Okmok Volcano

Okmok Volcano

Okmok Volcano on Unmak Island, Alaska continues to produce explosions and ash plumes through a newly created vent and poses hazards to air travel in the area. Scientists are using a combination of seismic and GPS instruments on the ground and weather and radar satellites in space to track the progress of the eruption. Human visual observations are limited because airborne ash obscures a view of what is happening inside the volcano's 6-mile-diameter caldera and the area is too hazardous to enter. "We are dealing with a scientific challenge because the volcano went from very quiet to a large eruption, putting ash to high altitudes with almost no warning," said John Power, Acting Scientist in Charge of the Alaska Volcano Observatory (AVO). The powerful eruption in the Eastern Aleutian Islands began unexpectedly on July 12, sending up a wet, ash and gas-rich plume that reached an altitude of 50,000 ft above sea level. Heavy ash fall occurred on eastern Umnak Island. A dusting of ash fell in the busy fishing community of Unalaska, 65 miles northeast of Okmok volcano. The ash plume soon spanned several hundred miles across the North Pacific, causing many trans-Pacific flights to be diverted and cancellation of flights to the Dutch Harbor airport. The gas cloud from the eruption is now over Montana. The eruption also destroyed or damaged seismic and deformation sensing equipment at two monitoring stations. A third station has lost its communication pathway due to destruction at the other two. Seismic equipment relays earthquake information and GPS equipment is used in monitoring the deformation of the ground surface in response to magma movement. Seven seismic stations are still operational and seismicity has gradually decreased in intensity since the initial eruption. At a minimum, activity at Okmok is likely to continue for days or weeks. Strong gas-driven explosions can produce rock ballistics or larger volcanic debris that can be hurled beyond the crater rim of the volcanic caldera, potentially landing in surrounding areas several miles away. Fast moving clouds of ash, larger debris, and hot gas can form and flow across the caldera floor, rise up over the caldera wall and continue to flow down Okmok's flanks. Rain mixed with ash could create mudflows and rapid flooding along island drainages. As soon as conditions allow, AVO scientists will travel to the volcano in order to document and understand the sudden onset of explosive activity and repair damage to monitoring equipment. The Okmok caldera formed during catastrophic eruptions 12,000 and 2,000 years ago. There are about a dozen cones within the modern caldera that formed in the last 2000 years, and the most recent eruptive activity occurred in 1945, 1958 and 1997. One violent eruption of Okmok in 1817 produced many feet of ash and "scoria" rock debris on the northeastern caldera rim, as well as ash fall on Unalaska Island and floods that buried an Aleut village at Cape Tanak on the northeast Bering Sea Coast of Umnak Island. USGS is responsible for issuing timely warnings of potential volcanic disasters to affected communities and civil authorities.

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Plowing the Ancient Seas: Iceberg scours found off South Carolina

Plowing the Ancient Seas: Iceberg scours found off South Carolina

FLOW REVERSAL. Currents driving the icebergs that scoured channels in the seafloor off South Carolina at the height of the last ice age ran almost exactly opposite to today's prevailing currents. Channel shown in inset is about 100 meters wide.Hill, et al. Recent sonar surveys off the southeastern coast of the United States have detected dozens of broad furrows on the seafloor—trenches that were carved by icebergs during the last ice age, researchers suggest. The channels, roughly parallel to the coast, are between 10 and 100 meters wide and typically less than 10 m deep, says Jenna C. Hill, an oceanographer at Coastal Carolina University in Conway, S.C. She and her team discovered the enigmatic features while conducting oceanographic surveys about 100 kilometers off Georgetown, S.C., in the summer of 2006. Waters in the area range between 170 and 220 m deep, she notes. Most of the trenches run along straight paths for several kilometers, and one lengthy furrow stretches almost 20 km. Short berms alongside each groove are presumably composed of material that was plowed aside when the channels were carved, says Hill. The seafloor features generally run in a southwest-northeast direction. However, the researchers noticed that some of the channels they discovered during a second survey last summer ended with a semicircular pit at their southwestern terminus. Suddenly, says Hill, the features made sense: Icebergs had plowed the furrows, and pits marked the sites where the ice masses became grounded and later melted. The seafloor culs-de-sac indicate that the currents driving the icebergs flowed to the southwest, opposite to prevailing currents today. At present, warm waters of the northeast-flowing Gulf Stream bathe the region, says Hill. However, she and her colleagues suggest that an offshore shift in the Gulf Stream at the height of the last ice age—when sea levels were more than 100 m lower than they are now—would have allowed glacially fed, iceberg-rich coastal currents to penetrate this far south. Hill and her colleagues presented their findings last month in San Francisco at a meeting of the American Geophysical Union. The team's theory "makes dynamical sense," says John M. Bane, Jr., an oceanographer at the University of North Carolina at Chapel Hill. Even today, he says, a seafloor feature about 100 km southwest of the berg-scoured region—a broad area called the Charleston Bump—can cause instabilities in the Gulf Stream that deflect the current offshore for a few weeks at a time, causing reversals in the coastal current. At the height of the last ice age, when sea levels were substantially lower, the Gulf Stream may have been more frequently, if not permanently, deflected offshore.

THE LOST OCEAN

THE LAST OCEAN

LOSERS AND WINNERS. More acidic waters could be tough on the tiny coccolithophore Emiliania huxleyi (left), which builds a shell of calcium-carbonate platelets; but comfy for nitrogen-fixing cyanobacteria such as Trichodesmium (right).Björn Rost; David Caron/Univ. of Southern California Adding heat Increased CO2 also means the corals will have to contend with temperature increases. Depending on the coral species and the place, 3 to 4 weeks of temperatures a degree or two Celsius above current summer peaks can turn a reef into a spooky white sculpture of itself. This bleaching comes from the breakdown of the partnership between warm-water, soft-bodied corals and their colorful live-in algae, or zooxanthellae. They photosynthesize, and the host corals take a share of the lunch. Sometimes the partners get together again after a bleaching break-up, but prolonged absence of zooxanthellae kills a shallow-water coral. Studies of zooxanthellae during the past decade have revealed unsuspected variety in the alga's capacity to endure heat. Corals primarily colonized with a variant called the D strain withstand heat better than others, according to Ray Berkelmans of the Australian Institute of Marine Science in Townsville. Researchers including Andrew Baker of the University of Miami in Florida are working to develop reef-saving therapies that swap out fragile zooxanthellae strains for heat-savvy ones. The strategy doesn't brighten Hoegh-Guldberg's view of coral futures if carbon emissions keep soaring. Heat waves have bleached corals widely in recent years, but Hoegh-Guldberg hasn't seen the zooxanthellae adapting naturally. "Everyone's had enough time to show magical adaptation of corals," he says. Another hope for adaptation swirls through conversations about coral reefs, but it doesn't cheer Hoegh-Guldberg either. Atmospheric carbon dioxide has spiked and ocean pH has plunged before in Earth's history. So the question arises of whether corals could just do whatever it was they did to survive last time. "That's crap," says Hoegh-Guldberg. Ancient corals would have had more time than today's to get up to speed on hot, lower-pH life, he says. Again he flips open the Science paper and jabs a finger at some data. He and his colleagues used published measurements from air bubbles trapped in ancient ice to calculate rates of change for CO2 concentrations in the atmosphere. The concentrations have risen more than 1,000 times faster per century during the industrial revolution than during the previous 420,000 years, the team concludes. Also, Hoegh-Guldberg says he's not convinced that calcifying organisms did manage to laugh off earlier planetary burps of greenhouse gases. During the early Triassic, for example, CO2 concentrations reached levels five times as high as today's. He notes a gap in the fossil record during this time of evidence for both the reef-building corals and the algae that sculpt carbonate. Some lineages of today's corals are ancient enough to have survived hot spells with funky ocean chemistry. Yet those lineages that survived may have done so without calcified skeletons. "They essentially became anemones," he says. That's survival for lineages that can do it, but it's still not a happy ending to Hoegh-Guldberg. Even if all today's corals successfully turned into naked, soft-bodied bits—more magic adaptation perhaps—other reef species would still end up homeless. The intricate crags and crevices of reefs shelter much of the biodiversity of oceans, perhaps a million species. Without complex reef habitats built by corals, it will be a simpler ocean, he says. Floating hubcaps Beings smaller than corals, some of the mere specks of life that drift in the seas as plankton also need calcium carbonate to build. Microscopic coccolithophores, up until now not exactly famous, have become iconic in the study of ocean pH change, thanks to Ulf Riebesell of the Leibniz Institute of Marine Sciences in Kiel, Germany. The celebrity plankton look like a craft project of hubcaps welded around a giant beach ball. The ornate hubcaps, platelets made of calcium carbonate, enclose a photosynthetic cell. Springtime blooms of coccolithophores such as Emiliania huxleyi can spread over an area the size of Ireland. Light glinting off all the platelets makes milky blue streaks in the sea visible from space. E. huxleyi doesn't follow the corals' recipe for calcifying structures. Yet the coccolithophores also fail to grow normally in low-pH seawater, says Riebesell. In experiments simulating such water, he's seen runt cells with flimsy or even deformed platelets. Growth anomalies are showing up in other marine builder species, such as oysters. And in one of the few studies focusing on larvae, Gretchen Hofmann of the University of California, Santa Barbara, reports difficulties for very young sea urchins. Normal larvae look like alphabet soup "A's." In seawater dosed with extra CO2, though, the larvae grow "shorter and stubbier," she says. Outside the shell Much of the first wave of research on the next ocean has focused on the future of calcification. Not that that's silly. Creatures accounting for 46 percent of the annual U.S. seafood catch form some kind of calcified structure, such as clam shells, says Scott Doney of the Woods Hole Oceanographic Institution in Massachusetts. Adding in species that eat the calcifiers, such as pink salmon fattening up at sea on swimming snails called pteropods, would boost the percentage. Still, water chemistry could affect uncalcified aspects of life for marine species, and research is now branching out into these matters. For example, moving around seems to get more difficult for squid in lower-pH water, according to ongoing research by Brad Seibel of the University of Rhode Island in Kingston, and others. The dip in seawater pH disturbs the oxygen transport in squid blood, and squids get sluggish. That odd future ocean means good news for some species, particularly among the noncalcifiers, says David Hutchins of the University of Southern California in Los Angeles. Nitrogen-fixing cyanobacteria grow better in experiments that mimic ocean acidification. "They really love the CO2," he says. The cyanobacteria's cells, such as those in a Trichodesmium species, don't transport CO2 efficiently from the outside world to their internal energy trapping machinery. A richer mix of the gas outside makes the cells more productive. Who flourishes and who fades among the plankton in the new ocean matters to bigger creatures. The marine grazers that feed on plankton prefer some kinds and shun others. If the plankton equivalent of broccoli gives way to a brussels sprouts equivalent, grazer populations change too. Preferences work their way up to top predators, including those on dry land about to pick up a fork. Considering lab and field experiments simulating future oceans, Hutchins speculates that plankton shifts will mean more microbial predators and less fish in the future oceans. "It's not necessarily going to be a world we particularly like," he says. Whether kelps will like it remains to be seen. Kelp biologist Klinger emphasizes that she's just getting started in answering this question. She puts in a plug for the importance of understanding what will happen to kelp. Much like reefs, clusters of fronds offer complex habitats, with hidey-holes for fish and highways for snails. Also one could argue that a future ocean would be a little less interesting without kelp sex.