Skip to main content

Climate change is moving mountains


Terminus of the Hubbard Glacier at Resurrection Bay. The ice front is about 300 feet high.
Credit: provided by UC's Eva Enkelmann.


Moving Mountains


"To understanding how mountain structures evolve through geologic time is no quick task because we are talking millions of years," says Enkelmann. "There are two primary processes that result in the building and eroding of mountains and those processes are interacting."



Looking at the St. Elias Mountains in particular, Enkelmann notes how dry it is in the northern part of the mountain range. But the precipitation is very high in the southern area, resulting in more erosion and material coming off the southern flanks. So as the climate change influences the erosion, that can produce a shift in the tectonics. This has been suggested in earlier studies based on numerical and analytical models, however, it had not yet been shown to have occurred over geologic times in the real world.



Enkelmann synthesized several different data sets to show how a rapid exhumation occurred in the central part of the mountain range over four to two million years ago. This feedback process between erosion and internal tectonic shifting resulted in a mass of material moving up toward the surface very rapidly.



Enkelmann's model suggests that global climate shifts triggered a change in the rheology -- the way material behaves.


While Earth was much warmer millions of years ago, glaciers still existed in the high altitudes. However, 2.6 million years ago Earth experienced a shift to a colder climate and glaciation intensified. Existing glaciers grew larger, froze solid, covered the area and did not move.

Enkelmann says the glaciers today are wet-based and are moving, very aggressively eroding material around and out, and in the case of her observation, into the Gulf of Alaska. The tectonic forces (internal plates moving toward one another) continue to move toward Alaska, get pushed underneath and the sediment on top is piling up above the Yakutat plate.

Shake, Rattle and Roll


Adding to the already complex effects of climate change, these processes essentially work against each other.



The movement of glaciers can compete with the internal buildup and develop a feedback process that is very rapid and ferocious. Scientists have suggested that the Himalayas, European Alps and mountains in Taiwan were caused by the same competing reactions as those Enkelmann has observed in southeastern Alaska.



In Enkelmann's observation, the climate-driven erosion can influence the tectonics and change the motion of the rocks in that area. This makes studying the St. Elias Mountain Range particularly ideal because this area is very active tectonically, with strong glacial erosion. As an example, she cites the Great Alaskan Earthquake of 1964 -- the world's second largest earthquake recorded to date -- that also resulted in a tsunami.



"In 1899, there were two big earthquakes in a row, an 8.1 and an 8.2 magnitude, says Enkelmann pointing to a photo of the resulting shoreline lift that still stands today. "These earthquakes resulted in up to 14 meters of co-seismic uplift on the shore, so the shoreline basically popped up 14 meters (45 feet) and it happened immediately.


"Our biggest concern today is the continued potential for earthquakes that can also result in tsunamis," says Enkelmann.

Enkelmann appreciates the challenge of collecting samples here because this range has the highest peaks of any coastal mountain range and is only 20 kilometers from the Pacific Ocean, but she points out that it is a tough area to study because of the big ice sheets.

"So as geologists, we go to the area and take samples and do measurements in the field on the mountain ranges that stick out," says Enkelmann. "One approach is to sample the material that comes out of the glaciers that has transported the eroded sediment and analyze that sediment.

"By going to all of these individual glaciers, we can get a much better understanding of what has happened and what was moved on the entire mountain range."


Published research by University of Cincinnati's Eva Enkelmann, assistant professor of geology in McMicken College of Arts & Sciences shows clear relationship between climate-influenced erosion and long term exhumation and movement of rock, particularly in the southern portion of the North American Pacific coastal St. Elias Mountain Range.
Video created by Melanie Schefft/UC E-News. Photos by Eva Enkelmann.



Reference:

Eva Enkelmann, Peter O. Koons, Terry L. Pavlis, Bernard Hallet, Adam Barker, Julie Elliott, John I. Garver, Sean P. S. Gulick, Rachel M. Headley, Gary L. Pavlis, Kenneth D. Ridgway, Natalia Ruppert, Harm J. A. Van Avendonk. Cooperation among tectonic and surface processes in the St. Elias Range, Earth's highest coastal mountains. Geophysical Research Letters, 2015; 42 (14): 5838.



Note: The above post is reprinted from materials provided by University of Cincinnati.

Comments

Post a Comment

Popular posts from this blog

The world’s rarest minerals

Nevadaite (Cu2+,Al,V3+)6[Al8(PO4)8F8](OH)2·22H2O) is a category 1 and 2 rarity–formed from the scarce elements vanadium and copper under very restricted environmental conditions. The crystals are colorful but microscopic, and only known from two localities–Eureka County, Nevada, and a copper mine in Kyrgyzstan. Credit: Robert Downs, University of Arizona. Scientists have inventoried and categorized all of Earth’s rare mineral species described to date, each sampled from five or fewer sites around the globe. Individually, several of the species have a known supply worldwide smaller than a sugar cube. These 2,550 minerals are far more rare than pricey diamonds and gems usually presented as tokens of love. But while their rarity would logically make them the most precious of minerals, many would not work in a Valentine’s Day ring setting. Several are prone to melt, evaporate or dehydrate. And a few, vampire-like, gradually decompose on exposure to sunlight. Their greatest ...
1 comment
Read more

You Can't Get Entangled Without a Wormhole

You Can't Get Entangled Without a Wormhole:-Quantum entanglement is one of the more bizarre theories to come out of the study of quantum mechanics -- so strange, in fact, that Albert Einstein famously referred to it as "spooky action at a distance." Essentially, entanglement involves two particles, each occupying multiple states at once -- a condition referred to as superposition. For example, both particles may simultaneously spin clockwise and counterclockwise. But  neither has a definite state until one is measured, causing the other particle to instantly assume a corresponding state. The resulting correlations between the particles are preserved, even if they reside on opposite ends of the universe. But what enables particles to communicate instantaneously -- and seemingly faster than the speed of light -- over such vast distances? Earlier this year, physicists proposed an answer in the form of "wormholes," or gravitational tunnels. The group showed th...
Post a Comment
Read more

Scientists Are Mapping The World's Largest Volcano

New 3-D maps reveal some of the features of the Pacific's Tamu Massif, including this long cliff. Imaging courtesy of Schmidt Ocean Institute After 36 days of battling sharks that kept biting their equipment, scientists have returned from the remote Pacific Ocean with a new way of looking at the world’s largest—and possibly most mysterious—volcano, Tamu Massif. The team has begun making 3-D maps that offer the clearest look yet at the underwater mountain, which covers an area the size of New Mexico. In the coming months, the maps will be refined and the data analyzed, with the ultimate goal of figuring out how the mountain was formed. It's possible that the western edge of Tamu Massif is actually a separate mountain that formed at a different time, says William Sager, a geologist at the University of Houston who led the expedition. That would explain some differences between the western part of the mountain and the main body.  The team also found that the massi...
Post a Comment
Read more