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45 Cards in this Set
- Front
- Back
1912 German meteorologist had an idea about continental movement. His hypothesis* was called ____. Ahead of his time.*
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Alfred Wegener*; Continental Drift* |
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What was Wegener's evidence? |
1) Rocks/mountains are similar across the oceans. 2) Fossils: animals/plants found across continents. 3) Climate (paleoclimatologist how could this be possible?) |
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Other scientists rejected Wegener's hypothesis because he couldn’t explain what was causing the continents to move (a.k.a. HOW?). No Mechanism.*
- He thought rotation of the Earth contributed to movement of continents but physicists said “no.” - Also thought continents plowed through ocean floor but No evidence. |
NO MECHANISM (how?)* |
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1929 geoscientist ___ speculated that ____ occurred in the mantle and could push and pull plates (continents) apart or together. Dense/cool ___ and hot/less dense ___. Stated that ____ contributed to heating. BUT NO EVIDENCE.*
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Arthur Holmes; convection* sinking; rising; radioactive decay* |
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“A monster lays below” the oceans. The largest single feature on the planet and we never saw it before.*After years of mapping the sea floors we find a huge mountain range. Its volcanic, has a ridge down the center and is growing in width. The ___ system is PLANETARY IN SCALE.
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The Mid-Atlantic Ridge; Mid-Ocean Ridge system |
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____in WWII (the 1940’s) began gathering data on the topography of the Pacific Ocean floor using ____. Not real accurate at first but he kept records and pursued the idea after the war.
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Harry Hess; sonar |
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The ____ includes the the crust and a part of the mantle. Below this is the ___. Remember the radius of the earth (distance to the center) is about ____. |
Lithosphere; asthenosphere; 6,400 km or 4,000 miles |
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The primary driving for all this (tectonic plates) is? |
convection |
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Harry Hess used ___ and later ____ to support his ideas of convection as a source for continental drift. ___ came online in the 1950s. |
sea floor mapping; paleomagnetism; Age dating; |
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_____ grains “floating” in hot lava tend to align with Earth’s magnetic field. Cooling at the _____ locks them into the alignment.This record provides information on the past behavior of Earth's magnetic field and the past location of tectonic plates.This is called ____ using volcanic rocks* (sometimes sedimentary). Oceanic rocks are volcanic too.*
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Magnetite;* Curie Point;* Paleomagnetism.* |
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This device could detect small changes in the magnetic field in rocks and geologists can map them.
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Magnetometer
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The earth’s magnetic field switches polarity over geologic time. (At present time, rocks record a normal pattern because the north magnetic pole is in the northern hemisphere). Polarity patterns on both sides of the divergent zone are ____.
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the SAME |
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A divergent margin is another name for the what? |
Spreading center |
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Paleomagnetism + age dating = ? -Technology to age-date rocks appeared in the 1950’s. –Geologists originally thought ocean floors were as old or older than the continental rocks–NOT so! The oceans (floors) are geologically ____ compared to the continents.*** |
STRONG CORRELATION. young; |
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Oceanic crust is very ___ compared to continental crust.* |
thin |
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Polarity patterns on land matched to those at ___. Ages were the ___...nailed it!* |
sea; same |
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Plate Tectonics –Modern Version developed & synthesized in the 1960’s by ____. For the first time in history we can begin to explain the predominant features on Earth and the processes that occur like Mountain ranges and oceans, Earthquakes and volcanis.
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Drummond Matthews, Fred Vine, Lawrence Morley (1963)* |
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4 basic concepts to Plate tectonics Modern version. |
1) The lithosphere is made up of rigid units called plates 2)The plates move 3)Most of the world’s large-scale geological activity occurs AT or NEAR Plate Boundaries (volcanic eruptions/earthquakes) 4)The interiors of plates are relatively quiet geologically, with far fewer & milder earthquakes than occur at plate boundaries (BUT sometimes get a whopper in middle of plate. unusual though). |
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Lithosphere is made up of _ major plates and numerous minor plates. What major ones touch North America? Plates are made up of oceanic and continental lithosphere. Which one is denser?
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7; North American Plate and the Pacific Plate (maybe South American plate too); Oceanic lithosphere is more denser (heavier). |
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What are the boundaries between the plates? Describe them briefly. |
Convergent: where plates collide Divergent: where plates move apart Transform: plates move past one another in opposite directions (horizontal movement via Transform Faults) |
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Similar Evidence to Support Plate Tectonics (or as it was called then, Continental Drift) but with new technology* we have some new* insight.
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-Fit” of the continents same as before: Africa and S. America.
-Distribution patterns same as before: of modern and ancient animals -Distinctive rock types same as before: found at the margins of continents. -Distribution of Paleozoic glaciations same as before. -Polar reversals and wandering as evidenced by paleomagnetics–NEW TECHNOLOGY HELPS! *** |
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Scientists saw potential alignment of continents & Alfred Wegener postulated moving continents & started the concept of “Continental Drift.” He was about 40 years ahead of most others. Couldn’t get support for the concept until new technology helped us discover:
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- Sea Floor Spreading: This was birth of Plate Tectonic Theory & the demise of Continental Drift.*
- Magnetic striping on ocean floor: new crust forms symmetrically along spreading ridges, & is documented by the magnetism “locked” into the minerals found in the crystallized magma at about the time of cooling. –Paleomagnetism became a science all of its own. - Age dating of continental rocks and oceanic rocks |
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The linking together of principles from different disciplines especially when forming a comprehensive theory.
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Consilience* |
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The use of reasoning or arguments that sound correct but are actually false.
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sophistry* |
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There is a map he showed us. It is a map of age dating. Red portions are YOUNG and HOT rocks and Mid Ocean Ridge
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? |
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Today we can "watch" the plates move using ___. |
GPS |
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The biggest mountain range on the planet is? |
under the ocean |
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What's the Plate tectonics theory (the unifying theory of geological SYSTEM)good for? |
It helps explain how the earth works. (Mountain building•Ocean basins getting larger & smaller•Earthquakes•Volcanism•Weathering•Faults•Even atmosphere) |
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-spreading ridges
–rifts within continents -extension sea floor spreading what boundary? |
Divergent |
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Places where there are spreading centers in land. |
Rift Valleys (Ex. East-Africa Rift valley) |
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sometimes you see the map of a divergent boundary ridge being offset (bad alignment) because the process is not perfect. These offset alignments become _____.
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Transform faults |
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_____ drives divergence.* |
Mantle convection |
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-Collision zones: Continent-continent
–Subduction zones: Continent–ocean OR Ocean–ocean (trenches & volcanic arcs form here) |
convergent boundary |
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In subduction, ____ is “dragged” down with the slab and acts as a ___ to partially melt subsurface rocks. This leads to high-silica magma that migrates upwards to fuel the _____. The slab/trench geometries tend to mirror the overlying volcanic arc geometries. They are related.
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water; catalyst volcanic arcs/chains |
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This is a 2nd mechanism. Density of down-going slab acts as a heavy weight. Anchor-like. Will start dragging stuff with it. |
slab-pull |
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When plates move past each other. horizontal. |
Transform |
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San Andreas is a _____. |
transform fault |
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When plates move around they add positive and negative stress with associated strain to the system. Something HAS to give and we see rock crushed, faulted, and folded. Three kinds?
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Lateral faults (left and right) Normal faults Reverse faults |
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What type of fault is this? Overview movement. |
lateral fault. (right if it moves right and left if it moves left). |
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Which one has compression and extension? |
Reverse fault has the hanging wall (makes a triangle right angle). Reverse fault has compression (coming together/shortening) Normal fault has extension (getting longer) |
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If there is curve like in _____ (transform motion and extension together), a basin can form. |
transtension Ex. Fraizer Park (move away) |
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If it squeezes together in ____ (transform motion and compresson), it makes mountains. |
transpression (move closer together) |
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There are two types of folds. |
Anticline (have an A shape) and Syncline (like a U shape) |
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What type of fold is this? |
Anticline |
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What type of fold is this? |
Syncline |