GEOLOGIC ERAS AND PLATE TECTONICS Planet Earth 1.Geologic History 2.Earth’s Interior 3.Tectonic...
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Transcript of GEOLOGIC ERAS AND PLATE TECTONICS Planet Earth 1.Geologic History 2.Earth’s Interior 3.Tectonic...
![Page 1: GEOLOGIC ERAS AND PLATE TECTONICS Planet Earth 1.Geologic History 2.Earth’s Interior 3.Tectonic Plates.](https://reader035.fdocuments.in/reader035/viewer/2022062408/56649e5d5503460f94b5690e/html5/thumbnails/1.jpg)
GEOLOGIC ERAS AND
PLATE TECTONICS
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Planet Earth
1. Geologic History
2. Earth’s Interior
3. Tectonic Plates
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Geologic History
• Precambrian Era
• 4.6 billion years ago until
570 million years
FaultAncient Sea
Igneous Rockmagma Ancient Sea
Sediments
1) Mountain building
2) erosion
-Original Canadian Shield
-First single and multi-celled organisms
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Geologic History
• Paleozoic Era
• 543 to 248 Million Years Ago
Igneous Rock
Erosion
SedimentsSediments Very Old
Lower layers changed into rock
Interior Plains
Appalachian Mountains
1) No Mountains2) Sedimentary Rock uplift
3) Sedimentary RockFolding/uplift
-NA covered by shallow seas-Appalachians formed-1st plants and animals appear on land
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Geologic History
• Mesozoic Era
• 248 to 65 Million Years Ago
Mountains Forming
Igneous Rock
1) CDN Shield
5) GLSLL2) AppalachianMTNS
“old eroded”
3) Western Cordillera4) Interior Plains“folding young”
oil
-Formation of Rocky Mountains Begins-Reptiles and Dinosaurs-1st birds and mammals
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Geologic History
• Cenozoic Era
• 65 million years to present (US!)
Mountains Forming
Igneous RockHeat
Volcanic Activity
Rockies 4) INTERIOR PLAINS 1) CANADIAN
SHIELD
3) APPALACHIAN
ATLANTIC OCEAN
2) GLSLL
CoastalMountains
5) WESTERN CORDILLERA
-Ice sheets cover most of NA-Continents take on present shape-Modern forms of life evolve
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Earth’s Interior
Crust- 8-64 km thick- cold & fragile- Granite and Basalt
Mantle- 1800 km thick- hot & molten- Magnesium and Silicon
Outer Core- 2000 km thick- 3 - 4000°C- liquid Nickel and Iron
Inner Core- 1400 km thick- 5 - 6000°C- solid Nickel and Iron
Air
Land
Water
LITHOSPHERE
HYDROSPHERE ATMOSPHERE
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Plate Tectonics - Continental Drift
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Plate Tectonics - Continental Drift
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Plate Tectonics - Continental Drift
Antarctica
THE CONTINENTS TODAY
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HMMMM
• Close examination of a globe often results in the observation that most of the continents seem to fit together like a puzzle: the west African coastline seems to snuggle nicely into the east coast of South America and the Caribbean sea; and a similar fit appears across the Pacific.
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PANGAEA
• 1912 Alfred Wegener (1880-1930)
• proposed that the continents were once compressed into a single large continent which he called Pangaea (meaning "all lands"),
• believed that Pangaea was intact until about 300 million years ago, when it began to break up and drift apart.
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FOUR MAIN PIECES OF EVIDENCE
• 1.
Wegener noted the jigsaw fit of South America and Africa, especially, but also elsewhere
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PROOF CONTINUED
2. He found fossils that were the same on both continents. After a certain period, the fossils begin to evolve differently on the different continents.
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3. He found that on both sides of the Atlantic, mountains were the same both in terms of age and structure.
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4. He found that ice sheets covered parts of Africa, India, Australia and South America 250 million years ago. How could this happen in places that are so warm today?
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PROBLEM
• Wegener's hypothesis of continental drift did NOT explain how the continents could drift across the earth's surface.
• ….thus, the theory of PLATE TECTONICS!NOT until the the 1960s
• Earth’s outer shell made up of 20 plates• They move over a weak layer of hot rock which flows like
slow-moving plastic• Unequal distribution of heat within the earth causes
convection currents to move the plates
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Plate Tectonics Map
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PLATE TECTONICS
• THERE ARE THREE BASIC PLATE MOVEMENTS
• 1. DIVERGENT
• where the plates move apart
• new magma wells up to the surface forming new crust
• the Mid-Atlantic ridge is a prime example.
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MID-ATLANTIC RIDGE
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2. CONVERGENT
• two plates come together
• one plate subducts (goes under) the other plate, creating a subduction zone
• the crust at the leading edge of the subducting plate melts back into the mantle
• 3 different types of convergent boundaries
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MID-OCEANIC CONVERGENCE
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B. Convergence Zone: Oceanic Crust and Continental Crust
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CONTINENTAL-CONTINENTAL
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Accumulated material melts as it goes down into the mantle.
Rises back up as liquid rock.Creates volcanoes and volcanic islands
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http://en.wikipedia.org/wiki/Mount_St._Helens
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3. TRANSFORM BOUNDARIES
• two plates slide past each other• this can create tremendous friction, which may be
eventually released in the form of violent earthquakes
• the San Andreas Fault is a transform boundary
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SAN ANDREAS FAULTCALIFORNIA
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Plate Tectonics Sliding
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Plate Tectonics Sliding
• Less than 3.5 Generally not felt, but recorded.• 3.5-5.4 Often felt, but rarely causes damage.• Under 6.0 At most slight damage to well-
designed buildings.• 6.1-6.9 Can be destructive in areas up to about
100 kilometers across.• 7.0-7.9 Major earthquake. Can cause serious
damage over larger areas.• 8 or greater Great earthquake. Can cause serious
damage in areas several hundred kilometers across.
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Tectonic setting of western British Columbia and Washington state. The oceanic Juan de Fuca plate is moving beneath the continental North America plate at a rate of about 4 cm/year. Earthquakes occur along parts of the boundary between the two plates.
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This map, which shows 20th-century earthquakes in red, illustrates how they cluster on the edges of the major tectonic plates (outlined in yellow).
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SUMMARY
Theory of continental drift and evidence to support it. (Pangea!)
Plate tectonics: how plates move (convection currents)Different movements of plates, geologic processes and
associated landformsDiverging: ridges/volcanoes
Converging: trenches, mountains, island arcsSubducting: same as above
Slipping/Transform: faults and earthquakesEarthquakes and Volcanoes: along major tectonic
plate boundaries