Researchers for the first time have attempted to measure all the material leaving and entering a mountain range over more than a million years and discovered that erosion caused by glaciation during ice ages can, in the right circumstances, wear down mountains faster than plate tectonics can build them.
The international study conducted by the Integrated Ocean Drilling Program and led by scientists from the University of Florida, The University of Texas at Austin and Oregon State University, adds insight into a longstanding debate about the balance of climate and tectonic forces that influence mountain building. It is published today in the Proceedings of the National Academy of Sciences.
Researchers studied the St. Elias Mountains on the Alaskan coast and found that erosion accelerated sharply about 1 million years ago when global climate cooling triggered stronger and more persistent ice ages than times past.
"Humans often see mountain ranges as static, unyielding parts of the landscape,” said co-chief scientist John Jaeger, an associate professor of geology at the University of Florida. “But our work has shown that they are actively evolving along with, and responding to, Earth's climate, which just shows how truly dynamic and coupled this planet is."
The study, conducted by a team of scientists from 10 countries, culminated more than a decade of field work. Researchers first used seismic equipment to image and map a huge fan of sediment in the deep sea in the Gulf of Alaska caused by erosion of the nearby mountains and took short sediment cores to understand the modern system.
They then collected and dated almost 4 kilometers of sediment from the floor of the gulf and the Alaskan continental shelf, revealing millions of years of geologic history.
“It turned out most [sediments] were younger than we anticipated, and most rates (of sediment production and thus erosion) were higher than we anticipated,” said lead author and co-chief scientist Sean Gulick of the University of Texas Institute for Geophysics, a unit of the Jackson School of Geosciences.
“Since the big climate change during the mid-Pleistocene transition when we switched from short (about 40,000-year) ice ages to super-long (about 100,000-year) ice ages, erosion became much greater... In fact, there was more erosion than tectonics has replaced.”
“We were pleasantly surprised by how well we could establish ages of the sediment sequences as we were drilling, and the composition of the sediment gave clear evidence of when the glaciation started and then expanded, in synch with global climate trends over the past several million years,” said co-author Alan Mix of Oregon State University. “Only by drilling the sea floor where the sediment accumulates could we see these details.”
Mountain ranges form when tectonic plates thrust into one another over millions of years and scrunch up the Earth’s outer crust. But even as mountains are built by these titanic forces, other agents -- some combination of tectonic and climate processes -- work to remove the accumulating crust.
Since the mid-Pleistocene, erosion rates have continued to beat tectonic inputs by 50 to 80 percent, demonstrating that climatic processes, such as the movement of glaciers, can outstrip mountain building over a span of a million years. The findings highlight the pivotal role climate fluctuations play in shaping Earth’s landforms.
The study was funded by the U.S. National Science Foundation and the Integrated Ocean Drilling Program.
Writer: Steve Orlando, 352-846-3903
Source: John Jaeger, 352-846-1381, firstname.lastname@example.org
Steve Orlando | newswise
New research calculates capacity of North American forests to sequester carbon
16.07.2018 | University of California - Santa Cruz
Scientists discover Earth's youngest banded iron formation in western China
12.07.2018 | University of Alberta
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
13.07.2018 | Event News
12.07.2018 | Event News
03.07.2018 | Event News
18.07.2018 | Materials Sciences
18.07.2018 | Life Sciences
18.07.2018 | Health and Medicine