As we drive up a series of switchbacks up to
Pang-la Pass (5200 m), we can see spectacular exposures of
faulted and folded forearc sediments from our precarious seats in
the rear of the truck (left).
We bounce up a rough road to Pangla Pass,
fording a river and speeding through muddy farm fields. We leave
the main highway and pass through a small Tibetan village (left).
As we drive up a series of switchbacks up to
Pang-la Pass (5200 m), we can see spectacular exposures of
faulted and folded forearc sediments from our precarious seats in
the rear of the truck (left).
The top of Pang-la Pass is marked by a cairn with a pole stuck in
its center from which hang strings of prayer flags. The base of
the cairn is piled with offerings of stones and bones. Nearby is
a low concrete monument with a plaque identifying the mountain
peaks, which protrude through a blanket of cloud to the south:
Makalu (8463 m), Lhotse (8516 m), Chomolungma (8848 m), and Cho
Oyu (8201 m). Beside it is a square post covered by aluminum
plates with the words "May Peace Prevail on Earth" written in
four languages: Tibetan, English, Japanese, and Chinese (left)
Someone has scratched over the Chinese and scribed "Free Tibet"
into the soft metal.
From Pangla Pass we can see the famous North Face and
Northeast Ridge of Mt. Everest (right), the site of the first
attempts to climb the Earth's tallest peak. On 8 June 1924, the
legendary British climber George Mallory ("Because it's there.")
and Andrew Irvine disappeared on the Northeast Ridge during their
bid to reach the summit. They were last spotted by Noel Odell,
the first geologist on Everest, above a rock outcropping called
the "Second Step", which is about 375 m beneath the summit. Odell
described them as "going strong," and debate continues to rage
whether they reached the summit only to die during their return.
It was not until 29 May 1953, that Sir Edmund Hillary and Tenzing
Norgay made the first generally recognized ascent. Mallory's body
was discovered by a 1999 NOVA-sponsored
expedition to the North Face of Everest. There's more about
Mt. Everest at http://www.peakware.com/encyclopedia/peaks/everest.htm
and http://www.nationalgeographic.com/everest.
The South Tibetan detachment fault crops out beneath the thick Ordovician carbonate beds that form Chomolungma's summit pyramid. This northward-dipping low-angle fault was only recognized in the past decade. It juxtaposes low-grade lower Paleozoic metasedimentary rocks and the high-grade metamorphic rocks of the Greater Himalayas. As the Himalayan Mountains grew, they became gravitationally unstable and their height was reduced by northward movement along listric extensional faults such as the South Tibetan Detachment. The detachment has been dated as Miocene (c. 20 Ma) and demonstrates that extension can occur simultaneously with compression in an orogenic belt.
