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Earth Science Chapter 12 and 13 Test Review

Terms in this set (88)

Earthquake
movement of the ground caused by a sudden release of energy
Fault
break in a body of rock along which one block slides relative to another
Locked fault
fault in an immobile state until the rocks suddenly grind past each other
Elastic rebound
the sudden return of deformed rock to its undeformed shape
Focus
location of FIRST motion of an earthquake
Epicenter
point on Earth's surface directly above the Earthquake Focus
-to locate, scientists perform triangulations based on data from seismograph stations
Shallow focus
earthquakes that do the most damage with foci 70 km from surface
Intermediate foci
70-300 km from surface
Deep foci
300 -650 km from the surface
Seismic wave
Their speed and direction is affected by composition of Earth's interior
-As rocks slip, they release energy in form of vibrations called this
Body wave
seismic wave that travels through the body of a medium-2 types
P wave
also known as "compression waves"
- fastest seismic body wave
- can travel through solid, liquid, + gas
- travels fastest through very rigid, not easily compressed material
S wave
2nd fastest seismic body wave
also known as "shear" wave
can only travel through solids
Surface wave
a seismic wave that travels along the surface of a medium, potentially most damaging, slowest moving, 2 types (Love and Rayleigh)
Shadow zone
Location on the surface where no direct waves from an earthquake can be detected in the area
Fault zone
A region of numerous, closely spaced faults
Seismograph
Instrument that records ground vibrations
Seismogram
A tracing of earthquake motion that is recorded on a seismograph
Magnitude
Measure of strength of an earthquake
Richter Scale
1934, Charles F. Richter, a magnitude scale that measures ground motion
Moment Magnitude
scale that more accurately measures magnitude of earthquake
-magnitude scale based on the size of fault area that moves, how far fault block moves, and the rigidity of the rock
-More closely related to the cause of an earthquake
Intensity
Amount of damage
Modified Mercalli Scale
a scale in Roman Numerals 1-12 that measures earthquake intensity
Tsunami
giant ocean waves
-epicenter of tsunami causing earthquake is on the ocean floor
-caused by undersea earthquakes, landslides, volcanic eruptions
Seismic gap
area along a fault where few earthquakes have recently occurred, but major earthquakes occurred in the past
Foreshock
small earthquakes that come before the actual earthquake - seconds to weeks
Record and analyze arrival time of P and S waves at several seismograph stations
How do scientists find the distance to the epicenter?
Gets higher
What happens to a tsunami as it gets closer to shore?
Stay away from windows, glass, electrical, Get under a sturdy table or counter
If indoors during an earthquake, what should you do and not do?
The type of ground beneath it- solid pack best
How buildings respond to seismic waves depends on?
sway and collapse or if taller, tip over
What happens to buildings during an Earthquake?
Seismic gaps, foreshocks, rock changes
What three things are studied to forecast an earthquake?
Unreliable
How reliable is our ability to predict an earthquake?
At plate boundaries - experience great stress
Where to earthquakes occur?
Mid Ocean Ridge, plates pull apart-spreading motion causes earthquakes
Subduction Zones -(convergent Oceanic Environment)
Continental Environments -converging, divurging, or moving horizontally creates stress-can trigger quake
Earthquakes are the result of tectonic stresses in Earth's crust which occur in which 3 main tectonic settings?
Crust, mantle, core
What are the 3 Compositional Layers of Earth?
Lithosphere, Asthenosphere, Mesosphere, Outer Core, Inner Core
What are the 5 Mechanical Layers of Earth?
intense stress where plates separate, collide, subduct, or slide past each other
Why do fault zones form at plate boundaries?
A major earthquake and volcanic zone
The Pacific Ring of Fire is known as....
Be Prepared, Protect, Be Cautious
What are the rules for before and after an Earthquake?
on ocean floor in a subduction zone along edge of continent where plate is subducted
Where does a "trench" form?
Magma
liquid rock produced under Earth's surface when temperature of rock rises above its melting point
Magma forms
-temperature of rock rises above melting point of minerals in rock
-Pressure removed from rock decreases melting point
-Adding fluids (H2O) during subduction decreases melting point
It is less dense than rock
magma rises through the crust to the surface because
Volcanism
any activity that includes the moving of magma onto Earth's surface
Lava
magma erupting onto Earth's surface, forms rock when it cools and solidifies
Volcano
a vent in Earth's surface
Where volcanoes occur
Subduction Zones -trench
Mid Ocean Ridges -new lithosphere formed (underwater pillow lava, fissures)
Hot Spots- area of volcanism in lithosphere from mantle plume - Ex. Hawaii - hot spot stays, lithosphere moves, new volcano forms- chain
Pacific Ring of Fire
major volcanic and earthquake zone(formed by subduction plates)
Subduction zone
where volcanoes can form, where one tectonic plate moves under another
Trench
formed on the ocean floor where one plate subducts under
Island arc
forms when oceanic lithosphere subducts beneath oceanic lithosphere
Mid-Ocean ridge
largest amount of magma comes to surface where plate move apart-divergent boundary, tension stress
Pillow lava
rapidly cooling lava that forms on mid ocean ridges at underwater volcanoes
Fissures
cracks through which lava flows to Earth's surface (Iceland)
Hot spots
a volcanically active area of Earth's surface, commonly far from tectonic plate boundary
Mantle plumes
a column of hot, solid material from the deep mantle, form "Hot Spots" when they rise and reach the lithosphere
Igneous rock
rock that forms when magma cools
Intrusive activity
as magma moves upward it comes in contact with overlaying rock, it "intrudes", melting surrounding rock, changes it, fractures it, causes fissures
Plutons
large igneous rock formations, Devils Tower
Dike
small, tabular shaped plutons
Batholiths
large plutons, at least 60+ miles sq
Mafic rock or magma
rich in Mg and Fe, dark in color, commonly makes up oceanic crust
Felsic rock or magma
rich in feldspar and silica, generally light in color
Continental crust
Made of felsic and mafic
Viscosity
Measure of the resistance to flow of magma, determined by mag as composition
Mafic magma
rich in Fe and and Mg, runny, low viscosity, cause quite eruptions
Felsic magma
rich in feldspar and silica, sticky lava, high viscosity, trapped dissolved gases produce explosive eruptions
Lava flow
flow of lava with low viscosity
Pahoehoe
when lava continues to flow after a crust forms, creating a wrinkled crust that becomes volcanic rock-cools and forms smooth ropy texture
Aa
cools thicker surface breaks into jagged chunks, difference in gas content and rate/slope of lava flow
Blocky
higher silica content than aa, more viscous causing cooled lava at surface to break into large chunks, hot lava below continues to flow, looks blocky
Explosive eruptions
produced by felsic magma, a sticky lava with high viscosity+high amount of trapped gas
Pyroclastic material
fragments of rock that form during a volcanic eruption
Volcanic ash
less than 2 mm in diameter
Volcanic dust
less than .25 mm
Lapilli
"little stones" less than 64mm-fall near vent
Volcanic bombs
large, round to spindle shaped lava
Volcanic blocks
largest, form from solid rock, up to size of small house
Crater
funnel shaped pit at top of volcanic, formed by material blown out during explosions
Cone
forms within a crater, when further eruptions cause material to build up around vent
Vent
opening in volcano from which lava flows
Shield volcano
broad at base, great sloping sides, cover a wide area, usually from "quiet" "eruptions, layers of hot, mafic lava gradually build cone, hot spot formed Hawaiian Islands
Cinder cones
very steep slope (40°), rarely more than few 100 meters high, form from explosive eruptions, made of pyroclastic materials
Composite volcano
(stratovolcanoes) large alternating layers from explosive eruptions, then quiet lava flows
Calderas
large circular depression formed by the collapse of a volcanic cone, formed when magma chamber below empties and ground above sinks
Subduction zone
Where volcanoes can form and where one tectonic plate moves under another
Changes in earthquake activity, Bulging of Volcano Surface, Changes in amount and composition of volcanic gases
Three events that signal volcanic eruptions
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