Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Latest ice core may solve mystery of ancient volcanic eruptions

01.07.2002


A team of Ohio State University researchers has returned from an expedition in southeastern Alaska with the longest ice core ever drilled from a mountainous glacier.



The core measures 460 meters (1,509 feet) and is 150 meters (492 feet) longer than the previous longest core - a record of ice from the Guliya ice cap in western China that eventually relinquished a climate record stretching back 760,000 years - the oldest such record retrieved to date.

Until the new core is analyzed in detail, scientists won’t know if it exceeds the historic record provided by the Guliya core, but visible evidence in the new core itself suggests that the ice might reach back through several ice ages.


In April, Lonnie Thompson, professor of geological sciences at Ohio State, led this expedition - his 44th - to an ice cap that straddled the col, or saddle, between Mount Churchill and Mount Bona in the Wrangell-St. Elias National Park on the U.S.-Canadian border.

Mount Churchill is a 15,638-foot (4,766-meter) stratovolcano while Mount Bona is its 16,420-foot (5,005-meter) neighbor. The drill site on the col stood at an altitude of 14,500 feet (4,300 meters).

The core also revealed evidence that suggests geologists may have to rethink their understanding of the volcanic history of this region.

For years, scientists have believed that Mount Churchill was the source of a massive deposit of tephra, or volcanic ash, called the White River Ash that rose from at least two eruptions within the last 2000 years. That blast released between 25 and 30 cubic kilometers of ash across at least 340,000 square kilometers (131,275 square miles) in northwestern Canada and adjoining eastern Alaska.

Thompson’s team expected to find a layer of White River Ash several meters thick in the core since Mount Churchill, sitting adjacent to the drill site, is the believed source. They were shocked to discover that the ice core contained no such ash layer, making it unlikely for Churchill to have been the cause of the deposit.

"There simply was no ash there," Thompson said. "To me, that argues that this mountain couldn’t have been the source and that instead, Churchill may have served as a barrier to the ash that was coming from another source."

As if the absent ash layer wasn’t enough evidence, Thompson’s team found more obvious clues at their feet early in the expedition. On the ground surrounding the crater rim at the top of Mount Churchill, they found boulders and rocks composed of granodiorite, an igneous rock that is not produced by volcanic eruptions.

"These granodiorite pieces at the crater rim are sculpted by ice. These aren’t fragments -- they are smooth boulders. This kind of rock shouldn’t be present at the crater rim," Thompson said.
"If there had been an explosion at Mount Churchill large enough to have produced the White River Ash, it would have either blown the rocks away or buried them deeply."

The discovery of the granodiorite evidence at the crater rim may have been serendipitous. That area is normally covered under deep layers of snow most of the year and clears only for a few weeks at the end of winter. The Ohio State team just happened to reach the site when the ground was clear and the rocks were visible.

"A few weeks later and all of them would have been covered, he said. "That’s probably why no one has noticed this evidence before."

Even more surprising for expedition members was the discovery of several layers of pebbles of this same granodiorite in the bottom portion of the core. At a depth of 432 meters (1,417 feet), the team hit two layers of pebbles in the ice, separated by about seven centimeters (2.75 inches) of clean ice. They also encountered numerous pebble layers in the last two meters (6.5 feet) of the core.

While a precise explanation for these pebble layers must await a detailed analysis of the core, Thompson suggests that they may be evidence that massive ice sheets had overrun the mountain in the past.

During the last ice age, the eastern United States was covered by the Laurentide Ice Sheet while the American west was blanketed by the 4,000-foot-thick Cordilleran Ice Sheet. As these massive sheets moved, they scraped off stones from the underlying rock and transported them for thousands of miles.

Thompson believes both the stones at the crater rim and the pebble layers are remnants of those ice sheets. And the fact that they found multiple layers in the core suggests the area had been overrun by ice several times. Once the ice in the core is dated, they should have a better idea of when the layers were formed.

The Ohio State team returned with six cores altogether, all packed in 105 insulated boxes each containing six meters (19.6 feet) of ice. Along with the longest 460-meter core, they drilled a 116-meter (380.5-foot) core that will provide a complementary record to confirm the upper part of the longer core, and together both cores are expected to provide a climate history for this region reaching back thousands of years. They also drilled four 12-meter (39.3-foot) cores to help determine the snow accumulation rate at the site.

The Office of Polar Programs in the National Science Foundation supported the project.

Contact: Lonnie Thompson, (614) 292-6652; or thompson.3@osu.edu.
Written by Earle Holland, (614) 292-8384; Holland.8@osu.edu.

Lonnie Thompson | EurekAlert!
Further information:
http://www.nsf.gov/od/opp/
http://www.nsf.gov/

More articles from Earth Sciences:

nachricht Predicting eruptions using satellites and math
28.06.2017 | Frontiers

nachricht NASA sees quick development of Hurricane Dora
27.06.2017 | NASA/Goddard Space Flight Center

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Can we see monkeys from space? Emerging technologies to map biodiversity

An international team of scientists has proposed a new multi-disciplinary approach in which an array of new technologies will allow us to map biodiversity and the risks that wildlife is facing at the scale of whole landscapes. The findings are published in Nature Ecology and Evolution. This international research is led by the Kunming Institute of Zoology from China, University of East Anglia, University of Leicester and the Leibniz Institute for Zoo and Wildlife Research.

Using a combination of satellite and ground data, the team proposes that it is now possible to map biodiversity with an accuracy that has not been previously...

Im Focus: Climate satellite: Tracking methane with robust laser technology

Heatwaves in the Arctic, longer periods of vegetation in Europe, severe floods in West Africa – starting in 2021, scientists want to explore the emissions of the greenhouse gas methane with the German-French satellite MERLIN. This is made possible by a new robust laser system of the Fraunhofer Institute for Laser Technology ILT in Aachen, which achieves unprecedented measurement accuracy.

Methane is primarily the result of the decomposition of organic matter. The gas has a 25 times greater warming potential than carbon dioxide, but is not as...

Im Focus: How protons move through a fuel cell

Hydrogen is regarded as the energy source of the future: It is produced with solar power and can be used to generate heat and electricity in fuel cells. Empa researchers have now succeeded in decoding the movement of hydrogen ions in crystals – a key step towards more efficient energy conversion in the hydrogen industry of tomorrow.

As charge carriers, electrons and ions play the leading role in electrochemical energy storage devices and converters such as batteries and fuel cells. Proton...

Im Focus: A unique data centre for cosmological simulations

Scientists from the Excellence Cluster Universe at the Ludwig-Maximilians-Universität Munich have establised "Cosmowebportal", a unique data centre for cosmological simulations located at the Leibniz Supercomputing Centre (LRZ) of the Bavarian Academy of Sciences. The complete results of a series of large hydrodynamical cosmological simulations are available, with data volumes typically exceeding several hundred terabytes. Scientists worldwide can interactively explore these complex simulations via a web interface and directly access the results.

With current telescopes, scientists can observe our Universe’s galaxies and galaxy clusters and their distribution along an invisible cosmic web. From the...

Im Focus: Scientists develop molecular thermometer for contactless measurement using infrared light

Temperature measurements possible even on the smallest scale / Molecular ruby for use in material sciences, biology, and medicine

Chemists at Johannes Gutenberg University Mainz (JGU) in cooperation with researchers of the German Federal Institute for Materials Research and Testing (BAM)...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Plants are networkers

19.06.2017 | Event News

Digital Survival Training for Executives

13.06.2017 | Event News

Global Learning Council Summit 2017

13.06.2017 | Event News

 
Latest News

Supersensitive through quantum entanglement

28.06.2017 | Physics and Astronomy

X-ray photoelectron spectroscopy under real ambient pressure conditions

28.06.2017 | Physics and Astronomy

Mice provide insight into genetics of autism spectrum disorders

28.06.2017 | Health and Medicine

VideoLinks
B2B-VideoLinks
More VideoLinks >>>