Transcript Plate Tectonics II

Friday's Geology Seminar:
Dr. Maureen Raymo
Research Professor, Boston University
"
"
1:00 p.m., Mudd 218
Light
refreshments
beforehand!
Plate Tectonics - Part II
(What ELSE can happen??)
I. The Appalachian Mountains are a product of
ancient subduction followed by collisions.
The giant folds in the rocks that
are so visible in the satellite
images are also readily available
from the window of a plane.
Other bits and
pieces of land islands and the
like - can also get
caught up in the
convergent plate
process.
This is what creates
what are now
recognized as
accreted terranes,
(originally called
"suspect terranes").
IMAGINE ...
what the geologic
situation would
ultimately look
like if Australia
were to be moving
to the NW,
pushing
everything from
New Guinea to
Sumatra into the
SE margin of the
Asian mainland...
What might the future hold???
MAYBE!!!!!
The BASIN AND
RANGE Province of
the western U.S.,
including all of Nevada
and parts of
surrounding states,
MAY be an area where
North America is
trying to split apart!
The mantle upwelling
beneath the East
Pacific Rise doesn't
just cease to exist in
between the Gulf of
California and the
Gorda Ridge!
This region has been broadly UPLIFTED by tectonic
forces pushing up from beneath.
The plains of Wyoming are very
flat, but 7000-8000 feet (2100
to 2400 m) above sea level.
The Grand Canyon catches
the eye for its tremendous
depth, but the North Rim is
also over 8000 feet (2400 m)
above sea level! Note how
FLAT the upland surface is!
In most other areas, the rocks
have fractured in normal
faults, which are produced
only by stretching a brittle
material - pulling it apart.
On a larger scale, this
then shows up in repeated
patterns of block faulting
This produces a series of downdropped
blocks called GRABENS in between the
uplifted HORSTS. (The grabens are the
valleys, the mountain ranges the horsts.)
The Humboldt Range of
Nevada, for example, is part
of this system.
What COULD happen as an alternative scenario,
as a result of this process in the western U.S.?
It's thinking about
scenarios like this that
has led some geologists to
call geophysics
"The realm of conjecture,
speculation and dreams."
Coming
Tuesday:
Producing Islands by Rifting