Geology Test #1

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Continental Drift-

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- A hypothesis, credited by Alfred Wegener- he said that all present continets once existed as a single supercontinet. Beginning about 200 million years ago, the supercontinent began breaking into smaller continets, which then "drifted" to present postions. njhyt

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Plate Techtonics-

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Theory- earths outter shell consists of individual plates that interact in various ways and thereby produce earthquakes, volcanos, moutanins and the crust itself.

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Evidence of Alfred Wegener hypothesis of Continetal Drift-

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- The continetal Jigsaw Puzzle- shorelines of continets match geometrically.

- Matching moutain ranges- continets have matching rock types & structers. Mountain belts trend to occur on one side of the continets.

- Fossil match across the sea- Continets have matching fossil types--i.e--lystrosarous-meaosaurcs-glossopteris

-Paleoclimate- study of acinet climates

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This is TRUE:

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- Earth's magnetic field reverses over geologic time.

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Beneath Earth's lithosphere, the hotter, weaker zone known as the asthenosphere allows for motion of Earth's rigid outer shell.

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asthenosphere

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Which boundary is characterized as a long, linear rise in the seafloor, with shallow earthquakes and volcanic activity found along its length?

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-divergent boundary

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wHAT ARE Deep-ocean trenches are formed by?

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-the subduction of lithosphere into the asthenosphere

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Where geographically can you find transform faults?

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-near the Mid-Atlantic Ridge and along the San Andreas transform plate boundary

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Which of the following is one of the remarkable realizations associated with the discovery of seafloor spreading?

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-The crust of the oceans is very young relative to the age of the continental crust.

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The Hawaiian Islands were formed as a result of WHAT?

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-a mantle plume

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What forces drive plate tectonic motion?

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-Convective flow in the mantle
-Subduction of the cold, dense lithosphere

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DIVERGENT PLATE BOUNDARIES:

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<---....--->
-Most are located along the crests of mid-oceanic ridges
-Constructive Margins
-Zone of seafloor spreading
-Plates grow along these boundaries
- located along the crests of oceanic ridges & can be thought of as CONSTRUCTIVE PLATE MARGINS, b/c this is where NEW ocean floor is generated.

- 2 adjacent plates move away from each other, producing long narrow fractures in the ocean crust. RESULT FROM THIS- hot rock from the mantle below fill the voids left as crust being ripped apart. The molten material cools to produce new silvers of the seafloor. Adjacent plates spread apart, & new oceanic lithosphere forms between them.

-2 plates that are moving apart from each other
RESULT: creation of a new ocean floor with submarine volcanoes; mid-oceanic ridge; small to moderate earthquakes

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DIVERGENT PLATE BOUNDARIES- CONTINETAL RIFTING:

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- A Linear zone along which continetal lithosphere stretches & pulls apart. It's creation may mark the beginning of a new ocean basin.

- Splits landmasses into 2 or more smaller egmets along a continteal rift.

- EX- E. AFrica Rift Valleys
- Rhine Valley in Northern Europe

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CONVERGENT PLATE BOUNDARIES:

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--->...<---
-Plates run into each other
-Destructive margins
-The entrance to subduction zones is in deep ocean trenches
-Plate is destroyed along the boundary
- 2 plates move together, resulting in oceanic lithosphere being thrust beneath an overriding plate, eventually to be reabsorbed into the mantle. It can also involve the collison of 2 continetal plates to create a mountain system.

-older/cooler portions of oceanic plates r returned to the mantle at these DESTRUCTIVE PLATE MARGINS

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CONVERGENT PLATE BOUNDARIES-- oceanic- continteal convergence:

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- Along the decending plate, partial melting of mantle rock generates magma.

- Continental volcanic arc

- ex- Andes
- Cascades

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CONVERGENT PLATE BOUNDARIES-- oceanic-oceanic convergence:

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- Often forms volcanoes on the ocean floor. If the volcanos emerge as islands, a VOLCANIC ARC is formed.

- Ex- Japan
- The Aleutian islands
- Tonga Islands

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CONVERGENT PLATE BOUNDARIES-- continteal- continteal convergence:

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- Subduction can bring 2 continets together. Less dense, buoyant continteal lithosphere does not subduct.

-forms moutinans

-both plates r contienteal

- Ex- Himalayes
- Alps
- Appalachians

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TRANSFORM FAULTS:

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- Plates slide past one another and NO NEW lithospehre is created or destroyed-- CONSERVATIVE PLATE MARGINS.

- Most join segments of a mid-ocean ridge along breaks in the oceanic crust known as fracture zones.

- A few (san andreas fault & the Alpine Fault of New Zealand) cut through contintial crust.

-small to large earthquakes

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Importance of Plate Tectonics:

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- Earths majior surfaces processes

- Distrubtion of earthquakes, volcanos, & mountains.

-Distrubution of ancient organisms and mineral deposits.

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PLATE TECTONICS: THE NEW PARADIGM:

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- 7 MAJIOR lithospheric plates

- plates r in motion (5 cm/yr) & r continually, changing in shape & size

- Several plates include an entire continent plus a large area of seafloor.

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When moving away from a divergent boundary in either direction, which of the following statements is true?

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-The rocks increase in age.

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Which of the following geologic processes and/or phenomena is not found at transform plate boundaries?

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- Volcanos

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Who came up with the Seafloor spreading hypothesis?

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-Harry Hess early 1960's

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PLATE TECTONICS: THE NEW PARADIGM:-

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- The seafloor spreading hypothesis- was first proposed in the 1960's by Harry Hess, suggested that the new oceanic crust is produced at the crests of mid-ocean ridges, which r the sites of divergence.

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Earths layers by phycical properties:-

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- LITHOSPHERE (RIDGED OUTTER LAYER)- uPPERmost mantle & overlying crust

-ASTHENOSPHERE- weaker region in the mantle (solid, but mobile)

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What boundary are the sites of the largest earthquakes on earth?

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-convergent

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When geologists speak of the "lithosphere," they really mean "crust." (T/F)

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-FALSE

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Earth's inner core is molten (T/F)

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-FALSE

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Large damaging earthquakes may occur anywhere on Earth at any time without warning. (T/F)

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-FALSE

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Volcanic activity is common at divergent plate boundaries. (T/F)

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- TRUE

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Volcanic activity is common at convergent plate boundaries. (T/F)

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-TRUE

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Volcanic activity is common at transform plate boundaries. (T/F)

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-FALSE

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Earth's lithosphere is rigid and unchanging. (T/F)

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-FALSE

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Geologists understand how earthquakes are generated, but cannot predict when they will occur. (T/F)

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-TRUE