Storm delays arrival of helicopters
for three days
Beardmore Remote Camp
December 14, 2003
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| Molly Miller in Antarctica |
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In my last report, I mentioned that we were looking
forward to the arrival of helicopters and pilots on December 1.
However, a storm dumped more than 12 inches of snow on McMurdo
Station and then produced high winds that blew the snow into huge
drifts. This prevented the helicopters from flying out to us as
scheduled. McMurdo dug out in about three days and the helicopters
arrived on December 4.
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| When the helicopters did
make it to the Beardmore Remote Camp, 30
mph winds (plus an accident that damaged
one of the aircraft) interfered with the
research schedule because the helicopters
cannot take-off and land safely in high winds
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On Friday, December 5, one of the helicopters
dropped us off at an outcrop of rock about 25 miles away and we
had a glorious day examining 280 million year old lake deposits.
Unfortunately, one of the helicopters was damaged during a “hard
landing” related
to low atmospheric pressure at the elevation. The incident occurred
atop a high, 11,500-foot peak during an attempt to put up a radio
repeater. This shut down helicopter operations because the safety
regulations require that two aircraft must be operable in case
of an emergency. Another helicopter was flown from McMurdo the
next day, and a small plane delivered parts necessary to patch
the helo together so it could be flown back to McMurdo and repaired
properly.
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| Our camp on a windy day.
By the time this picture was taken, we had spent
several hours digging out four sleds. Each day
the snow drifts cover the entrances to our tents.
Simple tasks such as filling fuel tanks of Coleman
stoves and pulling food out of boxes are very
difficult . |
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The storm at McMurdo created a low pressure area that
was filled by air rushing from the high pressure over the polar
plateau. Sitting on glaciers in the mountains between the plateau
and the coast, we felt the brunt of this meteorological condition
in the form of sustained “katabatic” winds of about 30 miles per
hour. This made working outside unpleasant at best and tasks such
as writing field notes, taking photos or filling the Coleman stove
can quickly lead to frostbitten fingers. It has also wreaked havoc
on travel by helicopters. High winds here have kept most field
parties tent bound for at least two of the last five days. Nevertheless,
we had four good days of field work. A few of the highlights are
described below.
Animals lived in the bottom of river channels 240 million
years ago, but not 270 million years ago. We traveled by
helo to the top of a cliff of sandstone that was deposited in stream
channels. The slanted beds, called “cross-beds,” were deposited in
giant ripples on the bottom of the channels. It is obvious that animals
lived in the river sands because they left clear burrows. Because
the animals could not settle into the sediment when the water was
flowing rapidly, their very presence implies extended periods of
low stream flow. Information about the constancy of stream flow can
not be gleaned from physical characteristics so information from
the animals' burrows gives unique information about the ancient water
flow. We have also looked at river channel sandstones in slightly
older rocks and not found any burrows at all, even though the same
burrows, presumably made by the same animals, do occur in associated
sedimentary rocks deposited on the floodplains adjacent to the river
channels. We infer therefore, that there was a significant change
in the constancy of river flow between older (270 million year old)
and younger (20 million year old) river systems.
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| LEFT:
a cliff of Triassic sandstone deposited about 250
million years ago. MIDDLE:
Sandstone at top of cliff pictured on the left. The
large ripple marks indicate the material was deposited
at the bottom of a stream channel. RIGHT:
Animal burrows on the top surfaces of the sandstone
channels. |
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Very few animals lived in lake bottoms 290 million years
ago. Interbedded sandstone and shale were deposited in a
very large lake that covered an area possibly as large as the Great
Lakes combined. There are many thin layers of sandstone, each of
which was deposited by a flood or unusual event that interrupted
the typically quiet water conditions. Neither the sandstone interbeds
nor the shale are disturbed by animal burrows. We interpret this
to mean that the lake bottom was nearly devoid of animal life.
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| LEFT: A
cliff of interbedded shale and sandstone that was
deposited in a large lake about 290 million years
ago. RIGHT: Layers
of light-colored sandstone record influxes of sand
into the quiet water environment in which the shale
accumulated. The absence of burrows or other forms
of disruption indicates that few animals lived on
the lake bottom. |
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Some animals did live in smaller lakes and floodplains
270 million years ago, even though they were not abundant in the
stream channels. We looked at deposits of this age at one
of my favorite places, a high plateau I named “Top of the World” when
I first visited it 18 years ago. This time we discovered large stones
imbedded in much finer grained sediment. These “dropstones” are dropped
from floating ice as it melts, indicating that there was floating
ice of some type – either frozen river water or icebergs – and a
climate that was cold, at least seasonally. There are abundant animal
burrows. One looks just like a sine curve, a form so distinctive
that it is formally named Cochlichnus . It is found elsewhere
in the world in floodplain and lake deposits . At Top of
the World we discovered that it is made by a crustacean-like arthropod
rather than a worm-like animal: A worm could not have made the prod
marks we discovered on the outside of some of the burrows. We also
found symmetrical ripple marks that are formed by waves, indicating
that the floodplain lake in which they formed was very shallow.
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| TOP LEFT: The
large piece of white quartz is a dropstone. It was
embedded in ice and dropped into fine sediment when
the ice melted. It indicates the presence of ice
on at least a seasonal basis. TOP
RIGHT: The top of this plateau is accurately
described by my nickname “Top of the World.” BOTTOM
LEFT: Symmetrical ripple marks were produced
by waves in shallow water rather than by unidirectional
currents. BOTTOM
RIGHT: A
burrow made by a crustacean-like arthropod digging
just underneath the surface of the sediment. Prod
marks on some specimens found at “Top of the World” indicate
that this burrow form, which is common in fresh water
deposits worldwide, was produced by an arthropod
rather than a worm. |
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All in all, we have been able to piece together some important information
about the life and environment that existed between 240 million and
270 million years ago. We are enthusiastic about going to new areas
and seeing new rocks, but we are dependent on weather conditions.
The last week has demonstrated how dependent we are on good weather
and how difficult it is to carry on when the mercury is around zero
degrees Fahrenheit and the wind is blowing at 30 miles an hour. What
we learn intellectually helps us reconstruct the earth's past. What
we experience physically and emotionally demands that we respect
it.
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