Download Sea- floor Spreading

Sea- floor Spreading
• The longest chain of mountains in the world
is the Mid-Ocean Ridge.
• Scientists have mapped the ocean floor and
mid-ocean ridge using S.O.N.A.R.
• The mid-ocean ridge extends into all of
Earth’s oceans.
• The Island of Iceland is part of the ridge that
rises above the surface in the Atlantic
Ocean.
• Down the middle of the ridge is an area
called the rift valley – It is almost twice as
deep as the Grand Canyon
Harry Hess
• Harry Hess examined maps of the midocean ridge and proposed that the ocean
floors move like conveyor belts, carrying
the continents along with them.
• This movement begins at the Mid- Ocean
Ridge.
• At the ridge, the molten material rises from
the mantle and erupts (much like a
volcano).
• The oldest rock is farthest from the center
of the ridge.
• Harry Hess first proposed the idea of SeaFloor Spreading.
Evidence for Sea-Floor
Spreading:
• Molten Material. The submersible
ALVIN was sent down to study the rift
valley.
Evidence
• Rock Sampling. The Glomar Challenger was
a drilling ship the gathered samples from the
ocean floor.
• The scientists determined the age- of the rocks
in the samples and found that the fartheraway from the ridge, the older the rocks were.
• The oldest rocks are about 4 million years old.
• The newer rocks were always in the center of
the ridges
Evidence
• Magnetic Stripes.
How does the
pattern of matching
stripes show
evidence of seafloor spreading?
How does the ocean floor keep
getting wider
• The ocean floor plunges
into deep under water
trenches.
• A deep ocean trench forms
where the oceanic crust
collides with continental
crust.
• Subduction is the process by
which the ocean floor sinks
beneath a deep-ocean trench
and back into the mantle.
FYI
• Most ocean trenches are found in the
Pacific Ocean.
• The deepest part of the ocean is the
Marianna’s Deep. It is located in the
Pacific Ocean
• The Pacific Ocean is shrinking, but it is
still the Largest ocean