Study Links Climate Change to Earthquakes

(CN) - Researchers from the University of Cincinnati say there is a "strong interaction" between climate change and the increased internal movements of mountains, including accelerated erosion and tectonic seismic activity.

Geologists led by the University of Cincinnati's Eva Enkelmann studied the St. Elias Mountains, a subgroup of the Pacific Coast Range located in southeastern Alaska, southwestern Yukon Territory and the northwestern tip of British Columbia in Canada.

Researchers have known that for millions of years global climate change has altered the structure and internal movement of mountain ranges, and that glaciers and erosion can change a mountain's local climate.

But the degree of this cause-and-effect relationship has not been clearly observed until Enkelmann and her team determined the way a mountain range moves and behaves topographically changes its local climate by redirecting wind and precipitation - which in turn accelerate erosion and tectonic seismic activity of the mountain range.

In the case of the St. Elias range, Enkelmann and her researchers found the northern portion of the range is very dry while the southern area receives a lot of precipitation that erodes the southern flanks of the range. As climate change influences the erosion, tectonic shifts occur according to the study.

Enkelmann next synthesized several data sets to show how a rapid exhumation occurred in the central part of the mountain range over 4 million to 2 million years ago. She found that the feedback process between erosion and internal tectonic shifting caused a mass of material to move up to the surface very rapidly.

While the earth was much warmer millions of years ago, glaciers still existed at high altitudes. But 2.6 million years ago, the Pliocene-Quaternary glaciation - "ice age" - period began and existing glaciers grew larger, froze solid and did not move.

Though technically still in the Pliocene-Quaternary glaciation period, glaciers today are wet-based, moving, and aggressively eroding material around and out. In the case of Enkelmann's study, the material eroded from the St. Elias Mountains is being pushed into the Gulf of Alaska. Meanwhile, internal tectonic plates continue to move toward Alaska, get pushed underneath and the glacial sediment is piling up above the Yakutat plate.

Enkelmann says the processes work against each other. Glaciers compete with the internal buildup, creating a feedback process that is "rapid and ferocious" - and likely what built the Himalayas, the European Alps and mountains in Taiwan. This, in an area that it is already seismically active: the second-largest earthquake ever recorded occurred in the area in 1964 - a 9.2 megathrust quake that killed at least 139 people and sent damaging tsunamis as far as California, Hawaii and Japan.

"In 1899, there were two big earthquakes in a row, an 8.1 and an 8.2 magnitude," Enkelmann said. "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."

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

Enkelmann published her findings in the journal Geophysical Research Letters, and also presented her findings at the annual Geological Society of America meeting earlier this month.

She is an assistant professor of geology at the University of Cincinnati.

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