Mysterious "Swarm" of Quakes Strikes Oregon Water
by Richard A. Lovett
http://news.nationalgeographic.com/news/2008/04/080416-oregon-quakes.html
16 Apr 2008

This weekend scientists will try to puzzle out the cause of a "swarm" of earthquakes that has shaken the seafloor near Oregon in recent weeks.
About 600 earthquakes have been recorded in a small region about 190 nautical miles (350 kilometers) offshore from Yachats.

Although most of the temblors were small, about magnitude 2 or 3, a few were magnitude 4 or 5.

Earthquake swarms normally indicate volcanic activity. But they could represent stresses being released in an unusual manner in the middle section of the Juan de Fuca plate.

The scientists say they may find lava oozing out onto the seafloor or hot water percolating up from magma-heated undersea hot springs. They could also come across colder water squeezed out of the underlying crust by tectonic forces.

All of this, the scientists say, is an example of how much we still have to learn about ocean tectonics.

To begin with, said Robert Embley of NOAA's Pacific Marine Environment Laboratory, the area isn't even well mapped.

"We don't really know what the topography looks like out there," he said. "Our good maps are just along the plate boundary, where 98 percent of the [normal] seismic activity occurs."

And we wonder why our oceans are heating.

"Elsewhere, the ocean floor is basically unmonitored," Embley said.

The Sounds of Climate Change

Underwater volcanoes heating the seas?
8 Jan 2008

http://www.oregonlive.com/news/oregonian/index.ssf?/base/news/1199514313113650.xml&coll=7&thispage=1

Researchers from the Oregon State University (OSU) Hatfield Marine Science Center have journeyed to the Antarctic region over the past 3 years to deploy hydrophones into the deep waters surrounding the western Antarctic Peninsula.

The hydrophones are highly sensitive microphones encased in titanium and lowered on three-quarters of a mile of cable to listen to the rumble of undersea earthquakes.

"When an earthquake occurs, it makes a distinct sound, and we can locate that," says Robert Dziak, 44, OSU associate professor of marine geophysics and expedition leader.

 

"Earthquakes and magma spewing on the seafloor go hand in hand, and what we are seeing is, there are new heat sources right off the coast of Deception Island that no one was aware of before.

"It's the only place on the planet where active seafloor and subaerial (above sea level) volcanoes are near large icebergs and ice sheets."

Dziak hopes to learn more about how the sea floor volcanoes and earthquakes contribute to the breakup of ice in the region. The most significant find from the research so far has been the discovery of thermal vents on the seafloor.

"Since three-quarters of the Earth is covered by ocean, the vast majority of volcanic activity on Earth is occurring without our knowledge undersea."

So it's unknown how much heat and chemicals the underwater volcanoes spew into the ocean and atmosphere (italics added), affecting global ocean temperatures and climate, said Dziak.

According to Haru Matsumoto, research associate at OSU, scientists know that the air temperature around the Western Antarctic Peninsula has warmed by 4 degrees Fahrenheit during the past 40 years and that noise levels in the waters nearby have increased about 10 decibels in the past 30 years.

Matsumoto says the louder noise levels of the past four decades may be the result of global warming.

(How in the world did Matsumoto reach that conclusion? Wouldn’t a more reasonable conclusion be that the increased underwater volcanic activity is causing global warming?)
 

Warming Deep-Sea Temperatures Ended Last Ice Age
Study Validates My Theories

by Terah U. DeJong
http://www.usc.edu/uscnews/stories/14288.html 
27 Sep 2007

USC College researcher shows that deep-sea temperatures rose 1,300 years before the buildup of atmospheric carbon dioxide, ruling out CO² as driver of the last ice age’s meltdown.

In contrast to what is often inferred from the geologic record, carbon dioxide did not cause the end of the last ice age, a new USC study published in Science suggests.

"There has been this continual reference to the correspondence between CO² and climate change as reflected in ice core records as justification for the role of CO² in climate change," said paleoclimatologist Lowell Stott, the study’s lead author and a professor of earth sciences at USC College.

"You can no longer argue that CO² alone caused the end of the ice ages."

Deep-sea temperatures warmed about 1,300 years before the tropical surface ocean and well before the rise in atmospheric CO², the study found. The finding suggests the rise in greenhouse gas was likely a result of warming – but not its main cause.

(Rising CO² levels are a result of warming, not a cause - just as I say in "Not by Fire but by Ice.")

"What this means is that a lot of energy went into the ocean long before the rise in atmospheric CO²," Stott said.

But where did this energy come from? Evidence pointed southward.

The warming deep water appeared to come from the Antarctic Ocean, then moved northward, the scientists wrote

In addition, the researchers noted that the increases in deep-sea temperature coincided with the retreat of Antarctic sea ice, both occurring 19,000 years ago, before the northern hemisphere’s ice retreat began.

Finally, Stott and colleagues found a correlation between melting Antarctic sea ice and increased springtime solar radiation over Antarctica, suggesting this was the energy source.

As the sun pumped in heat, the warming accelerated because of sea-ice albedo feedbacks, in which retreating ice exposes more of the ocean that can absorb heat from the sun, much like a dark T-shirt on a hot day, and this results in more melting.

In addition, the authors’ model showed how changed ocean conditions may have been responsible for the release of CO² from the ocean into the atmosphere, which like the albedo feedbacks, also accelerated the warming.

(I also say this in "Not by Fire but by Ice" – that rising CO² levels come from the warming ocean.)

The link between the sun and ice age cycles is not new. The theory of Milankovitch cycles states that periodic changes in Earth’s orbit cause increased summertime solar radiation in the northern hemisphere, which controls ice size.

If CO² caused the warming, one would expect surface temperatures to increase before deep-sea temperatures, since the heat slowly would spread from top to bottom. Instead, carbon-dating showed that the water used by the bottom-dwelling organisms began warming about 1,300 years before the water used by surface-dwelling ones, suggesting that the warming spread bottom-up instead.

(Just as I say in "Not by Fire but by Ice." It’s not global warming, it’s ocean warming. And this time it’s leading us into an ice age.)

Stott is an expert in paleoclimatology and was a reviewer for the Intergovernmental Panel on Climate Change. He also recently co-authored a paper in Geophysical Research Letters tracing a 900-year history of monsoon variability in India.
 

Unrecognized underwater volcanic activity
http://www.sciencedaily.com/releases/2007/07/070712134521.htm
13 Jul 2007

Many earthquakes in the deep ocean are much smaller in magnitude than expected. Geophysicists from the Woods Hole Oceanographic Institution (WHOI) have found new evidence that the fragmented structure of seafloor faults, along with previously unrecognized volcanic activity (italics added), may be dampening the effects of these quakes.

Examining data from 19 locations in the Atlantic, Pacific, and Indian oceans, researchers led by graduate student Patricia Gregg have found that "transform" faults are not developing or behaving as theories of plate tectonics say they should. Rather than stretching as long, continuous fault lines across the seafloor, the faults are often segmented and show signs of recent or ongoing volcanism.

Both phenomena appear to prevent earthquakes from spreading across the seafloor, thus reducing their magnitude and impact.

Gregg, a doctoral candidate in the MIT/WHOI Joint Program in Oceanography and Oceanographic Engineering, conducted the study with seismologist Jian Lin and geophysicists Mark Behn and Laurent Montesi, all from the WHOI Department of Geology and Geophysics.

Their findings were published in the July 12 issue of the journal Nature.

Oceanic transform faults cut across the mid-ocean ridge system, the 40,000-mile-long mountainous seam in Earth’s crust that marks the edges of the planet’s tectonic plates. Along some plate boundaries, such as the Mid-Atlantic Ridge, new crust is formed. In other regions, such as the western Pacific, old crust is driven back down into the Earth.

If you imagine the mid-ocean ridge as the seams on a baseball, then transform faults are the red stitches, lying mostly perpendicular to the ridge. These faults help accommodate the motion and geometry of Earth’s tectonic plates, cracking at the edges as the different pieces of rocky crust slip past each other.

The researchers [examined] gravity data collected over three decades by ships and satellites, along with bathymetry maps of the seafloor.

Conventional wisdom has held that transform faults should contain rocks that are colder, denser, and heavier than the new crust being formed at the mid-ocean ridge. Such colder and more brittle rocks should have a "positive gravity anomaly."

But Gregg,

"was surprised to find that the faults were not exerting extra gravitational pull. On the contrary, many seemed to have lighter rock within and beneath the faults.

"What we found was the complete opposite of the predictions," said Gregg.

"It is also possible that magma, or molten rock, from inside the earth is rising up beneath the faults. (italics added) Earthquakes stem from the buildup of friction between brittle rock in Earth’s plates and faults. Hot rock is more ductile and malleable, dampening the strains and jolts as the crust rubs together and serving as a sort of geological lubricant.

The findings by Gregg, Lin, and colleagues may also have implications for understanding the theory of plate tectonics, which says that new crust (2,150-degree magma) is only formed at mid-ocean ridges.

By traditional definitions, no crust can be created or destroyed at a transform fault. The new study raises the possibility that new crust (2,150-degree magma) may be forming along these faults and fractures at fast-spreading ridges such as the East Pacific Rise.

(It’s not global warming, it’s ocean warming, caused by underwater volcanic activity, and it’s leading us directly into the next ice age.)

This story was originally entitled "Fragmented Structure Of Seafloor Faults May Dampen Effects Of Earthquakes." I think the discovery of so much unexpected underwater volcanic activity is the real news here.


 

Three million underwater volcanoes

by Catherine Brahic

http://environment.newscientist.com/article/dn12218-thousand-of-new-volcanoes-revealed-beneath-the-waves.html

Journal reference: Geophysical Research Letters (DOI: 10.1029/2007GL029874)
9 Jul 2007

Researchers have counted 201,055 underwater cones, 10 times more than have been found before, and estimate that in total there could be about 3 million submarine volcanoes, 39,000 of which rise more than 1000 meters over the sea bed.

"The distribution of underwater volcanoes tells us something about what is happening in the centre of the Earth," says John Hillier of the University of Cambridge in the UK.

That is because they give information about the flows of hot rock in the mantle beneath.

Since the late 1960s, research vessels have been criss-crossing the oceans using sonar instruments to measure the depth of the ocean floor. They have generated 40 million kilometers of linear profiles showing the topography of the ocean bed between 60E° North –– the latitude of southern Alaska –– and 60E° South –– corresponding to the tip of Patagonia.

But until now, no one had been able to sift through them all. So, Hillier and a colleague designed a computer program that was able to analyze the huge amount of data and identify volcano-like shapes in the sonar lines.

The program found 201,055 volcanoes over 100m tall. Previously, satellite data had identified 14,164 volcanoes over 1500 m high.

Hillier then extrapolated the data to estimate how many volcanoes exist beyond the areas the research vessels sounded out.

(If you've read "Not by Fire but by Ice" then you understand how important this is. When I started writing this book, scientists thought there were 10,000 underwater volcanoes in the entire world. Now they think there are three million! As I've been saying all along, it's not global warming, it's ocean warming -heated by underwater volcanoes- and it's leading us into the next ice age.)
 

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