Sea Floor Spreading The Mid-ocean Ridge So do dolphins

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Sea Floor Spreading

• The Mid-ocean Ridge

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• Vocabulary
• Sonar
• Sea-floor spreading
• Deep-ocean trench
• Subduction
• Mid-ocean ridge

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60 years ago, in the 1950s, Sonar was invented.
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Bats use it!
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So do dolphins!
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So does this guy!
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Sonar brought Wegners theory back to life!
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Sonar made it possible for us to observe the
ocean floor.
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Soon, scientists observed a large mountain chain
running down the center of the Atlantic ocean.
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They quickly found that the ridge ran around the
world!
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Harry Hess American Geologist
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No! Harry Hess, not Harry Potter!
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Sea-Floor Spreading

• Harry Hess

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Pillow Lava forms when magma cools in water. This
is evidence of volcanic activity!
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This shows you the age of the sea floor. The red
areas are new rocks and the blue areas are the
oldest oceanic rock.
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Iceland is spreading open on the Mid-Atlantic
Ridge!
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Can you see where the Mid-Atlantic Ridge bisects
Iceland? This is a rift valley!
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Sea Floor Spreading

• Sonar
• Mid-Ocean Ridge
• ocean is spreading open!!!
• pillow lava
• magnetic stripes
• Drilling rock samples

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If new crust is being added to Earths surface,
is Earth getting bigger?
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Subduction is a process where the ocean floor
sinks back into the mantle at a deep ocean trench.
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