Mystery earthquake south of Hawai'i

A mysterious earthquake shook the seafloor between Hawai'i and the Marquesas Islands this morning, in a spot that's not known for temblors.
(Image: Image provided by Google Earth and USGS, annotated by the author.)

It wasn't a huge event, just a 5.4, but it was enough to set up a chatter between the folks at the U.S. Geological Survey who watch these things. They said there is no reason to believe it could presage another, bigger event.

The quake happened at 5:40 a.m. Hawai'i time on Friday, February 29, a little more than an hour before this posting.

The site was below the surface of the ocean floor, at 3.08 degrees north and 140.34 degrees west longitude. That's just northwest of the Marquesas and southeast of Hawai'i, a little north of the Equator.

It is an odd and unusual place for a quake, although such events are not unheard-of, said Barry Hirshorn, a geophysicist with the Pacific Tsunami Warning Center.

Most of the earthquakes around the Pacific occur at the edges of the vast Pacific Plate, one of the chunks of the earth's crust that are constantly in movement, shoving up against each other, rising up or slipping under each other, or sliding alongside each other. The perimeter of the Pacific Plate is familiarly known as the Ring of Fire, because of all the volcanic activity that is associated with the plate fringe.

There are also frequent quakes around Hawai'i, associated with both the activity of the volcanoes and the weight of the islands on the center of the plate.

But at the site of this morning's event, there are no islands, no volcanoes, no fault lines, and it's nowhere near the edge of the Pacific Plate. Hirshorn said he had discussed the event with folks at the Alaska warning center, who had also seen it on their instruments.

“You can have false readings, but this is a real quake. It's the middle of the plate. It's pretty rare to have that happen, but you can have residual areas of stress that build up” and cause an event, he said.

The quake was comparatively shallow, about 4 miles deep.

For information on the quake, see earthquake.usgs.gov/eqcenter/recenteqsww/Quakes/us2008pabx.php.

© 2007 Jan W. TenBruggencate

Airborne dust over Hawai'i impacts climate change

That dust that appears magically on your windowsill in Hawai'i?

It may be better-traveled than you are.

(Image: Here, airborne dust from the Sahara is seen as a brown haze over the Caribbean. The same thing happens in the Pacific, with dust from both Asia and South America. NOAA photo from the GOES8 satellite.)

There's a fair chance some of the material on the windowsill is Asia dust, lately resident of Chinese deserts or the smokestacks of China industry.

“Each year, long-distance winds drop up to 900 million tons of dust from the deserts and other parts of the land into the oceans,” write a team of researchers who have studied the issue.

Earlier work suggests Asian dust storms may have dumped enough material on the Islands to increase the fertility of worn-out volcanic soils. The most recent studies, looking at ocean sediments, suggest that dust volume is associated with climate change.

Researchers led by geochemist Gisela Winckler, of Columbia University's Lamont-Doherty Earth Observatory, studied seafloor sediments across 6000 miles of the Pacific south of Hawai'i—along the Equator from New Guinea to the Galapagos.

“Dust from Asia travels long ways, including Hawai'i and the West coast of the U.S., for example. In our study we present geochemical evidence that the dust in the central and western tropical Pacific (at the equator) is of Asian origin while the dust in the eastern equatorial Pacific is predominantly

derived from South America,” Winckler said in an email to RaisingIslands.

The paper, with the unfortunate title “Covariant glacial-interglacial dust fluxes in the equatorial Pacific and Antarctica,” was written by Winckler, Martin Fleisher, Robert Anderson and David McGee, all of Columbia, and Natalie Mahowald of Cornell. It was to be published today (Feb. 28) at the ScienceExpress website.

The dust is high in a range of nutrients—more on that later.

They used the isotope thorium 232 to track land dust—if you find this isotope in the remote ocean, it's generally from land-sourced dust. And they used various other isotopes to identify where the dust came from. Most on the western side of the Pacific came from Asia. On the Galapagos side, it tended to come from South America.

They also compared their data with information from previous cores done in Antarctica, where the main source of dust is Patagonia. Both sets of cores showed that during ice ages, there's a spike in the amount of continental dust deposited in the oceans.

Why do we care about dust? Because, as the paper says, “dust affects climate.” It may even be acting as a kind of feedback mechanism.

With more dust in the air, sunlight (and heat) is radiated back into space—helping keep the Earth's temperatures cool.

Dust has considerable amounts of iron, and it may fertilize the oceans, causing them to grow more plants and to suck carbon-dioxide out of the atmosphere. The reduced carbon-dioxide would lessen the atmosphere's ability to hold heat, and would further support cooling.

Other researchers have considered dumping iron into the oceans as a way of fertilizing them, causing themto take up more carbon-dioxide, all in hope that the stuff would sink to the deep sea and be hidden away for a long time. Winckler and her team, in a press release, say the jury is still out on how well that would work.

“A dozen early experiments in different regions have shown that plankton growth increases when iron is artificially added, but scientists have yet to show that this could lock significant amounts of CO2 into the ocean...The new data gives us a natural experiment to see what might have happened in the past.

They plan to study their sediment cores to see if they also include high levels of carbon, which might indicate carbon was effectively being sequestered.

The scientists say it's not entirely clear why there's more dust during ice ages, but it seems clear that there is a relationship between more cold and more dust.

Or, to let them use their own words:

“Although there is uncertainty concerning the complex interplay of the factors influencing dust generation in any particular region, we infer from the synchronous changes in dust fluxes seen in our records that in each of the source areas, i.e. Asia, northern South America and Patagonia, the dominant processes regulating dust generation experienced a coherent response to global climate change.”

© 2007 Jan W. TenBruggencate

Oh, the slime! Slugs a threat to native ecosystems

Gardeners have long known the threat of garden slugs to their seedlings, but natural resources managers are only now recognizing that the slimy critters are also significant threats to rare native plants.

(Images of slugs in the Hawaiian environment courtesy Stephanie Joe. The spotted character at the top is a large European native named Limax maximus. She's a pet, and Joe calls her Destiny.)

“Slug herbivory may be skewing species abundance in favor of certain non-native and native plants,” wrote University of Hawai'i botanist Stephanie Joe and UH botany professor Curtis Daehler, in an article in the journal Biological Invasions.

Their article is entitled “Invasive slugs as under-appreciated obstacles to rare plant restoration: evidence from the Hawaiian Islands.”

Garden stores sell slug bait, which home gardeners use to keep slugs from munching their new seedlings right down to the ground. But this is not something the first residents of the Islands had to face.

There were no native slugs in Hawai'i before humans arrived. The slugs' relatives, tree snails like the famed and generally endangered Achatinella, were animals that did not appear to eat plants. They crawl on leaves of forest plants but don't eat the leaves themselves. Rather, they feed on the algae and fungi that grow on plants.

But a dozen or more species of slugs have appeared in the Islands over time. They are not well studied, Daehler said, and it's not really clear how many species there are, or exactly where they are.

However, “they are pretty widely distributed. Everywhere we've looked, we find evidence of them,” he said.

There are warm-weather slugs in the lowlands, and slugs from temperate regions in the cooler high forests.

To determine what their impact on native plants might be, Joe and Daehler developed experiments that involved growing seedings of two endangered native plants, Cyanea superba and Schiedea obovata, a non-endangered native, Nestegis sandwicensis (Olopua), and two weeds, Psidium cattleianum (strawberry guava) and Clidemia hirta (Coster's curse).

They planted the seedings out in the forest in the Waianae mountains, and watched what happened.

It wasn't pretty.

“In our field study, both of the critically endangered species had 50 percent higher mortality when exposed to slugs,” they wrote. The greehouse-grown plants were comparatively large when they were planted in the forest, and the authors feel the loss could be higher for tiny naturally germinating seedings.

The slugs did not appear to similarly damage the weedy alien species, or even the non-endangered Olopua, which may give these plants a competitive advantage at the same time the rarest Hawaiian natives are being knocked down by slugs.

And it's not just seedings that are affected.

“We've seen that they climb up on larger plants and burrow into the plant. A lot of them can climb up defoliate a bush-sized plant,” Daehler said.

The research has serious implications for the protection of native plant communities. For a time, it seemed enough to fence out deer, goats and pigs. Then scientists found that rats were a major problem, and they used both traps and poisons to control them. Now it appears slugs will also need to be controlled.

“Slug and snail control measures have generally not been used in the management of rare plants in Hawaii, nor have published studies documented their use to facilitate rare plant restoration on other islands around the world, where endemic plants might be expected to be highly susceptible to introduced herbivores,” The Joe-Daehler paper says.

“The implications are especially relevant for rare plant outplantings and population restoration efforts... Outplanted seedings that are unprotected from slug predation may suffer from high mortality.”

Hawai'i's native tree snails are not known to be herbivores. They crawl on leaves but don't eat the leaves themselves. Rather, they feed on the algae and fungi that grow on plants.

© 2007 Jan W. TenBruggencate

New Kauai shoreline erosion bill among nation's most conservative

Kaua'i County has adopted the most aggressive shoreline building setback law in the state, a powerful policy that aims to protect coastal structures against 70 to 100 years of erosion.

(Image: Kaua'i map with red boxes showing areas where erosion studies have been completed. This interactive image is available online at www.soest.hawaii.edu/asp/coasts/kauai/index.asp. Courtesy Chip Fletcher.)

Coastal geologist Chip Fletcher, of the University of Hawai'i's School of Ocean and Earth Science and Technology, said the Kaua'i legislation may represent the most conservative coastal erosion position in the nation.

The new law, passed by the County Council and signed by the mayor, declares its provisions to be both a public safety and a planning measure.

Pushing buildings back from eroding waterlines, the law says, “is critical to the protection of life and property, the mitigation of coastal hazards, and the preservation of coastal resources.”

The issue, in part, is that if government allows people to build within a few dozen feet of the shore, and erosion threatens to undermine foundations, then there are powerful financial incentives to protect the structures—and you end up with rock walls instead of sandy beaches. Coastlines where people can't pitch their beach umbrellas, where anglers can't set up poles and beach chairs and coolers, where monk seals and turtles can't haul out, and where the classic look of a tropical beach is destroyed.

Under the new legislation, there are two potential ways of calculating how close to the water a structure can be erected.

On shallow lots whose depth from the certified shoreline to the back of the lot averages 100 feet or less, a building could be built as near as 40 feet. On deeper lots, the setback grows. If the lot depth is 130 feet, the setback is 60 feet. If it's 180 feet, the setback is 80 feet.

On larger lots, a coastal erosion study would be required, and it would establish the rate at which the shoreline is eroding.

For structures of less than 5,000 square feet, the setback would be 40 feet plus 70 times the annual erosion rate. The goal is that 70 years from now, if the erosion continues, the building would presumably be near the end of its useful life, and would still be 40 feet from the water.

For bigger buildings, with square footages greater than 5,000, the setback would be 40 feet plus 100 times the erosion rate.

So, on a coastline that's eroding at a foot a year, a normal-sized house would require a 110-foot setback, and a big hotel would require a 140-foot setback.

The Kaua'i bill is considerably stronger than the state's first such legislation, Maui's bill. The Maui setbacks are 25 feet plus 50 times the erosion rate.

For comparison, on a beach with one foot of erosion per year, a Maui home would be set back 75 feet from the certified shoreline (25 feet plus 50), while the same house on Kaua'i would be set 110 feet back (40 feet plus 70).

To learn more about coasts, see the University of Hawai'i Coastal Geology website at http://www.soest.hawaii.edu/coasts.

Erosion maps, showing coastlines where the erosion rates have been determined, are available:

For O'ahu: www.soest.hawaii.edu/asp/coasts/oahu/index.asp.

For Maui: www.soest.hawaii.edu/asp/coasts/maui/index.asp.

For Kaua'i: www.soest.hawaii.edu/asp/coasts/kauai/index.asp.

One of the interesting features of the maps is that they indicate that on many shorelines, land is actually building up. Accretion and erosion both are features of Hawaiian shorelines, and some shores have some of both, depending on where along the coast you look.

As a result of this, on many coastlines, the dramatic Kaua'i setback legislation would not take effect. If there's no documented erosion, then the issue doesn't come into play.

© 2007 Jan W. TenBruggencate

"Earth: The Sequel," a positive view of the environmental future

“Earth: The Sequel,” a new book coming out in March 2008 from Environmental Defense Fund, provides one of the most hopeful views yet of the possible future of the planet.

And while Hawai'i isn't specifically in the book, most of the technologies it reviews have Hawaiian analogues.

Its subtitle is “The race to reinvent energy and stop global warning,” and unlike virtually every other environmental book you will read, it is unfailingly positive in its outlook.

The message: human ingenuity and technology can save us, if only we let them.

“Earth: The Sequel,” written by Environmental Defense Fund president Fred Krupp and Miriam Horn, is at its core is a compilation of the some of the most forward-looking energy initiatives that are either under design or being built.

Scientists modifying microorganisms to make fuels that can be used in existing cars—does this sound like the recently announced program to make biofuels out of algae on the Big Island? .

Wave energy technologies—nothing new to Hawaii, which has one in place already off O'ahu and a different one scheduled to be installed off Maui.

There's the Alaskan inventor using subterranean heat to keep his ice hotel frozen in summer—a technology that won't be new to those familiar with the geothermal plant on the Big Island.

But the book goes beyond technologies familiar to the Islands as well, to new battery systems, improved and cheaper photovoltaics, kite wind systems, carbon sequestration research and much more.

The book's message is that the great inventors and their great ideas are out there. All they need is a fair playing field. As long as tax subsidies and government policies favor petroleum and coal, inventiveness will be inhibited and climate change will roll over us.

It is, authors Krupp and Horn say, a “near certainty that unless the United States acts as a nation to give these innovators the chance to compete fairly in the worlds biggest business, they will fail to avert the crisis in time.”

Their proposal is to recognize the cost of carbon emissions.

“Policymakers are only just beginning to confront the huge hidden subsidy for fossil fuels: that no financial account is taken of the use of the atmosphere as a dumping ground for the pollutants that cause global warming,” they write.

Read more about the book at earththesequel.environmentaldefense.org.

© 2007 Jan W. TenBruggencate