May 21, 2002
Professor finds in the Himalayas,
what goes up must come down
In a remarkable form of mountain metabolism,
the Earth's highest peaks seem to be washing away at the same
rate they are growing, says a geologist at California State
Geology professor Kevin Cornwell collected data from stream
drainages around Nanga Parbat, one of the highest peaks in
the Himalayas, as part of a 10-year effort in northern Pakistan
to study the concept of balance in the Earth's crust. Using
computer models, Cornwell and colleagues Richard Marston from
Oklahoma State University and Doug Norsby of the Kansas Department
of Public Works, found that the mountain surface is lowering
as much as six millimeters per year.
When they compared that lowering rate with the uplift rate
it turned out to be very similar. "The insight we get
is that the rate it is wearing away is pretty evenly balanced
with the rate it is going up," Cornwell says.
He has presented the findings at scientific meetings and at
the most recent Binghamton International Geomorphology Symposium.
Balance is an old concept, similar to icebergs in the ocean,
Cornwell says. "When you see a large rock mass, such
as a mountain, sticking out of the ground, there is even more
of it below the surface. The Himalayas are five miles high
which suggests a lot more under the surface."
The lofty laboratory of the Himalayas provides a unique look
at geological processes. The Himalayas are very young geologically,
and they are extreme, offering the chance to watch development
as it is happening, he says. While he cautions that he was
looking at relatively small amounts of data at select localities,
he notes conclusions can still be made. "We don't have
the luxury of watching these processes happen over time. Our
work is a snapshot of a brief piece of time that documents
the conditions that are going on now," he says. "We
then evaluate the conditions and extrapolate to the past."
His findings not only provide insight into how mountains are
formed, but offer glimpses into the causes and effects of
As fresh rock is "unroofed" and exposed to weathering
carbon dioxide is consumed by the atmosphere, which decreases
the atmosphere's ability to trap heat, Cornwell says. Over
the last two million years, the Earth's climates have been
cooler, perhaps because of the unroofing of the Himalayas.
Climate change can affect the precipitation in area seas as
well as the erosion potential in rivers and streams and how
much sediment they produce.
Cornwell began working in the Himalayas in 1991 as part of
his dissertation research. He spent the following year on
a Fulbright scholarship to University of Peshawar in Peshawar,
Pakistan. He returned for three months in 1997 on a National
Science Foundation-sponsored expedition to look at the amount
of sediment coming off the mountain through river actions.
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