oceans. |
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Term
| what are hotspot volcanoes |
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Definition
form where magma from deep within the mantle melts through the crust like a blow torch
examples: hawaiian islands, yellowstone national park |
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Term
| what happens inside a volcano/what are the parts? |
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Definition
| all volcanoes have a pocket of magma beneath the surface and one or more cracks through which magma forces its way through. this magma pocket is called the magma chamber. a pipe is a long tube in the ground that connects the magma chamber to the earth's surface. molten rock and gas leave the volcano through an opening called a vent. a lava flow is the area covered by lava as it pours out of the vent. a crater is a bowl-shaped area that may form at the top of the volcano around the central vent. |
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Term
| types of volcanic eruptions |
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Definition
the silica content of magma helps to determine if a volcanic eruption is quiet or explosive. the greater the silica content of magma, the thicker it is.
silica is something composed of silicon and oxygen, one of earth's most abundant materials |
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Term
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Definition
| magma flows easily; gas dissolved in the magma bubbles out gently; produces two types of lava- pahoehoe, aa; examples: hawaii, iceland |
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Term
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Definition
fast moving, hot lava
surface looks like a solid mass of wrinkles, billows, rope-like coils |
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Definition
coooler, slower moving
when it hardens, forms a rough surface consisting of jagged lava chunks |
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Term
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Definition
| magma is thick and sticky; magma slowly builds up in the volcanoes pipe; dissolved gases cannot escape; trapped gases build up pressure until they explode; a pyroclastic flow occurs when an explosive eruption hurls out ash, cinder, bombs and gases |
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Term
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Definition
active- is erupting or has shown signs that it may erupt in the near future; dormant- does not show signs of erupting in the near future;
extinct- unlikely to erupt |
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Term
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Definition
| groundwater heated by a nearby body of magma rises to the surface and collects in a natural pool |
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Term
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Definition
| forms when rising hot water and steam become trapped underground in a narrow crack; pressure builds until the mixture suddenly sprays upward, clearing the crack |
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Definition
thin layers of lava pour out of a vent and harden on top of previous layers
example: hawaiian islands |
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Term
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Definition
| form when cinders from a vent pile up around a vent forming a steep cone-shaped mountain |
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Term
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Definition
| layers of lava alternate with layers of ash, cinders and bombs |
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Term
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Definition
| a large hole at teh top of a volcano formed when the roof of a volcano's magma chamber collapses |
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Definition
| a slab of volcanic rock formed when magma forces itself across rock layers; vertical rock formation |
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Definition
| a slab of volcanic rock formed when magma squeezes between layers of rock; horizontal rock formation |
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Definition
| a mass of rock formed when a large body of magma cooled inside the crust |
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Term
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Definition
| rising magma within the crust is blocked by layers of rock; magma forces layers of rock to bend upward into a dome shape; example: black hills |
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