hdwk mid ocean ridges –detected a long time ago molten material (go look! pillow lava!) magnetic...
TRANSCRIPT
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 RidgePingvellir, 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 activeeruptions
• 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 SubductionSubduction and makes the Deep Ocean TrenchesDeep Ocean Trenches
• Subduction and Deep Ocean Trenches
More Detail than you want! Subduction!
Some Vocab• 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 ___________.