Transcript 108-SeaFloor Spreading

HDWK
• Mid Ocean Ridges
– Detected a long time ago
• Molten Material (go look! Pillow Lava!)
• Magnetic Stripes
• Drilling Samples
• Subduction and Deep Ocean Trenches
Mid Ocean Ridges
Mid-Atlantic Ridge
Pingvellir, Iceland
• Iceland is
ripping apart –
but it gets filled
in with new
lava – so it gets
bigger!
Africa is tearing
apart too
How Convection helps Sea Floor
Spreading (traditional version)
Go Look for Volcanic Activity!
• Pillow lava from the Mid-Atlantic Ridge
• Shows active
eruptions
•
Sonar of
a volcano
& pillows
Magnetic
Stripes –
Reversals
Drilling the Sea Floor for Rock Ages
Glomar Challenger
• Drilling for Rocks (and used for other things!
but we’d have to kill you if we
told you what it was for
)
Can it Spread Forever??
• No Way, It has to go somewhere, and
usually it dives under a continent!
• Oceanic Crust is Denser than Continental
Crust – so it sinks under the continent.
• This process is called Subduction and
makes the Deep Ocean Trenches
• Subduction and
Deep Ocean
Trenches
More Detail than you want!
Subduction!
Some Vocab
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Plate
Convergent Plate Boundary
Divergent Plate Boundary
Transform Plate Boundary
Sea Floor Spreading
Magnetic Reversal
Rift Zone
Subduction
Island Arc
Hawaii is Special
• Hawaii is special, it is on the Pacific Plate,
but the hotspot under the Big Island
appears to have been there for 70+ million
years.
• The evidence is the chain of islands
stretching out to the NW from Hawaii to
Kure – and on along the Emperor
Seamount chain.
Kea and Loa
Tectonic Plates - names
• Most of the volcanoes are located on or
near ___________________
• _________ volcano is the only one in the
middle of a ___________.