Methane Bubbles From The Seafloor Hint At Offshore Quakes To Come

Methane Bubbles From The Seafloor Hint At Offshore Quakes To ComeMethane bubbles that squeeze out of sediment and rise from the seafloor off the coast of Washington provide important clues to what will happen during a major offshore earthquake, according to a new study.

The first large-scale analysis of these gas emissions finds more than 1,700 bubble plumes, primarily clustered in a north-south band about 30 miles (50 kilometers) from the coast.

Analysis of the underlying geology suggests why the bubbles emerge there: The gas and fluid rise through faults generated by the motion of geologic plates that produce major offshore earthquakes in the Pacific Northwest.

“We found the first methane vents on the Washington margin in 2009, and we thought we were lucky to find them, but since then, the number has just grown exponentially,” says Paul Johnson, professor of oceanography at the University of Washington and lead author of the study in the Journal of Geophysical Research: Solid Earth.

“These vents are a little ephemeral,” Johnson says. “Sometimes they turn off-and-on with the tides, and they can move around a little bit on the seafloor. But they tend to occur in clusters within a radius of about three football fields. Sometimes you’ll go out there and you’ll see one active vent and you’ll go back to the same location and it’s gone. They’re not reliable, like the geysers at Yellowstone.”

Methane Bubbles From The Seafloor Hint At Offshore Quakes To ComeSonar image of bubbles rising from the seafloor off Washington’s coast. This is from a 2014 survey in deeper water: The base of the column is 1/3 of a mile (515 meters) deep and the top of the plume is at 1/10 of a mile (180 meters) depth. (Credit: Brendan Philip /U. Washington)

Open ocean depths

Researchers analyzed data from multiple research cruises over the past decade that use modern sonar technology to map the seafloor and also create sonar images of gas bubbles within the overlying water. The new results show more than 1,778 methane bubble plumes issuing from the waters off Washington State, grouped into 491 clusters.

“If you were able to walk on the seafloor from Vancouver Island to the Columbia River, you would never be out of sight of a bubble plume,” Johnson says.

Methane Bubbles From The Seafloor Hint At Offshore Quakes To ComeRed stars show locations of methane bubble plumes off Washington’s coast. The light gray is the shallow continental shelf, less than 160 meters (175 yards) deep. The blue is the deeper margin and abyssal plain, deeper than 2.8 kilometers. (Credit: Paul Johnson/U. Washington)

The sediments off the Washington coast form as the Juan de Fuca oceanic plate plunges under the North American continental plate, scraping material off the ocean crust. These sediments then heat, deform, and compress against the rigid North American plate. The compression forces out both fluid and methane gas, which emerges as bubble streams from the seafloor.

The bubble columns are located most frequently at the boundary between the flat continental shelf and the steeply sloped section where the seafloor drops to the abyssal depths of the open ocean. This abrupt change in slope is also a tectonic boundary between the oceanic and continental plates.

“Although there are some methane plumes from all depths on the margin, the vast majority of the newly observed methane plume sites are located at the seaward side of the continental shelf, at about 160 meters water depth,” Johnson says.

Methane Bubbles From The Seafloor Hint At Offshore Quakes To ComeThe Washington coast is geologically complex. The bubbles emerge from a region off the coast above where the Juan de Fuca ocean plate plunges beneath the North American continental plate. (Credit: Paul Johnson/U. Washington)

Good for fish

A previous study suggested that warming seawater might be releasing frozen methane in this region, but further analysis showed the methane bubbles off the Pacific Northwest coast arise from sites that have been present for hundreds of years, and not because of global warming, Johnson says.

Instead, these gas emissions are a long-lived natural feature, and their prevalence contributes to the continental shelf area being such productive fishing grounds. Methane from beneath the seafloor provides food for bacteria which then produce large quantities of bacterial film. This biological material then feeds an entire ecological chain of life that enhances fish populations in those waters.

“If you look online at where the satellite transponders show where the fishing fleet is, you can see clusters of fishing boats around these methane plume hotspots,” Johnson says.

To understand why the methane bubbles occur here, researchers used archive geologic surveys that oil and gas companies conducted in the 1970s and 1980s. The surveys, now publicly accessible, show fault zones in the sediment where the gas and fluid migrate upward until emerging from the seafloor.

“Seismic surveys over the areas with methane emission indicate that the continental shelf edge gets thrust westward during a large megathrust, or magnitude-9, earthquake,” Johnson says. “Faults at this tectonic boundary provide the permeable pathways for methane gas and warm fluid to escape from deep within the sediments.”

The location of these faults could potentially provide new understanding of the earthquake hazard from the Cascadia Subduction Zone, which last ruptured more than 300 years ago.

If the seafloor movement during a subduction-zone earthquake occurs closer to shore, and a major component of this motion occurs within the shallower water, it would generate a smaller tsunami than if the seafloor motion were entirely in deep water.

“If our hypothesis turns out to be true, then that has major implications for how this subduction zone works,” Johnson says.

Additional coauthors are from the University of Washington and Oregon State University. The National Science Foundation funded the work.

Source: University of Washington

Related Books

Climate Change: What Everyone Needs to Know

by Joseph Romm
0190866101The essential primer on what will be the defining issue of our time, Climate Change: What Everyone Needs to Know® is a clear-eyed overview of the science, conflicts, and implications of our warming planet. From Joseph Romm, Chief Science Advisor for National Geographic's Years of Living Dangerously series and one of Rolling Stone's "100 people who are changing America," Climate Change offers user-friendly, scientifically rigorous answers to the most difficult (and commonly politicized) questions surrounding what climatologist Lonnie Thompson has deemed "a clear and present danger to civilization.". Available On Amazon

Climate Change: The Science of Global Warming and Our Energy Future second edition Edition

by Jason Smerdon
0231172834This second edition of Climate Change is an accessible and comprehensive guide to the science behind global warming. Exquisitely illustrated, the text is geared toward students at a variety of levels. Edmond A. Mathez and Jason E. Smerdon provide a broad, informative introduction to the science that underlies our understanding of the climate system and the effects of human activity on the warming of our planet.Mathez and Smerdon describe the roles that the atmosphere and ocean play in our climate, introduce the concept of radiation balance, and explain climate changes that occurred in the past. They also detail the human activities that influence the climate, such as greenhouse gas and aerosol emissions and deforestation, as well as the effects of natural phenomena.  Available On Amazon

The Science of Climate Change: A Hands-On Course

by Blair Lee, Alina Bachmann
194747300XThe Science of Climate Change: A Hands-On Course uses text and eighteen hands-on activities to explain and teach the science of global warming and climate change, how humans are responsible, and what can be done to slow or stop the rate of global warming and climate change. This book is a complete, comprehensive guide to an essential environmental topic. Subjects covered in this book include: how molecules transfer energy from the sun to warm the atmosphere, greenhouse gases, the greenhouse effect, global warming, the Industrial Revolution, the combustion reaction, feedback loops, the relationship between weather and climate, climate change, carbon sinks, extinction, carbon footprint, recycling, and alternative energy. Available On Amazon

From The Publisher:
Purchases on Amazon go to defray the cost of bringing you InnerSelf.comelf.com, MightyNatural.com, and ClimateImpactNews.com at no cost and without advertisers that track your browsing habits. Even if you click on a link but don't buy these selected products, anything else you buy in that same visit on Amazon pays us a small commission. There is no additional cost to you, so please contribute to the effort. You can also use this link to use to Amazon at any time so you can help support our efforts.

 

enafarzh-CNzh-TWnltlfrdehiiditjakomsfaptruesswsvthtrurvi

EVIDENCE

What Happens When The Permafrost Thaws?
by Official W5
Almost half of Canada sits on permanently frozen land called permafrost, but climate change is causing it to thaw and…
Annual Assessment of North Cascades Glaciers Finds Shocking Loss of Volume
Annual Assessment of North Cascades Glaciers Finds Shocking Loss of Volume
by Mauri Pelto
The summer of 2019 found the North Cascade Glacier Climate Project in the field for the 36th consecutive summer…
For The First Time, We Can Measure The Human Footprint On Antarctica
For The First Time, We Can Measure The Human Footprint On Antarctica
by Shaun Brooks and Julia Jabour
Most people picture Antarctica as a frozen continent of wilderness, but people have been living – and building – there…
The Air Above Antarctica Is Suddenly Getting Warmer
The Air Above Antarctica Is Suddenly Getting Warmer
by Harry Hendon, et al
Record warm temperatures above Antarctica over the coming weeks are likely to bring above-average spring temperatures…
How Close Is 1.5°C? Depends When You Measure From
How Close Is 1.5°C? Depends When You Measure From
Most scientists studying global warming compare today’s temperatures to those of the late 19th century because that is…
Why Methane Emissions Matter To Climate Change
Why Methane Emissions Matter To Climate Change
by Anthony J. Marchese and Dan Zimmerle
The EPA on Aug. 29 unveiled a proposal to rescind regulations to limit methane emissions from the oil and gas industry.
French wines show hot dry years are now normal
French Wines Show Hot Dry Years Are Now Normal
by Tim Radford
Records have begun to topple for the world’s finest tipple. French wines can now count 664 years of vintage information…
The Amazon Fire Crisis Has Been 500 Years In The Making – As Brazil's Indigenous People Know Only Too Well
The Amazon Fire Crisis Has Been 500 Years In The Making – As Brazil's Indigenous People Know Only Too Well
by Darren Reid
São Paulo – the largest city in the Americas – was recently plunged into darkness in the middle of the day due to smoke…

LATEST VIDEOS

Bill Nye And The Climate Crisis
by MSNBC
On a special show before a live studio audience, Bill Nye the science guy discusses the climate crisis with Chris Hayes.
How Greenland's Massive Ice Melt Will Totally Transform The World
by Channel 4 News
Remember that heatwave back in August? Well, the Arctic remembers it too. Record rates of ice melt have been recorded…
China Is Positioned To Lead On Climate Change As The US Rolls Back Its Policies
China Is Positioned To Lead On Climate Change As The US Rolls Back Its Policies
by Kelly Sims Gallagher and Fang Zhang
As the effects of climate change become more widespread and alarming, U.N. Secretary-General António Guterres has…
What Happens When The Permafrost Thaws?
by Official W5
Almost half of Canada sits on permanently frozen land called permafrost, but climate change is causing it to thaw and…
We Are Striking to Disrupt the System: An Hour with 16-Year-Old Climate Activist Greta Thunberg
by Democracy Now!
In her first extended broadcast interview in the United States, we spend the hour with Greta Thunberg, the 16-year-old…
Annual Assessment of North Cascades Glaciers Finds Shocking Loss of Volume
Annual Assessment of North Cascades Glaciers Finds Shocking Loss of Volume
by Mauri Pelto
The summer of 2019 found the North Cascade Glacier Climate Project in the field for the 36th consecutive summer…
Breakdown In Coral Reef Iconic Spawning Puts Species At Risk Of Extinction
Breakdown In Coral Reef Iconic Spawning Puts Species At Risk Of Extinction
by Heidi Burdett
Breakdown In Coral Reef Iconic Spawning Puts Species At Risk Of Extinction
How Climate Change Is Driving Emigration From Central America
How Climate Change Is Driving Emigration From Central America
by Miranda Cady Hallett
Clouds of dust rose behind the wheels of the pickup truck as we hurtled over the back road in Palo Verde, El Salvador.

LATEST ARTICLES

How Climate Change Could Threaten The World’s Traditional Food Dishes
How Climate Change Could Threaten The World’s Traditional Food Dishes
by Daisy Dunne
Climate change is likely to alter the way that the world grows, trades and enjoys food.
Bill Nye And The Climate Crisis
by MSNBC
On a special show before a live studio audience, Bill Nye the science guy discusses the climate crisis with Chris Hayes.
How Greenland's Massive Ice Melt Will Totally Transform The World
by Channel 4 News
Remember that heatwave back in August? Well, the Arctic remembers it too. Record rates of ice melt have been recorded…
China Is Positioned To Lead On Climate Change As The US Rolls Back Its Policies
China Is Positioned To Lead On Climate Change As The US Rolls Back Its Policies
by Kelly Sims Gallagher and Fang Zhang
As the effects of climate change become more widespread and alarming, U.N. Secretary-General António Guterres has…
We Need More Carbon In Our Soil To Help Australian Farmers Through The Drought
We Need More Carbon In Our Soil To Help Australian Farmers Through The Drought
by Nanthi Bolan
Australia has never been a stranger to droughts, but climate change is now super-charging them.
Climate Breakdown Is Pushing Brazil's Iconic Araucaria Tree To Extinction
Climate Breakdown Is Pushing Brazil's Iconic Araucaria Tree To Extinction
by Oliver Wilson
For hundreds of thousands of years, the distinctive candelabra shapes of Araucaria trees (Araucaria angustifolia) have…
Roiled By Trump Politics, NOAA Seeks Accountability, Atonement
by MSNBC
Rachel Maddow reports on the backlash within the weather science community over an unsigned statement from NOAA…
Extreme Cities: Ground Zero for Climate Change
by The Laura Flanders Show
No matter how we tackle climate change, cities are key.