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Science You could have been a mountain climber 12 million years ago
Science You could have been a mountain climber 12 million years ago | You could have been a mountain climber 12 million years ago |
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| by William Atkins | |
| Sunday, 27 April 2008 | |
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Science DiscussionsGerman geologist Andreas Mulch, a professor of tectonics and climate at the University of Hannover (Germany), lead the study that showed the central Sierra Nevada Mountains reached their present height about twelve million years ago. The Mulch expedition went from the Coast Ranges, near the Pacific Ocean, into the Central Valley, and on into the Ruby Mountains, in northeast Nevada, to analyze deposits of volcanic glass. The Ruby Mountains are within the Basin and Range region of Nevada and Utah. The discovery by Mulch and his team is important for the understanding by scientists of the geologic history of all mountain ranges throughout the world. It helps them to more accurately model global climates from early times on Earth to the present, and further on into our future. In fact, Mulch stated, “All the global climate models that are currently being used strongly rely on knowing the topography of the Earth." [Stanford: “Study: Mountains reached current elevation earlier than thought”] Mulch commented that scientists have shown with past studies that the Sierra Nevada Mountains and the Rocky Mountains in the western section of the United States contribute to weather and climate patterns as far away as the European continent. He stated, "If we did not have these mountains, we would completely change the climate on the North American continent, and even change mean annual temperatures in central Europe. That's why we need to have some idea of how mountains were distributed over planet Earth in order to run past climate models reliably." [Stanford] The Mulch team analyzed hydrogen isotopes (elements with the same atomic number) in water contained within volcanic glass (natural glass produced by the rapid cooling of molten lava ejected from volcanoes, cooled so fast that crystallization is not allowed to occur). This information provided them with the necessary data to conclude the timing of the uplift of the Sierra Nevada Mountains to their current peak altitude above the surface of Earth. Specifically, the ratio of hydrogen isotopes in the volcanic glass tells the researchers the changes that occured in the water vapor within air as it was contained over the Pacific Ocean and as it blew onto the North American continent over many millions of years of time in Earth’s past. Most of the rain fall (and continues to fall) on the windward side of the western U.S. mountains (on the western side as Pacific winds come in), so water falling to the ground contains heavier isotopes of hydrogen (as compared to lighter isotopes) than it does when it falls on the eastern slope of the mountains (the region that gets less rain overall). Generally, the windward side of these mountains receives more rainfall, making them greener with plants, trees, and other flora. On the other hand, the other side of the mountains usually receives much less rain, and often such areas are found to be desert or semi-desert climates. The difference in rainfall amounts and the resulting landscapes between the two sides are often called the “rain shadow,” or any area of land on Earth that receives small amounts of precipitation due to the effect of a barrier (such as a mountain range), which causes the winds to drop their moisture content before reaching that land mass, which usually has desert-like conditions. And, the higher in elevation the mountain barriers have reached, the more difference in the two regions; thus, producing a more distinct "rain shadow" effect between the dry and wet sides of the barrier. Thus, according to the April 23, 2008 Stanford report, “By determining the ratio of heavier to lighter hydrogen isotopes preserved in volcanic glass and comparing it with today's topography and rainwater, researchers can estimate the elevation of the mountains at the time the ancient water crossed them.” How can volcanic glass preserve water? Please read on. |
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