Download Seafloor Spreading PPT

Name:
Date:
Period:
Type of Evidence
Physical Proof Through OBSERVATIONS
Parsons, 2009
PROBLEM
In 1947, seismologists on the U.S. research
ship Atlantis found that the sediment layer
on the floor of the Atlantic was much thinner
than originally thought.
PRIOR BELIEF IN 1947
Scientists had previously believed that the oceans
have existed for about 4.5 billion years, so therefore
the sediment layer should have been very thick.
Copy and complete the following “If…then” statement
based on what scientists believed in 1947:
If Earth’s rocks have been proven to be about 4.5
billion years old, then _______________________.
In the 1960’s, technology allowed scientists to take
pictures with the help of a submersible called ALVIN.
It could withstand crushing pressures up to 4 kilometers.
Scientists discovered….
…there are lines of cracks on Earth’s ocean floor that
resembles the shape of lines on a baseball!
Please open your textbook
and read 199-201.
Type of Evidence
“NEW” Rocks
What rock is most
abundantly formed
from an a crack in
an ocean?
Physical Proof Through OBSERVATIONS
In the 1960’s, scientists
rock
discovered that new _____
was being formed at the
bottom of Earth’s oceans
through cracks
Scientists discovered strange rocks
shaped like pillows
because the molten material is squeezed
through the crack like from a tube of
toothpaste!
Type of Evidence
Magnetic
Stripes
We can test
magnetic directions
because opposites
attract!
Physical Proof Through OBSERVATIONS
We know that Earth
magnet
behaves like a _______
with a north pole and a
south pole.
Scientists believe that
every 780,000 years, the
North and South poles
REVERSE!
Let’s see how the ocean floor
spreads…
Seafloor Spreading Lab
Type of Evidence
Drilling
Samples
Why does rock get
‘older’ as it gets
farther from a ridge?
Physical Proof Through OBSERVATIONS
In 1968, the Glomar
Challenger, a drilling ship
was designed to drill in the
ocean floor.
We discovered that the
newer rock is located
closest to the mid-ocean
________
ridge.
Glomar Challenger
Lastly, let’s discuss
SUBDUCTION…
Trust me!
This is very interesting!
Even though the Pacific ocean
covers almost 1/3 of Earth, it is
SHRINKING!
HUH?
Subduction: When two plates come
together (CONVERGE), one can sink
under the other into the mantle.
How does
that happen?
So, let’s review…
RESOURCES
nasa.org
noaa.gov
usgs.gov
ucmp.berkeley.edu
Holt Earth Science, 2008
Prentice Hall Earth
Science, 2002