Download Seafloor Spreading Notes - mrs. villarreal`s orange team science

Seafloor Spreading Notes
(#20)
Where we’ve been w/ EQ#2…
• EQ#2: What is convection and what
evidence is there of convection on the
surface of the Earth?
• Alfred Wegener
• Theory of Continental Drift
• Evidence for Continental Drift (Fossils,
landforms, climate)
• Theory rejected in early 1900’s
• In 1950’s, scientists discovered mid-ocean
ridge (ocean bottom was once thought flat)
Where we’re going w/ EQ#2…
• Magma erupting at mid-ocean ridge
creates new ocean floor & subduction at
plate boundaries destroys old ocean floor
• Seafloor spreading!
• Caused by convection currents in mantle
• We now know HOW the continents can
move
• Theory of Continental Drift revisited!
Wegener was a brilliant, brilliant man after
all!
Video Introduction to Sea
Floor Spreading
#20- Seafloor Spreading
• WHO: Discovered by Harry Hess- U.S. Geologist at
Princeton, Navy Reservist
• WHEN: 1950’s
• WHERE: Pacific Ocean
• WHAT:
– The process by which new ocean crust is formed
by the upwelling of magma at mid-ocean ridges.
– Cause: Convection currents in the mantle.
– Result: Existing/older ocean crust is pushed to the
side to make room for the new crust.
Seafloor spreading
OLDER
NEW
OLDER
EQUAL DISTANCE
FROM RIDGE =
SAME AGE
CONVEYOR BELT ANIMATION
Red=youngest rock
Blue=oldest rock
What happens to the OLD crust?
• Subduction: When the
edge of one crustal plate
is pushed underneath
another.
• This happens at the edge
of oceans, where denser
ocean crust is pushed
underneath less dense
continental crust. The
rock returns to the
mantle.
How can this move continents?
• If NEW ocean floor is produced FASTER
than old floor is subducted, the ocean floor
GROWS, which would push continents
APART.
• If OLD ocean floor is subducted FASTER
than new ocean floor is produced, the
ocean floor SHRINKS, which would “pull”
continents TOGETHER.
Please add the following to your
EQ#2 Vocabulary List (#19)
• 7. Seafloor Spreading: The process by which
new ocean crust is formed by the upwelling of
magma at mid-ocean ridges
• 8. Harry Hess: an American Geologist who
used SONAR to map the ocean floor in the
1950’s and discovered seafloor spreading
• 9. mid-ocean ridge• 10. Subduction: process by which ocean crust
sinks beneath a deep ocean trench and back
into the mantle at a convergent plate boundary
• Magnetization of the Ocean Floor
Animation
• http://www.absorblearning.com/media/atta
chment.action?quick=12n&att=2771