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6th Grade Science Chapter 1: Earthquakes and Volcanoes

Terms in this set (51)

Main parts of the earth
-Core
• Inner core
• Outer Core
- Mantle
-Crust
Lithosphere
the crust and upper area of the mantle
Plates
float on the partly melted rock in the earth's mantle
Theory of Plate Tectonics
the idea that the earth's crust is made up of moving plates
Plate boundaries
places where the boundaries meet.
Pangea
A single large landmass that scientists believe the earth could have been at one time
Earthquake
an event that occurs when rocks along the plate boundaries shift suddenly and release their stored energy
Faults
breaks in the earth's surface along which rock can move
Thrust (reverse) fault
occurs where rocks push together until they force a section of rock upward (example - Himalaya Mountains in Asia)
Normal fault
As rocks move apart, a section of rock may fall between the separating rocks. (example - Great Rift Valley in Africa)
Strike-slip fault
occurs as rocks move horizontally past each other (example - San Andreas Fault in California)
Focus
beginning point of an earthquake
Seismic waves
vibrations that flow out from the focus of an earthquake
Epicenter
the point on the surface of the earth directly above the focus
Body waves
seismic waves that occur beneath the surface of the earth
P waves (primary waves)
*type of body wave
*move quickly through both the solid and liquid material in the earth's interior
*can be felt on the side of the earth opposite from the focus of an earthquake)
S waves (secondary waves)
*type of body wave
*move more slowly
*cannot move through the liquid material in the earth
Seismologists
scientists who study the movement of the earth
Surface waves
slowest moving and most destructive waves on the surface of the earth
-Love waves and Rayleigh waves
Seismograph
machine used to detect, time, and measure the movements of the earth
Mercalli scale
based on the amount of destruction that an earthquake causes to manmade structures
Richter scale
measures the magnitude, or strength of the seismic waves of an earthquake
Magnitude
the amount of energy released from an earthquake
Building for Earthquakes
-Foundation
-Building materials
-Design
Tsunamis
a series of giant waves caused by an earthquake, volcano, or landslide occurring under or near the ocean
Volcanic eruptions
Mount St. Helen in Washington (1980)
Magma
molten rock and gases beneath the earth's surface
Volcano
a crack in the earth's crust through which magma and gases come to the surface
Volcanologists
scientists who study volcanoes
Magma chambers
pockets of molten rock deep in the earth's lithosphere
Lava
magma that has broken through the surface of the earth
Locations of Volcanoes
1. Ring of Fire - the ring of volcanoes found in an area around the Pacific Ocean
2. Mediterranean Sea (Mount Etna)
3. Underwater - called submarine eruptions and are 20 times more frequent than eruptions on land
Hot spots
places where a pool of intensely hot magma rises toward the surface
Shield volcano
-has gradually sloping sides and looks like upside-down saucers
-generally not explosive
Cinder cone volcano
-resembles a hill more than a mountain
-has a bowl-like crater at the top and usually contains one main vent
-eruption tends to be explosive
-showers bits of ash and lava, called cinder, into the air
Composite cone volcano
-large, symmetrical, cone-shaped
-has steep sides that can measure several thousands of meters high
-made of layers of hardened lava and tephra
(tephra - mixture of cinders, ash, and rock)
-has explosive eruptions
Active
one that has erupted at some point during a recorded time period and is expected to erupt again
Dormant
has erupted in the distant past but is currently inactive and not expected to erupt again
Extinct
does not have a recorded eruption and is not expected to erupt in the future
Mount Vesuvius, Mount Tambora, and Mount Katmai
volcanoes that were once considered
extinct but suddenly erupted killing many people.
Hawaiian eruption
-runny lava and little or no cinder, ash, and steam
-quiet eruption that may continue for a long period of time
Strombolian eruption
-produces a fountain of lava that runs down the sides
-non-violent eruption
Vulcanian eruption
-violent eruption
-causes a loud explosion that sends lava, ash, cinders, and gas into the air
Pelean eruption
-produces a Pyroclastic flow (avalanche of red-hot dust and gases) which races down the side of the volcano
-named after Mount Pelee on the Caribbean island of Martinique
Plinian eruption
-most powerful
-spews out lava, gases, ash, and debris very high into the atmosphere
Pyroclastic flow
avalanche of red-hot dust and gases
Debris flow
occurs when part of the mountain collapses and mud and rock fragments surge down the mountain
Igneous rock
formed from volcanic magma and lava
Hot spring
water heated by magma that rises to the earth's surface
Geyser
a hot spring that periodically blows steam and hot water into the air (Old Faithful in Yellowstone National Park)
Mud pot
a hot spring that has more mud than water
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