Day 18 (Saturday, Sept. 23rd)
Cape Town With David Bell
Dave Bell, who we first met in Kimberley, met us during breakfast at our
hotel. He'd planned a fairly tight itinerary, which we were simply too slow to
keep. By the end of breakfast we were already an hour behind his schedule
thanks to our group's reluctance to leave nice, warm beds and a slight
miscommunication of the time we needed to be ready. We rushed through the
quiet streets, so different in the light and without a booming block party, to
the University.
When we arrived we found the campus deserted and went straight up to
look at the University's collection of deep mantle rocks. From a petrologic
standpoint it was an impressive collection that represented many different
pressures, temperatures, and other conditions within the mantle. We saw
beautifully polished peridotites, eclogites, kimberlites, and numerous other
rocks with huge crystals testifying of the length of time these portions of the
mantle spent at depth. Our next stop was the map room in the University. We
gorged ourselves on maps and posters, and found answers to many questions we'd
asked of the student presentations and hadn't been able to answer adequately
from observation or half-remembered information.
Sated, we left the University and drove to Table Mountain itself'. The
day was cool--much cooler than the previous day. Table Mountain was barely
visible through the thick, gray clouds we watched spinning around the mountain
top, dancing on the stiff breeze. We drove up as far as the road went,
watching the stratigraphy change as we climbed. The base of the mountain is
made up of the Cape Granite suite and Malmsbury shale. Above these deformed
and metamorphosed units lie the Cape and Karoo Supergroups, which are, in
contrast, almost completely flat. Our drive also took us past a beautifully
diverse array of native South African flowers that belong to the Cape Floral
Kingdom, also known of as Fynbos. One of the most spectacular is the
pincussion bush, which puts forth exotic, brightly-colored blooms the size
of a large man's fist.
We still had a schedule to keep so we drove quickly down the
mountain to
the Sea Point Contact. This point is an exposure of the contact between the
Malmsbury Shale and Cape Granite. The amazing thing about the contact is its
indistinct nature, and the fluid shapes and textures that are preserved in the
exposure. When the granite intruded it melted the overlying shales and mixed
with them, creating vortexes and long, inter-folded fingers of dark and light
rock. As the rocks cooled, these structures were preserved in the hardened
rock, and later exposed when the contact was uplifted and the overlying rock
eroded away.
At 11:30 we were expected to meet members of the Cape Town University
Geology department at the pier for a boat tour of the bay. Our group made it
just on time to find the boat wasn't quite ready for us, nor had everyone we
expected arrived. Soon we boarded, carrying coolers full of drinks and
sandwiches for the voyage.
We moved fairly slowly around the bay, allowing us to see many
dolorite
dikes and other structural features we'd missed when we were up closer. It's
amazing how stepping back can so often reveal details a close-up view
blinds us
to. As we moved away from the protection the tall rock walls around the bay
provided, winds and choppy seas buffeted us. Those of us wishing to remain
somewhat dry moved into the cabin, or at least to the rear of the ship. Some
few, including Antonin and some of our new friends from the University, stayed
near the front of the ship, and were soon sopping wet. We passed around a
small point and again found calmer waters, and saw swimming circles around us
numerous dark, streamlined shapes. A large group of seals played and
rested on
and around rocks perhaps a hundred meters away from the shore. For some
minutes we admired their playfulness and carefree natures. Soon, though, we
had to return to our own lives and cares.
Written by Kristine
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