EARTH SCIENCE at SPRING VALLEY HIGH SCHOOL
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UNIT II: THE DYNAMIC CRUST
«1. List direct/indirect evidence of crustal movement
a. Sedimentary rocks at high elevations suggest past of the crust.
b. Shallow-water marine fossils found today at both high elevations and at great ocean depths indicate changes in of the crust.
c. Tilted and folded rock (sedimentary layers) suggest past crustal movement.
d. Rock faults, volcanoes, displaced strata, beaches, and changes in elevations are all indications of crustal change and movement.
«2. Describe evidence of continental drift
a. Zones of frequent earthquakes and volcanic activity can be located on the Earths surface. ex/
b. In many places the zones of crustal activity are associated with high, young ranges and deep ocean .
c. Igneous rock near the center of the ocean ridges is than the igneous rock farther from the ridges.
d. Mid-ocean ridges, the sites of sea-floor spreading, are found in all major oceans and represent more than 20 percent of Earth's surface. These broad features are characterized by an elevated position, extensive faulting, and volcanic structures that have developed on newly formed oceanic crust. Most of the geologic activity associated with ridges occurs along a narrow region on the ridge crest, called the rift zone, where magma from the moves upward to create new slivers of oceanic crust.
e. The Earths magnetism seems to have itself many times in the past. Strips of rock parallel to the ocean show patterns of reversal of magnetic polarity that match the reversals of the Earths magnetism.
f. The shapes of the continents, combined with comparisons of rocks and minerals, mountain formations, fossils, past climates, and rock magnetism, suggest that the continents were at one time and have since drifted apart.
«3. Define terms regarding Earthquakes
a. - the shaking of Earth's crust caused by a sudden release of energy.
b. - a crack in the crust along which movement has occurred.
c. - the point within the Earth where an Earthquake originates
d. - the point on Earths surface directly above the focus
«4. Explain measurement of Earthquake energy
a. - an Earthquake generated wave
b. - the study of Earthquakes
c. - someone who studies Earthquakes
d. Seismic - someplace where seismic activity is being recorded
e. - an instrument that detects and records seismic waves
f. - the recording of an Earthquake (on paper) made by a seismograph
g. scale- A scale, from 1 to 10, that measures the amount of energy ( ) released during an Earthquake on the basis of the amplitude (height of a wave) of the highest peak recorded on a seismogram. It is a scale, which means that a Richter 3 is 10 times greater than a Richter 2, and a Richter 4 is 100 times as great as a Richter 2. Each unit increase in the Richter scale represents a 10X increase in the amplitude recorded on the seismogram and a 32X increase in energy released by the Earthquake:
1.0 = 30 pounds dynamite= Large Blast at a Construction Site
1.5 = 320 pounds dynamite
2.0 = 1 ton dynamite= Large Quarry or Mine Blast
2.5 = 4.6 tons dynamite
3.0 = 29 tons dynamite
3.5 = 73 tons dynamite
4.0 = 1,000 tons dynamite= Small Nuclear Weapon
4.5 = 5,100 tons dynamite= Average Tornado (total energy)
5.0 = 32,000 tons dynamite
5.5 = 80,000 tons dynamite= Little Skull Mtn., NV Quake, 1992
6.0 = 1 million tons dynamite= Double Spring Flat, NV Quake, 1994
6.5 = 5 million tons dynamite= Northridge, CA Quake, 1994
7.0 = 32 million tons dynamite= Japan Quake, 1995; Largest Nuclear Weapon
7.5 = 160 million tons dynamite= Landers, CA Quake, 1992
8.0 = 1 billion tons dynamite= San Francisco, CA Quake, 1906
8.5 = 5 billion tons dynamite= Anchorage, AK Quake, 1964
9.0 = 32 billion tons dynamite= Chilean Quake, 1960
10.0 = 1 trillion tons dynamite= (San-Andreas type fault circling Earth)
h. scale- a scale, from I to XII (1 to 12), of Earthquake (damage).
Scale I= Not felt except by a very few
Scale II= Felt only by a few persons on upper floors
Scale III = Felt indoors
Scale IV = Hanging objects swing
Scale V= Felt outdoors
Scale VI= Felt by all, many frightened & run outdoors
Scale VII= Difficult to stand
Scale VIII= Damage slight in specially designed structures
Scale IX= Damage considerable in specially designed structures
Scale X= Ground cracked, rails bent
Scale XI= Bridges destroyed, broad fissures in ground
Scale = Damage total
i. Earthquakes and volcanoes present geologic hazards to . Loss of property, personal injury, and loss of life can be by effective emergency preparedness.
«5. Compare & contrast Earthquake waves
a. - Primary, or compressional, Earthquake waves formed by alternate compression and expansion of rock. The vibration of the particles is to the direction of travel of the waves. P waves travel faster than any other seismic waves, and can travel through solids, liquids and gases (sound waves).
b. - Secondary, or shear, Earthquake waves, which can travel through solids, but not or gases. A seismic wave with a vibration that is to the direction of wave travel. S waves travel than P waves.
«6. Interpret inferred properties of Earths interior using Earthquake time/travel chart
a. Differences in travel times of seismic waves can be used to determine the between a seismic station and the of an Earthquake.
b. Seismograms from at least seismic stations are needed to find the exact location of an epicenter.
c. The of a seismic wave varies with the physical properties of the material through which the wave is traveling. Ex/ Waves travel faster through denser rock.
d. Analysis of seismic data leads to the inference that zones (crust, mantle, and inner core) and a zone (outer core) exist within the Earth.
e. The Mohorovicic discontinuity, or , is the boundary between the crust and the mantle.
f. The average thickness of the continental crust is than the average thickness of the oceanic crust.
g. The oceanic and continental crusts have different compositions. (Oceanic= , basaltic, and high density; Continental=felsic, , and density)
h. The zone is a belt around the Earth where neither P nor S waves are received from a particular Earthquake.
i. Seismic data suggest that the Earths core is composed of and . Denser elements sank to Earths center.
j. The density, temperature, and pressure of the Earths interior with depth.
«7. Explain the cause of plate tectonics
a. The theory of plate tectonics states that the solid (crust and rigid mantle) consists of a series of plates that float on the partially molten (plastic mantle).
b. currents within the asthenosphere are thought to move the plates.
c. Why is the Earth's interior hot?
i. The decay of Uranium (U), Thorium (Th) and Potassium (K)
ii. Leftover from Earths formation and meteorite impacts
iii. Plate friction
«8. Describe the types and features of plate boundaries
a. plate boundary- A boundary between two lithospheric plates where the plates are sliding horizontally past one another. Ex/ San Andreas Fault in California
b. plate boundary- A boundary where two lithospheric plates move away from each other. Ex/ Mid-Atlantic Ridge
c. plate boundary- A boundary where two lithospheric plates are coming together:
i. Oceanic- Plate Boundary (Ex/ Peru-Chile Trench)
ii. -Oceanic Plate Boundary (Ex/ Aleutian Trench)
iii. Continental- Plate Boundary (Ex/ Himalayan Mountains)
d. Zones exist at convergent plate boundaries when one plate dives down beneath another plate. This process creates trenches, island arcs, and volcanic mountain ranges.
e. - a geologic 'hot spot' is an area in the middle of a crustal plate where magma is rising. Hot spots are as the plates move above them. Magma breaks through and produces undersea . Some of these volcanoes build up to the surface of the ocean and become . Over millions of years the plate may move across the 'hot spot.' The original volcano becomes but a new volcano will begin to form in the area of the 'hot spot.' A hot spot can also exist under the crust (Yellowstone National Park in northwestern Wyoming).
f. Hawaiis Hot Spot- The Hawaiian islands get to the northwest, indicating that the Pacific Plate is moving to the northwest. The Hawaiian Ridge-Emperor Seamounts chain extends some 6,000 km from the "Big Island" of Hawaii to the Trench off Alaska. A sharp bend in the chain indicates that the motion of the Pacific Plate abruptly changed about 43 million years ago, as it took a more westerly turn from its earlier northerly direction. On the seafloor to the of Hawaii is an active volcanic area with periodic eruptions. This area is called Loihi and will be the site of the next Hawaiian Island more than 10,000 years from now.
«9. Locate and identify plate boundaries and
tectonic features- (See pages 5, 9 and 10 in your Earth Science Reference Tables.)
«10. Understand that plate motions have resulted
in global changes in geography, climate, and the patterns of organic evolution.
a. looks very different today than it did in the past
b. Places near the (warm) today may have been near the (cold) in the past, and vice versa.
c. When the plates separated, unique life forms were able to on each continent.