SDAG Monthly Meeting
Wednesday, July 21, 2010 |
Location:
Catalina Room (southern end of MVCC)
Marina Village Conference Center
1936 Quivira Way
San Diego, CA 92109
Directions:
FROM INTERSTATE 5: Take the SEA WORLD DRIVE exit. From SEA WORLD DRIVE,
take WEST MISSION BAY DRIVE on your right. When you see the large green sign that
says QUIVIRA ROAD, get in the farthest left of the two left turn lanes. Turn left, go one
very short block and turn left again. Drive about one half mile and MARINA VILLAGE will
be on your right.
FROM INTERSTATE 8:Take the WEST MISSION BAY DRIVE exit to the right. You will
be on INGRAHAM STREET for a short distance from which you will take the next exit
marked WEST MISSION BAY DRIVE on your right. When you see the large green sign
that says QUIVIRA ROAD, get in the farthest left of the two left turn lanes. Turn left, go
one very short block and turn left again. Drive about one half mile and MARINA VILLAGE will be on your right.
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5:30pm -
Social hour |
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6:30pm -
Dinner
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Menu:
Hawaiian Buffet. Beverage station. Dessert. Cash bar.
Cost: $30.00, $12.00 for students, $5.00 discount for SDAG members and their guests if pre-registered by the deadline. $5 extra if you did not make a reservation.
Click the SDAG member checkbox on the reservation form if you are a member to receive a $5 discount. |
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Reservations:
Make your reservation online by clicking the button below
no later than noon, Monday, July 19th.
RESERVATIONS CANNOT BE ACCEPTED AFTER Monday at noon.
Late reservations/cancellations are preferred over walk-ins or no-shows.
Fees payable at the meeting or pre-pay with PayPal.
IF YOU DO NOT MAKE A RESERVATION, WE CANNOT GUARANTEE YOU A MEAL.
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If you are a current SDAG member and are not getting e-mail announcements,
make sure Todd has your correct e-mail address.
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7:00pm -
Program
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Speaker: Monte Marshall, Ph.D., Professor Emeritus of Geology and Geophysics, SDSU
"GEOLOGY AND WILDLIFE OF ANTARCTICA AND THE SOUTHERN OCEAN"
Abstract:
Antarctica is, in many ways, the most exotic of the six or seven continents. It has the highest
average elevation, the fastest winds, the lowest temperatures, and is the most remote of all
continents. Discovered only 200 years ago, it has no permanent residents, not even a single tree,
and is populated by only the most primitive of plants and only a few species of large animals,
including the very hardy scientists. Because it is centered almost exactly on the South Pole, it is so
cold that ninety eight percent of its surface is covered by ice - 7 million cubic miles of it, with an
average thickness of 6,500 feet. This is 90% of all the ice in the world, and 60% of the world's
fresh water. This, despite the fact that it is the driest continent in the world, with an annual
average precipitation of only 6 inches of liquid water equivalent.
The coastal outline of Antarctica looks like a ray. The part in the eastern hemisphere, called East
Antarctica, is a semi-circle with its coast lying on the Antarctic Circle and is the size of the United
States. East Antarctica is a fairly flat, pre-Cambrian shield, close to sea level, overlain in places by
flat-lying sedimentary rocks as old as Cambrian. The summit of the Antarctic ice cap is located
near the center of East Antarctica, about 600 miles east of the south pole, and has an elevation of
13,000 feet - only 3000 feet lower than the highest rocks on the continent! The tail of the ray lies
entirely in the western hemisphere, is called West Antarctica, and extends from the Ross Sea,
south of New Zealand, to the tip of the Antarctic Peninsula - just 600 miles south of Tierra del
Fuego, South America. Although also buried under thousands of feet of ice, radio echo ranging
shows that the bedrock has much more relief and West Antarctica appears to be an archipelago of
crustal blocks separated by basins that are up to 8,000' below sea level. These two halves of the
continent are separated by the 2000 miles long Trans-Antarctic Mountains (TAM), one of the
longest mountain ranges on earth. Much of the TAM is buried by ice and in places only the top few
hundred meters stick up above the ice. The highest mountain in the range is 14,800 feet above sea
level.
The oldest rocks in Antarctica are Archean, about 4 Ga, and are located on the coast of East
Antarctica, south of Africa. Like all continents, Antarctica grew by the addition of new crust in
various orogenies. By 1 Ga, all the crust of East Antarctica and some of West Antarctica had formed.
These orogenies occurred because the continent was moving and colliding with other
continents, forming clusters of continents called supercontinents that lasted for some time and
then rifted apart. East Antarctic, at least, along with Australia, South America, Africa, and India
formed the well-known supercontinent of Gondwana that lasted from about 500 Ma to 200Ma.
Between 300 and 200 Ma Gondwana joined a group of the northern continents of North America
and Eurasia (called Laurasia) to form the single supercontinent of Pangea. All the major land
masses of the earth formed in a giant circle around an ocean called Tethys. Apparently Pangea is
only the last of the single supercontinents. All the continents are currently thought to have been
together at 1 Ga, in a supercontinent called Rodinia that lasted from about 1.3 Ga to about 800 Ma.
Of great interest to us on the west coast of North America, is that either Australia or East
Antarctica lay to the west of us, that the ocean was thousands of miles west of Arizona, and that
our current Pacific coast formed when either of those continents rifted away from North America
at about 800 Ma! Paleomagnetic data show that our current West Coast actually ran E-W instead
of N-S and was near the equator at that time! The magnetic data show that East Antarctica
remained in tropical latitudes until the Silurian, at 450Ma, when it began drifting in a highly nonlinear
way to more southerly latitudes. It reached the South Pole in mid-Cretaceous at 100 Ma and
has remained there since. All the Gondwana continents, except South America, started rifting
away from Antarctica during the Cretaceous.
As was seen earlier, the polar position of Antarctica greatly affects its climate. But, its climate is
also affected by the great oceanic currents that circle the continent, especially the clockwise
current called the Antarctic Circumpolar Current. Only at 30 Ma was a 600 mile gateway/gap,
called the Drake Passage, created between the tip of South America and the Antarctic Peninsula,
allowing large currents to totally circle the continent. These currents, plus the complicated
mixture of relatively warm, salty water coming down from the north and colder, fresh water from
the melting of glacial ice and freezing of sea water to form the sea ice that surrounds the
continent much of the year, all set in motion oceanic and atmospheric currents that affect not only
the climate of Antarctica, but the whole world! Interestingly, the global greenhouse of the
Cretaceous and early Tertiary began to transition into the current global icehouse and the first
Antarctic ice sheet formed at about 30 Ma.
This gateway formed as the Andean subduction zone which formerly had extended down the west
coast of South America to the Antarctic Peninsula was severed at the present tip of South
America by the westward motion of South America as it separated from Africa. An almost 600
mile segment of the subduction zone was left 1000 miles east of Cape Horn to form the Scotia Arc
and Sandwich Islands, and fragments of the Andean crust were left strung out along the
transform fault. One of these Andean fragments now forms the largest, biologically richest, most
historic, and most lofty and scenic island in the Southern Ocean, South Georgia.
Monte's Bio: I was born in Mercy Hospital, San Diego, shortly after it was
established by Padre Junipero Serra. After being converted from
astronomy to geology by Baylor Brooks, I received my PhD from
Stanford under Allan Cox. My thesis was discovering what rocks
on the seafloor were causing the oceanic linear magnetic
anomalies--which had just proved the existence of continental
drift and seafloor spreading. After several years with the USGS
in Menlo Park, I loaded all my belongings (mostly books) in a 5-
foot U-Haul trailer and headed back down to San Diego to teach
and do research at SDSU. My main courses were Structural and
Petroleum Geology, Introductory Geophysics, and Paleomagnetism
and Plate Tectonics. After almost 30 years of teaching, with my mind and memory going, I
taught Rocks for Jocks in my last semesters! My research centered around making
detailed gravity surveys of metropolitan San Diego faults, and using paleomagnetism to
study crustal rotations in southern and Baja California.
As many of the older members of SDAG will testify, this is about my 10th talk to our
group - and my second one on Antarctica. But having just spent a month in Antarctic
waters, this one should be much more informative and maybe even more entertaining than
the last one! :>)
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Upcoming SDAG meetings - 2010
August 25: Rob Hawke: The La Jolla / Mt. Soledad Landslide Repairs
September 15: Candace Kohl: TBA
October: TBA
Meetings are usually scheduled for the 3rd Wednesday evening of the month. Meeting information on this website is normally updated the second week of the month.
If you have any information, announcements, ads or suggestions for an upcoming newsletter, please submit it to Todd Wirths, 2010 SDAG Secretary). Any news regarding upcoming events that may be of interest to the Association or news of your business can be submitted.
The submittal deadline for the next SDAG newsletter is the last Friday of the month.
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