~ Plate Tectonics Theory ~
The Earth's CRUST is cracked into 7 Major and 7+ Minor Plates
Click here: List of Tectonic Plates / Bill Nye Crust / Crust Song
MAJOR PLATES |
MINOR PLATES |
1. Pacific
2. North American
3. South American
4. African
5. Eurasian
6. Indian-Australian
7. Antarctic |
1. Juan De Fuca
2. Cocos
3. Nazca
4. Caribbean
5. Scotia
6. Arabian
7. Philippine |
Plate Tectonics / Tectonic Plates
Earth Activities / Best Map of Tectonic Plates
Above: Map Showing Plate Boundaries (black)
Above: Map Showing Location of Plate Boundaries (yellow)
( Note: The African Plate is missing from the above map. )
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What Alfred Wegener didn't know...
Plate Tectonics: Why do plates move?
Answer: Plates move due to Sea-Floor Spreading,
and because of Convection Currents in the mantle.
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Advances in SONAR or SUBMARINE technology in the 1960's
allowed scientists to understand what was happenig on the Ocean Floor.
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~ Sea Floor Spreading ~
Above: The Mid-Atlantic Ridge
Above: The Global Mid-Oceanic Ridge System
Click here: Harry Hammond Hess // SFS with Bill Nye
Animation Above: How sonar works.
Sound waves bounce off the ocean floor,
and then back to the sonar recording device on the ship.
Ocean Floor Map
Question: Why is the Sea Floor spreading?
Answer: Convection Currents in the Mantle are causing Oceanic Crust to separate.
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The Sea Floor is Diverging (moving apart)
at the Mid-Ocean Ridges:
A Mid-Ocean Ridge System
~ What is a Subduction Zone? ~
Subduction:
Subduction is the process by which one plate is pushed down beneath another plate.
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FYI: Deep Sea Trenches and Volcanoes form at Subduction Zones.
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~ Magnetic Pole Reversal Stripes on the Ocean Floor ~
(Proof of Sea Floor Spreading)
Sea Floor Spreading
Magnetic Pole Reversals
Like all magnets, Earth's magnetic field has two opposing regions, or poles, positioned approximately near geographical North and South Poles. During a period of normal polarity the region of attraction corresponds with the North Pole.
Today, a compass needle, like other magnetic materials, aligns itself parallel to the magnetizing force and points to the North Pole. During a period of reversed polarity, the region of attraction would change to the South Pole and the needle of a compass would point south.
Studies of the magnetism retained in rocks at the time of their formation (like small compasses frozen in time) have shown that the polarity of the Earth's magnetic field has reversed repeatedly throughout geological time.
The reason for polar reversals is not known. Although the average time between reversals over the last 10 million years has been 250,000 years, the rate of reversal has changed continuously over geological time. The most recent reversal was 780,000 years ago; scientists have no way of predicting when the next reversal will occur. The entire reversal process probably takes a few thousand years to complete.
Learn more: Magnetic Flip-Flop / Historical Chart
And more: Nova - Magnetic Storm
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Click here: Sea Floor Spreading Video
Magnetic Pole Reversals
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~ Types of Plate Boundaries ~
A. Divergent (moves apart/spreads apart)
B. Convergent (moves together/collides)
C. Transform (moves in opposite directions, horizontally)
Animations of Plate Boundaries
Pre-Plate Tectonics...
How do mountains form?
The (False) Wrinkled Apple Theory of Mountain Formation
The Earth is shrinking and wrinkling from exposure to the sun...yeah...that's it.
...just like a prune wrinkling and shriveling into a prune.
...or grapes shrinking and shriveling into raisins.
(Mountains actually form due to continental collisions and by folding due to pressure.)
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Converging Continental Plates:
Mountain Range Formation
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Convergence of an Oceanic and Continental Plate:
Subduction Zone with Trench and Volcano
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Diverging Oceanic Plates:
Mid-Ocean Ridge (shown above)
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CONVERGENT PLATES:
Above: Continent - Continent Colllision
Result: Formation of a Mountain Range
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CONVERGENT PLATES:
Above: Ocean - Continent Collision
Result: Formation of a Trench and a Volcanic Arc
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CONVERGENT PLATES:
Above: Ocean - Ocean Collision
Result: Formation of a Trench and an Island Arc
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Below: Location of Plate Boundaries in Western USA.
NOTE: The San Andreas Fault is a Transform Fault.
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~ The Pacific Ring of Fire ~
The oceanic crust of the Pacific Plate subducts underneath surrounding continental plates,
causing a circular ring of earthquakes and volcanoes on its borders.
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~ Iceland and the Mid-Atlantic Ridge ~
All Mid-Ocean Ridge Systems are DIVERGENT plate boundries.
Above: Location of Mid-Atlantic Ridge through Iceland
Icelancic Adventure Tour
Iceland and the Mid-Atlantic Ridge
Above: The Ice of Iceland
Above and Below: Iceland featuring exposed Mid-Atlantic Ridge
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~ The Himalayas and Continental Plate Collision ~
The Indian Plate collided with Eurasian Plate...
...approximately 20 million years ago.
Above: Collision of India with Eurasia (Formation of the Himalayas)
Animation: Collision of Indian Subcontintent with Asia
Above: Chomolungma / Mount Everest (29,035 ft. above sea level)
Below: North Face of Mt. Everest featuring the "Yellow Band"
Mount Everest / Everest Map / Hilary and Norgay / Lost on Everest
Himalayan Geology / Highest Fossils / Everest Facts / Panorama
Above: Sir George Everest
Himalayas by Kaiter
World Mountain Ranges
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~ Hydrothermal Sea Vents ~
Above: Hydrothermal Sea Vent
SEA VENT:
A localized series of small breaks in the interior of an oceanic plate,
through which hot gases erupt.
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Below: Hydrothermal Sea Vent
Pompeii Worm / Sea Vents / Monsters of the Sea
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~ The Hawaiian Hot Spot ~
HOT SPOT:
a large, stationary plume of super hot magma
that breaks through the tectonic plate moving over it,
causing continual volcanic activity.
Yellowstone Hot Spot
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Hawaiian Hot Spot Animation
Future Hawaiian Vacation Hot Spot...Loihi
Above & Below: Hawaiian Hot Spot
Hot Spot / Hawaiian Hot Spot
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~ Rift Valley Hot Spots ~
NOTE: Some scientists believe that when HOT SPOTS link up,
then RIFT VALLEYS are formed,
causing PLATES to SEPARATE as if being unzipped,
like what happened when PANGAEA split apart.
The African Great Rift Valley Hot Spot
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