|A UH geoscientist’s recently published research refutes one of the most popular models for describing growth of the Himalayan mountains and has implications for global weather.
The findings of Michael Murphy, assistant professor of geosciences, appear in the Geological Society of America’s November 2007 issue of Geology. His article is titled “Isotopic characteristics of the Gurla Mandhata metamorphic core complex: Implications for the architecture of the Himalayan orogen.”
The Himalayas formed after India, which once was a separate continent, and Asia collided. Today a suture – envision stitches reconnecting skin after an operation – marks the site of this collision. The Tibetan Plateau, the Earth’s highest at approximately 20,000 feet, lies north of the suture and the Himalayan Range, which includes Mount Everest – the Earth’s highest mountain at approximately 29,000 feet.
Until now, most scientists thought rocks originating in the north beneath the Tibetan Plateau built the Himalayas. They envisioned that gravitational forces on the thick Tibetan crust squeezed these rocks south and upward, pushing up the mountains.
Murphy’s research, however, found that the rocks constituting the highest parts of the Himalayas actually originated in the lowlands of India and were moved north beneath the mountain range for more than 90 miles and then brought to the surface high along major faults. Some of these faults remain active today.
The Tibetan Plateau’s lofty elevation already tremendously impacts the world’s atmospheric circulation. If the popular growth model is true, Murphy said, the plateau will collapse and bring about dramatic changes in weather worldwide. If, on the other hand, his model is correct, Tibet will retain its current elevation and corresponding influence on the atmosphere.
Murphy used a caravan of yaks – as well as a team of Sherpas who lived in Nepal – to explore and sample rocks that were exposed in Western Tibet. He brought his collection back to various labs at UH, where they were analyzed to determine age and isotopic composition – a DNA fingerprint.
The results attest to how dynamic mountains are because of large horizontal movements of crustal blocks, where these blocks collide and where large and dangerous earthquakes can occur, Murphy said.