Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Pre-eruption earthquakes offer clues to volcano forecasters

17.12.2009
Like an angry dog, a volcano growls before it bites, shaking the ground and getting "noisy" before erupting.

This activity gives scientists an opportunity to study the tumult beneath a volcano and may help them improve the accuracy of eruption forecasts, according to Emily Brodsky, an associate professor of Earth and planetary sciences at the University of California, Santa Cruz.

Brodsky will present recent findings on pre-eruption earthquakes on Wednesday, December 16, at the fall meeting of the American Geophysical Union in San Francisco.

Each volcano has its own personality. Some rumble consistently, while others stop and start. Some rumble and erupt the same day, while others take months, and some never do erupt. Brodsky is trying to find the rules behind these personalities.

"Volcanoes almost always make some noise before they erupt, but they don't erupt every time they make noise," she said. "One of the big challenges of a volcano observatory is how to handle all the false alarms."

Brodsky and Luigi Passarelli, a visiting graduate student from the University of Bologna, compiled data on the length of pre-eruption earthquakes, time between eruptions, and the silica content of lava from 54 volcanic eruptions over a 60-year span. They found that the length of a volcano's "run-up"--the time between the onset of earthquakes and an eruption--increases the longer a volcano has been dormant or "in repose." Furthermore, the underlying magma is more viscous or gummy in volcanoes with long run-up and repose times.

Scientists can use these relationships to estimate how soon a rumbling volcano might erupt. A volcano with frequent eruptions over time, for instance, provides little warning before it blows. The findings can also help scientists decide how long they should stay on alert after a volcano starts rumbling.

"You can say, 'My volcano is acting up today, so I'd better issue an alert and keep that alert open for 100 days or 10 days, based on what I think the chemistry of the system is,' " Brodsky said.

Volcano observers are well-versed in the peculiarities of their systems and often issue alerts to match, according to Brodsky. But this study is the first to take those observations and stretch them across all volcanoes, she said.

"The innovation of this study is trying to stitch together those empirical rules with the underlying physics and find some sort of generality," Brodsky said.

The underlying physics all lead back to magma, she said. When the pressure in a chamber builds high enough, the magma pushes its way to the volcano's mouth and erupts. The speed of this ascent depends on how viscous the magma is, which depends in turn on the amount of silica in the magma. The less silica, the runnier the magma. The runnier the magma, the quicker the volcanic chamber fills and the quicker it will spew, according to Brodsky.

The path from chamber to surface isn't easy for magma as it forces its way up through the crust. The jostling of subsurface rock causes pre-eruption tremors, which oscillate in length and severity based on how freely the magma can move.

"If the magma's very sticky, then it takes a long time both to recharge the chamber and to push its way to the surface," Brodsky said. "It extends the length of precursory activity."

Thick magma is the culprit behind the world's most explosive eruptions, because it traps gas and builds pressure like a keg, she said. Mount St. Helens is an example of a volcano fed by viscous magma.

Brodsky and Passarelli diagrammed the dynamics of magma flow using a simple analytical model of fluids moving through channels. The next step, Brodsky said, is to test the accuracy of their predictions on future eruptions.

Volcanoes are messy systems, however, with wildly varying structures and mineral ingredients. Observatories will likely have to tweak their predictions based on the unique characteristics of each system, she said.

In addition to Brodsky and Passarelli, Stephanie Prejean of the U.S. Geological Survey's Alaska Volcano Observatory contributed to the study that Brodsky will present at the AGU meeting.

Tim Stephens | EurekAlert!
Further information:
http://www.ucsc.edu

More articles from Earth Sciences:

nachricht Climate satellite: Tracking methane with robust laser technology
22.06.2017 | Fraunhofer-Gesellschaft

nachricht How reliable are shells as climate archives?
21.06.2017 | Leibniz-Zentrum für Marine Tropenforschung (ZMT)

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

Study shines light on brain cells that coordinate movement

26.06.2017 | Life Sciences

Smooth propagation of spin waves using gold

26.06.2017 | Physics and Astronomy

Switchable DNA mini-machines store information

26.06.2017 | Information Technology

VideoLinks
B2B-VideoLinks
More VideoLinks >>>