Earthquakes can release methane from the seabed, a new study has found.
Researchers from University of Bremen and their colleagues found a new source of methane- an earthquake that occurred in Pakistan about 70 years ago. They found that this event fractured the sea-bed and released methane in the atmosphere. Researchers said that policy-makers on climate change need to consider the amount of methane from earthquakes to better understand sources of the gas.
"We suggest there is a new source that they might want to consider in the future," said David Fischer, postdoctoral researcher at the University of Bremen in Germany and the lead author of the study, according to The New York Times.
The study was based on data from the Makran subduction zone. A strong 8.0 magnitude earthquake that hit Pakistan in 1945 triggered a tsunami, killing about 4,000 people.
The Arabian Plate off the coast of Pakistan is sliding northward by about 1.5 inches per year.
In the current study, experts found that there was a vast amount of methane seeping from the seabed near the Makran subduction zone. Based on the rate of accumulation of methane in the region, they found that the gas has been leaking since 1945.
"Three lines of evidence came together saying the earthquake triggered the amplification of the methane flux," said Fischer, nbc.news.com reported.
There are many reservoirs of methane in oceans around the world. Under certain conditions, the gas forms icy compounds called gas hydrates. Top layers of these hydrates plug the reservoir and prevent the ice from escaping.
For the study, scientists analyzed sediment cores taken in 2007 from two locations in the Arabian Sea. They found that a strong earthquake had released methane in that region. "The quake broke open gas-hydrate sediments and the free gas underneath migrated to the surface," he said, according to The New York Times.
It is known that movement of tectonic plates can release methane, but this is the first time that a single quake caused a massive release of methane; about 10 million cubic yards of gas released over the years. The amount of methane released immediately after the 1945 earthquake could have been higher, they explained.
Note that methane is a more potent greenhouse gas than carbon dioxide and its release could worsen climate change. Experts believe that warmer oceans could lead to icy hydrates dissolving and releasing even more methane. A previous research reported that a massive release of methane in the ocean around 183 million years ago, led to the disappearance of many marine organisms.
The present study is published in the journal Nature Geoscience.
Methane was in news last week too with a commentary published in Nature claiming that release of the gas in the Arctic region was triggering a kind of climate change "time bomb" that could lead to huge economic losses. However, many researchers believe that this methane trigger from Arctic may not impact earth's climate.
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