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106 Cards in this Set
- Front
- Back
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Explain why the rigid Earth theory is no longer considered correct
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-Scientists believes that Earth's crust was static and continents and oceans were in a fixed position only to be modified by changes in sea levels
-They believed Earth's crust was too rigid to allow large scale movement |
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What theory has replaced the rigid Earth theory?
Who first proposed this theory? |
-Continental drift
-Wegener, Bacon, and Ortelius |
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How did Continental theory evolve and what evidence has been used to support this theory?
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-continents fit together like puzzle pieces (Africa and America)
-Seeds and animals found in different places -sea floor spreading and plate tectonics |
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Pangaea
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-massive supercontinent existing 225 mya then broke apart into large sections
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Explain how the presence of the Mid-Atlantic Ridge supports the theory of plate
tectonics. |
-plates are being pulled along by subduction of cold, dense oceanic lithosphere into the asthenosphere
-it is in an area where new crust is being made |
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Why does the rock get increasingly older as you move away from the mid-ocean ridges?
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-mid-ocean ridges are where magma bubbles up and creates new crust on the ocean floor
-it then spreads away laterally -oceanic trenches is were older crust descends during subduction where it is "recycled" |
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Divergent plate boundary
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-2 plates diverge from one another
-magma comes up between plates producing a line of volcanic vents -mid-ocean ridges "spreading" -continental rift valleys- develop within a continent -divergent boundaries are "constructive" |
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Convergent plate boundary
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-2 plates converge toward one another
-"destructive" (mnts, volcanoes, ocean trenches) -results in removal or compression of surface crust -3 types of convergent boundaries 1). oceanic-continental 2). oceanic-oceanic 3). continental-continental |
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Transform plate boundary
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-2 plates slide laterally past one another
-occurs along transform faults (strike slip) -they don't create or destroy crust -associated with seismic activity (shallow earthquakes) -found along the mid-ocean ridge system |
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Explain the Hawaiian Islands in terms of mantle plumes.
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-the chain of islands is being formed as the Pacific plate moves over a stationary plume of magma rising from the mantle
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Why is there such a concentration of earthquakes and volcanoes around the margin of the Pacific Ocean? What is this called?
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-Pacific ring of fire
-plate boundaries are found all around the Pacific basin -subduction zones, transform and divergent boundaries |
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How were the Himalayas formed?
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-India collided with Eurasia
-Continental-continental collision |
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How were the Andes formed?
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-Oceanic-continental convergence
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Active volcano
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-if it erupted at least once within historical times and is likely to do it again
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Where are most of the volcanoes located in the United States?
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-Cascade Range Pacific northwest
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What were some of the effects of the Mt. St. Helens’ eruption?
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-reduced elevation by 1300ft
-spread ash 22,000 miles -$1 billon cost -57 people died |
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Why are volcanoes sometimes considered beneficial?
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-water is released as water vapor during eruptions
-magma and ash can mix with soil to provide nutrients for plant growth |
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What is North America’s most famous caldera? How was it formed?
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-Crater Lake
-formed during an eruption, the walls weakened and collapsed -emptied the magma chamber and filled with water |
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Graben
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-a block has been downthrown (valley)
-straight steep-sides -fault scarps on both sides -bounded by parallel faults |
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Horst
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-uplift of a block
-results in land on both sides being uplifted (mountain) |
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Diastrophism
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-AKA Tectonism
-Rocks may be bent or broken because or pressure in the crust of mantle -twisting |
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Folding
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-the bending of crustal rocks by compression or uplift
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Faulting
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-the breaking or fracture of crustal rocks by compression
-horizontal or vertical, or both |
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Anticline
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-ridge shaped up-fold of rock
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Syncline
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-downward fold "dip" of rock
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Overturned
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-pushed so much from 1 side it becomes over steepened
-reverse orientation on the other side |
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Overthrust
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-very low angle of dip and large total displacement
-older rock to override the younger rock |
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Which mountain range is a series of ridge and valleys caused by folding?
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-Appalachian Mountains
-up-fold anticlines produce ridges -down-fold syncline produce valleys |
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Magma
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-Molten material below the Earth's surface
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Lava
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-molten magma that is extruded ONTO the surface of Earth
-then cools and solidifies -slow moving -flows like stacking |
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Lahar
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-volcanic mudflow
-fast moving muddy flow of ash and rock fragments |
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Pyroclastic material
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-solid rock thrown into the air by volcanic explosion
-high speed avalanche of hot gases, ash, and rock emitted |
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Flood basalt
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-out pouring of basaltic lava that can cover a large area of Earth
-Mass extinction |
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Where are prominent flood basalt formations located?
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-Deccan Traps, India
-Siberian Traps -Columbia River plateau, N. America |
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What is the difference between an earthquake’s focus and its epicenter?
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-the strongest shocks and vibrations are felt on the ground above the focus at the epicenter
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Batholith
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-the largest and most amorphous of igneous intrusions
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Caldera
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-large steep-side circular depression
-resulting from explosion or collapse of a volcano |
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Dike
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-vertical sheet of magma that is thrust upward into preexisting rock
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Normal fault
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-results from tension
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Reverse fault
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-produced from compression
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Strike slip fault
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-side to side horizontal movement
-shear stress |
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Fault scarp
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-steep cliffs
-vertically displaced block |
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Hot spot
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-an area of volcanic activity within the interior of a lithospheric plate
-magma rising up from the mantle |
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Laccoliths
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-form of intrusion
-produces slow flowing viscous felsic magma |
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Monocline
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-one sided fold
-connecting 2 horizontal inclined strata |
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Oceanic trenches
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-Narrow and deep
-occur around margins of ocean basins |
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Sag pond
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-caused by collection of water from springs or runoff into sunken ground
-results from crushing of rock in an area of fault movement |
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Stock
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Smaller igneous intrusion of depth
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Subduction
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-descent of the edge of an oceangoing plate under the edge of an adjoining plate
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What are the two primary types of waves generated by earthquakes?
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-surface waves and body waves
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Name two types of body waves
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-P waves and S waves
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Where do body waves and surface waves travel?
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-within Earth, and surface waves travel along Earth's surface
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What do vertical and horizontal surface waves have in common?
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-Both waves travel along Earth's surface and decrease in amplitude with depth below the surface
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How do rocks within Earth change as P waves pass?
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-expand and contract as P waves pass.
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How does rock within Earth change as S waves pass?
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-displaced up and down as S waves pass.
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How are S waves and vertical surface waves different?
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-S waves are body waves, amplitude of S waves does not decrease with depth
-vertical surface waves are surface waves, amplitude of vertical surface waves does decrease with depth |
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what are the four primary zones in Earth's interior?
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-crust, mantle, outer core, inner core
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Which of the following statements about seismic wave ray paths is most accurate?
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-Seismic waves move along curved ray paths because of changing properties of rocks.
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Why do we believe Earth's outer core is a liquid?
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-S waves do not travel through the outer core
-P waves slow down and refract at the boundary between the mantle and the outer core. |
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Why do geologists believe the inner core is solid?
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-P waves refract at the boundary between the outer core and inner core
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What is a seismograph?
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-an instrument used to record earthquake waves
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When will the first earthquake waves arrive at a seismograph station?
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-a short time after the earthquake occurs
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What is the longest amount of time that might occur between earthquake occurrence and arrival of the first earthquake waves at a seismograph?
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-several minutes
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How do plates move at divergent plate boundaries?
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-Plates move apart.
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How do plates move at convergent plate boundaries?
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-Plates move together
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How do plates move at transform plate boundaries?
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-Plates move side by side.
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where do both earthquakes and volcanic eruptions occur?
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-at divergent plate boundaries
-at convergent plate boundaries |
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What forms at divergent plate boundaries?
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-new oceanic lithosphere
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where do volcanoes form in subduction zones?
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-on the overriding plate, away form the convergent boundary
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Why are volcanoes not found at transform boundaries?
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-Transform boundaries do not cause changes to the pressure, temperature, or composition of the mantle.
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Where are tectonic plates located?
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-at Earth's surface
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What are the three types of plate boundaries?
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-divergent, convergent, and transform
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Which plate boundary is NOT associated with volcanic eruptions?
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-transform
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Which phenomenon can explain the presence of volcanoes in the middle of the Pacific Ocean?
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-hot spots
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Which type of plate boundary is most closely associated with uplifting continental regions and mountain building?
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-convergent boundaries
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Which type of plate boundary is most closely associated with the formation of new ocean floor?
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-divergent
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Which of the following statements about Earth's magnetic field is most accurate?
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-Earth's magnetic field switches polarity at irregular time intervals.
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How often does the Earth's magnetic field switch polarity?
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-every 100,000 to several million years
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How are normal polarity and reverse polarity of Earth's magnetic field different?
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-A compass points toward the North Pole during normal polarity
-to the South Pole during reverse polarity. |
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Which mountain belt lies to the north of India?
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-the Himalayas
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what are the Himalayan mountains composed of?
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-folded and faulted rock
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Which type of plate boundary exists between India and Asia today?
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-a convergent boundary
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Why didn’t India subduct under Asia?
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-The two continents have similar densities.
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Did any subduction occur during the collision of India and Asia?
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-Yes; ocean basin between these two continents subducted under Asia.
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Which location is the result of oceanic-continental convergence?
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-he Cascades and Mt. St. Helens
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What is a terrane?
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- slice of lithosphere that has been added to the margin of a continent during plate collision
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Where does most terrane accretion occur?
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-continental-oceanic subduction zone
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Why are terranes added to continental margins, rather than subducting under them?
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-Terranes are too buoyant to subduct
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What geologic process is related to caldera formation?
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-volcanism
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How do calderas form?
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-Calderas form when the summit of a volcano collapses
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Why does Crater Lake have an island in it?
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-The volcano is still active, and a new volcanic peak has formed
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3 types of volcanoes
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-Cinder cone
-Shield volcano -Composite volcano |
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Cinder cones are made of________.
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-pyroclastic deposits
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how often do most cinder cones erupt?
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-cinder cones erupt once
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What are shield volcanoes generally made of?
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-Basalt flows
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What is the range of shield volcano height?
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-300 to 10,000 meters
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What are composite volcanoes made of?
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-Pyroclastic deposits
-Basalt flows |
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What type of magma erupts out of dome complexes?
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-Felsic magma
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What type of volcanoes are the tallest?
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-Shield volcanoes
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What is the range of dome complex height?
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-500 to 2,000 meters
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What are rocks below and above a fault called?
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- footwall below
-hanging wall above |
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Which type of force is responsible for normal fault formation?
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-tensional force
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Which type of force is responsible for reverse fault formation?
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-compressional force
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Which type of force is responsible for normal strike-slip formation?
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-shear force
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Which type of fault has NO vertical motion of rocks associated with it?
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-strike-slip fault
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What is an explosive volcanic eruption of hot gases, ash, and rocks that burns and buries things in its path?
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-Pyroclastic flow
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