Chile's Raised Coast
Caleta Yane
The Chilean earthquake that struck on Feb. 27 changed the country's landscape by raising the ground near the coast and sinking land farther inward, a new study finds. Here on the Arauco Peninsula, the uplift of a marine terrace displaced the coastline about 980 feet (300 meters) seaward
New coast
Uplift of the ground is seen at the beach of Lebu. Uplift in this zone was about 71 inches (180 centimeters), which produced the uplift of a great marine platform.
Punta Lavapié
An uplifted marine platform was found at Punta Lavapié (the northernmost tip of the Arauco Peninsula). Here, the coastline before the earthquake was just at the foot of the cliff.
This photograph shows several species of dead algae and mollusks that lived in the coastal waters.
The white coating on the rocks is from the dead algae. Researchers used the white fringe to measure how far the land had risen after the earthquake. These normally pink algae, common in Chilean coastal waters, are bleached and dried out by sunshine. The algae died and turned white when the land was pushed above the water's surface.
Santa Maria Island
At the southern end of Santa Maria Island, several marine platforms uplifted more than 5 feet (1.5 m), leaving some species far from their living zone. Sea lions, seen here, are now more than 16 feet (5 m) from sea-level.
Arauco Peninsula
The magnitude 8.8 earthquake also caused massive landslides, as seen in this image of the coastal slope of the Arauco Peninsula.
Raised marine platform
A marine platform rose from the waters at Caleta Yani, on the Arauco Peninsula. Here, uplift was about 51 inches (130 centimeters), and killed almost all the mollusks and algae that live in the waters near the shore.
White fringe
The uplifted marine platform in Caleta Yani was covered in dead white algae after the earthquake.
Dichato, Chile
Studying how the earthquake moved the land is more than an academic curiosity. Chile is situated atop a hotspot for earthquake activity. Learning how this magnitude 8.8 quake moved the land will tell scientists more about what causes large earthquakes.
In this image, uplift is seen in the south part of the city of Dichato, home to 3,000 people.
Accessing the damage
The city of Dichato was one of the hardest hit by a tsunami that reached 33 feet (10 m) high, and washed more than 0.6 miles (1 kilometer) landward. An estimated 90 percent of the town was destroyed.
The new study that measured the land changes in this area is just one of many studies currently investigating the Chilean earthquake, which geophysicist Michael Bevis of Ohio State University said "will probably turn out to be one of the most important earthquakes ever in terms of scientific impact."
Natural Disasters: Top 10 U.S. Threats
Natural Disasters: Top 10 U.S. Threats
Credit: NASA via Ron Garan/Astro_RonGovernment officials are evaluating and revising disaster plans around the United States in the wake of Hurricane Katrina, just as they did after the Sept. 11 terrorist attacks. While war and automobiles kill more people than nature, find out what natural disasters top scientists' worry lists.
Pacific Northwest Megathrust Earthquake
Credit: Southern California Earthquake Data CenterGeologists know it's just a matter of time before another 9.0 or larger earthquake strikes somewhere between Northern California and Canada. The shaking would be locally catastrophic, but the biggest threat is the tsunami that would ensue from a fault line that's seismically identical to the one that caused the deadly 2004 tsunami in Indonesia.
New York Hurricane
Major hurricanes have made direct hits on the boroughs before, but the interval between them is so long that people forget, and officials fear they might not take evacuation orders seriously. The larger problem: It would take nearly 24 hours to make a proper evacuation of New York City, but hurricanes move more swiftly as they race north, so real warning time could be just a few hours
Asteroid Impact
Scientists can't say when the next devastating asteroid impact will occur. Odds are it won't be for decades or centuries, but an unknown space rock could make a sucker punch any time. Many experts say planning to deal with a continent-wide catastrophe should begin now.
Los Angeles Tsunami
Credit: National Oceanic and Atmospheric Administration (NOAA)An earthquake fault just off Southern California could generate a major quake and a $42 billion tsunami that would strike so fast many coastal residents would not have time to escape. Add to that the unprecedented destruction from the earthquake's shaking, and the situation would be reminiscent of Hurricane Katrina.
Supervolcano
It probably won't happen for hundreds or possibly even millions of years, but nobody really knows when Yellowstone will blow again, destroying life for hundreds of miles around and burying half the country in ash up to 3 feet (1 meter) deep.
Midwest Earthquake
.It has been nearly two centuries since a series of three magnitude-8 quakes shook the then-sparsely populated Midwest, centered near New Madrid, Missouri. Another big one is inevitable. Now the region is heavily populated, yet building codes are generally not up to earthquake snuff. What?s more, geology east of the Rockies causes quakes to be felt across a much wider region. Shelves would rattle from Boston to South Carolina. Some homes along the Mississippi would sink into oblivion.
Heat Waves
Heat waves kill more U.S. residents than any other natural disaster. As many as 10,000 people have died in past events. As urban areas get hotter, electricity systems are strained and the population ages, the risk grows.
East Coast Tsunami
Credit: nullIt seems no coast is immune to the threat of tsunami. For the Eastern United States, the likeliest scenario is waves kicked up by an asteroid splashing into the ocean. Astronomers already have their eye on one rock that could hit in the distant future, but the cosmos could hold a surprise, too.
Gulf Coast Tsunami
A fault line in the Caribbean has generated deadly tsunamis before. Up to 35 million people could be threatened by one in the not-to-distant future, scientists say.
Total Destruction of Earth
Okay, so nobody is spending too much time worrying about what to do if the planet is annihilated, but at least one person has seriously pondered whether and when it could happen. From being sucked into a black hole to being blown up by an antimatter reaction, there are scientifically plausible risks of an event that would render this whole list moot.http://www.livescience.comHuge Chilean Earthquake Raised Country's Coast
| Uplift of the ground is seen at the beach of Lebu. Uplift in this zone was about 71 inches (180 centimeters), which produced the uplift of a great marine platform. Credit: Science/AAAS |
The Chilean earthquake that struck on Feb. 27 changed the country’s landscape by raising the ground by more than 8 feet near the coast and sinking land farther inward, a new study finds.
Chile is situated atop a hotspot for earthquake activity, so learning how this magnitude 8.8 quake moved the land will tell scientists more about what causes large earthquakes.
The massive earthquake struck south-central Chile and was the fifth largest temblor ever recorded by modern seismology. A nearby part of Chile gave birth to the largest earthquake ever recorded — a magnitude 9.5 earthquake that struck in May 1960 and killed 5,700 people. Since 1973, 13 quakes of magnitude 7.0 or greater have hit the coastal country, according to the U.S. Geological Survey (USGS).
Scientists have now confirmed for the first time that the 2010 quake ruptured a long fault along the coast of Chile, and found that it raised land to a higher elevation in the south and sunk the Earth's surface in the North, according to the study.
To the scientists patrolling the coast, the change is obvious.
"You can just see the sea shells and sea weed hanging in the air, about head high," said Michael Bevis, a geophysicist at Ohio State University who was not involved with the study but has conducted his own studies of the Chilean coast. "You see all this stuff that belongs underwater is now up in the rocks."
Researchers found a white fringe formed by a kind of dead algae that is common along the Chilean coast. These normally pink algae are bleached by sunshine, and gave researchers a direct way to measure the grounds' uplift. [See images of Chile's raised coast]
Using the algae as a marker, the research team, led by Marcelo Farias at the University of Chile, found that the largest uplift was roughly 8.2 feet (2.5 meters) at the Arauco Peninsula. The uplift also shifted the coastline in some places 1,640 feet (500 m) toward the ocean.
Measuring how much the land sank was somewhat trickier. The researchers gauged sinking by measuring how high the water had risen on vegetation and manmade constructions like bridges. A 3.3 foot (1 m) drop in land was measured in some parts, but the study acknowledges some uncertainly about the subsidence level because of the difficulty in knowing the water levels before the quake hit, and exactly how these water levels changed after the quake.
Despite this uncertainty, the research team arrived at the site of the quake so quickly — taking measurements within a month of the rupture — that they were able to measure the sudden jump of the land that happens after an earthquake, Bevis said. This is important because the land continues to shift over time. Separating out the various ground movements is one step toward painting a picture of how the land moves during massive quakes.
The new study is just one of many studies currently investigating theChilean earthquake, which Bevis said "will probably turn out to be one of the most important earthquakes ever in terms of scientific impact."
"We've instrumented the crap out of the fifth biggest quake ever," Bevis told OurAmazingPlanet. "When we put this data together we're going to figure out what happened during and after the earthquake with an impressive level of detail."
Other movements around South America caused by the earthquake include:
- The Chilean city of Concepción moved at least 10 feet (3 meters) to the west.
- Buenos Aires, the capital of Argentina and across the continent from the quake's epicenter, moved about 1 inch (2.5 centimeters) to the west.
- Chile's capital, Santiago, moved about 11 inches (28 cm) to the west-southwest.
- The cities of Valparaiso and Mendoza, Argentina, northeast of Concepción, also moved significantly.
- http://www.livescience.com/
Chile Earthquake: Is Mother Nature Out of Control?
| earthquake Credit: |
Chile is on a hotspot of sorts for earthquake activity. And so the 8.8-magnitude temblor that shook the capital region overnight was not a surprise, historically speaking. Nor was it outside the realm of normal, scientists say, even though it comes on the heels of other major earthquakes.
One scientist, however, says that relative to a time period in the past, the Earth has been more active over the past 15 years or so.
The Chilean earthquake, and the tsunami it spawned, originated on a hot spot known as a subduction zone, where one plate of Earth's crust dives under another. It's part of the very active "Ring of Fire," a zone of major crustal plate clashes that surround the Pacific Ocean.
"This particular subduction zone has produced very damaging earthquakes throughout its history," said Randy Baldwin, a geophysicist with the U.S. Geological Survey (USGS).
The world's largest quake ever recorded, magnitude 9.5, occurred along the same fault zone in May 1960.
Even so, magnitude-8 earthquakes occur globally, on average, just once a year. Since magnitudes are given on a logarithmic scale, an 8.8-magnitude is much more intense than a magnitude 8, and so this event would be even rarer, said J. Ramón Arrowsmith, a geologist at Arizona State University.
Is Earth shaking more?
The Ryukyu Islands of Japan were hit with a 7.0-magnitude quake just last night. News of this, the Haiti quake and now Chile make it seem Earth is becoming ever more active. But in the grand scheme of things, geologists say this is just Mother Nature as usual.
"From our human perspective with our relatively short and incomplete memories and better and better communications around the world, we hear about more earthquakes and it seems like they are more frequent," Arrowsmith said. "But this is probably not any indication of a global change in earthquake rate of significance."
Coupled with better communication, as the human population skyrockets and we move into more hazardous regions, we're going to hear more about the events that do occur, Arrowsmith added.
However, "relative to the 20-year period from the mid 1970's to the mid 1990's, the Earth has been more active over the past 15 or so years," said Stephen S. Gao, a geophysicist at Missouri University of Science & Technology. "We still do not know the reason for this yet. Could simply be the natural temporal variation of the stress field in the earth's lithosphere." (The lithosphere is the outer solid part of the Earth.)
And while the Chilean earthquake wasn't directly related to Japan's 7.0-magnitude temblor, the two have some factors in common.
For one, any seismic waves that did make their way from Japan to the Chilean coast could play a slight role in ground-shaking.
"It is too far away for any direct triggering, and those distances also make the seismic waves as they would pass by from the Haiti or Japan events pretty small because of attenuation," Arrowsmith told LiveScience. (Attenuation is the decrease in energy with distance.) "Nevertheless, if the Chilean fault surface were close to failure, those small waves could push it even closer."
In addition, both regions reside within the Ring of Fire, which is a zone surrounding the Pacific Ocean where the Pacific tectonic plate and other plates dive beneath other slabs of Earth. About 90 percent of the world's earthquakes occur along this arc. (The next most seismic region, where just 5 to 6 percent of temblors occur, is the Alpide belt, which extends from the Mediterranean region eastward.)
Colliding plates
The Chilean earthquake occurred at the boundary between the Nazca and South American tectonic plates. These rocky slabs are converging at a rate of 3 inches (80 mm) per year, according to the USGS. This huge jolt happened as the Nazca plate moved down and landward below the South American plate. This is called a subduction zone when one plate subducts beneath another.
(Over time, the overriding South American Plate gets lifted up, creating the towering Andes Mountains.)
The plate movement explains why coastal Chile has such a history of powerful earthquakes. Since 1973, 13 temblors of magnitude 7.0 or greater have occurred there, according to the USGS.
In fact, today’s earthquake originated about 140 miles (230 km) north of the source region of the magnitude 9.5 earthquake of May, 1960, considered the largest instrumentally recorded earthquake in the world.
The 1960 earthquake killed 1,655 people in southern Chile, unleashing atsunami that crossed the Pacific and killed 61 people in Hawaii, Japan, and the Philippines.
In November 1922, a magnitude-8.5 earthquake occurred about 540 miles (870 km) to the north of the Feb. 27 earthquake, triggering a local tsunami that inundated the Chile coast and crossed the Pacific to Hawaii.
Because the recent one was such a huge earthquake, the shaking would likely have caused just as much damage had a similar-sized event occurred elsewhere, said Baldwin, the USGS scientist.
"If [the quake] were in Los Angeles you'd probably have massive destruction too," Baldwin said in a telephone interview.
Huge Chilean Earthquake Raised Country's Coast
| Uplift of the ground is seen at the beach of Lebu. Uplift in this zone was about 71 inches (180 centimeters), which produced the uplift of a great marine platform. Credit: Science/AAAS |
The Chilean earthquake that struck on Feb. 27 changed the country’s landscape by raising the ground by more than 8 feet near the coast and sinking land farther inward, a new study finds.
Chile is situated atop a hotspot for earthquake activity, so learning how this magnitude 8.8 quake moved the land will tell scientists more about what causes large earthquakes.
The massive earthquake struck south-central Chile and was the fifth largest temblor ever recorded by modern seismology. A nearby part of Chile gave birth to the largest earthquake ever recorded — a magnitude 9.5 earthquake that struck in May 1960 and killed 5,700 people. Since 1973, 13 quakes of magnitude 7.0 or greater have hit the coastal country, according to the U.S. Geological Survey (USGS).
Scientists have now confirmed for the first time that the 2010 quake ruptured a long fault along the coast of Chile, and found that it raised land to a higher elevation in the south and sunk the Earth's surface in the North, according to the study.
To the scientists patrolling the coast, the change is obvious.
"You can just see the sea shells and sea weed hanging in the air, about head high," said Michael Bevis, a geophysicist at Ohio State University who was not involved with the study but has conducted his own studies of the Chilean coast. "You see all this stuff that belongs underwater is now up in the rocks."
Researchers found a white fringe formed by a kind of dead algae that is common along the Chilean coast. These normally pink algae are bleached by sunshine, and gave researchers a direct way to measure the grounds' uplift. [See images of Chile's raised coast]
Using the algae as a marker, the research team, led by Marcelo Farias at the University of Chile, found that the largest uplift was roughly 8.2 feet (2.5 meters) at the Arauco Peninsula. The uplift also shifted the coastline in some places 1,640 feet (500 m) toward the ocean.
Measuring how much the land sank was somewhat trickier. The researchers gauged sinking by measuring how high the water had risen on vegetation and manmade constructions like bridges. A 3.3 foot (1 m) drop in land was measured in some parts, but the study acknowledges some uncertainly about the subsidence level because of the difficulty in knowing the water levels before the quake hit, and exactly how these water levels changed after the quake.
Despite this uncertainty, the research team arrived at the site of the quake so quickly — taking measurements within a month of the rupture — that they were able to measure the sudden jump of the land that happens after an earthquake, Bevis said. This is important because the land continues to shift over time. Separating out the various ground movements is one step toward painting a picture of how the land moves during massive quakes.
The new study is just one of many studies currently investigating theChilean earthquake, which Bevis said "will probably turn out to be one of the most important earthquakes ever in terms of scientific impact."
"We've instrumented the crap out of the fifth biggest quake ever," Bevis told OurAmazingPlanet. "When we put this data together we're going to figure out what happened during and after the earthquake with an impressive level of detail."
Other movements around South America caused by the earthquake include:
- The Chilean city of Concepción moved at least 10 feet (3 meters) to the west.
- Buenos Aires, the capital of Argentina and across the continent from the quake's epicenter, moved about 1 inch (2.5 centimeters) to the west.
- Chile's capital, Santiago, moved about 11 inches (28 cm) to the west-southwest.
- The cities of Valparaiso and Mendoza, Argentina, northeast of Concepción, also moved significantly.
- http://www.livescience.com
Amazing Images: Volcanoes from Space
Klyuchevskaya Volcano
The snow-covered Klyuchevskaya Volcano on Russia's Kamchatka Peninsula part of the highly volcanically and seismically active Pacific "Ring of Fire." Klyuchevskaya the largest active volcano in the Northern Hemisphere is seen here erupting in March 2010.
The volcanic plume, low-lying clouds and snow are all white in the image taken by NASA's Earth Observing-1 satellite, while a lava flow on the shadowed (northern) flank of the mountain is nearly black.
The 15,863-foot (4,835-meter) high volcano has erupted nearly continuously since it first formed about 6,000 years ago.
The volcanic plume, low-lying clouds and snow are all white in the image taken by NASA's Earth Observing-1 satellite, while a lava flow on the shadowed (northern) flank of the mountain is nearly black.
The 15,863-foot (4,835-meter) high volcano has erupted nearly continuously since it first formed about 6,000 years ago.
Anak Krakatau
Anak Krakatau ("Son of Krakatau") is the volcanic island that formed in the caldera of Krakatau (also written Krakatoa), which erupted catastrophically in 1883. It sits in the Sunda Strait between the Indonesian islands of Java and Sumatra.
That massive eruption spewed huge amounts of ash and pumice into the sky and could be heard thousands of miles away. Tsunamis spawned by the eruption inundated nearby parts of Indonesia, killing some 36,000 people one of the most devastating eruptions in history.
Anak Krakatau arose less than 50 years after the 1883 eruption and has seen frequent rumblings and outbursts since then.
That massive eruption spewed huge amounts of ash and pumice into the sky and could be heard thousands of miles away. Tsunamis spawned by the eruption inundated nearby parts of Indonesia, killing some 36,000 people one of the most devastating eruptions in history.
Anak Krakatau arose less than 50 years after the 1883 eruption and has seen frequent rumblings and outbursts since then.
Eyjafjallajökull Volcano
Eyjafjallajökull began pumping ash into the atmosphere on March 20, 2010. As the plume was blown across Europe, it severely hampered air travel while it also produced spectacularly red sunsets.
How long Eyjafjallajökull will continue to erupt for is up in the air, though in the past a single eruption has lasted for years. The inter-connected magma chambers of many of Iceland's volcanoes give them a unique dynamic, and Eyjafjallajökull connects to another nearby volcano, Katla, which has a history of erupting not long after its neighbor.
The volcanoes of Iceland are what created the island about 70 million years ago. The small European nation is situated on the Mid-Atlantic Rise, a seam in the Earth's surface under the North Atlantic Ocean where the Eurasian and North American plates slide apart. Magma upwells along the rise and spreads out to create new crust. Iceland is thought to sit on a pocket of magma that created the island and continues to fuel its many volcanoes today.
How long Eyjafjallajökull will continue to erupt for is up in the air, though in the past a single eruption has lasted for years. The inter-connected magma chambers of many of Iceland's volcanoes give them a unique dynamic, and Eyjafjallajökull connects to another nearby volcano, Katla, which has a history of erupting not long after its neighbor.
The volcanoes of Iceland are what created the island about 70 million years ago. The small European nation is situated on the Mid-Atlantic Rise, a seam in the Earth's surface under the North Atlantic Ocean where the Eurasian and North American plates slide apart. Magma upwells along the rise and spreads out to create new crust. Iceland is thought to sit on a pocket of magma that created the island and continues to fuel its many volcanoes today.
Mount Etna
Here, Sicily's Mount Etna Italy's most active volcano sits mostly quiet in March 2010, though thin brown and white plumes rise above the Central Crater (also known as Bocca Nuova) and the Northeast Crater.
This shield volcano rises 10,925 feet (3,330 meters) high and has one of the longest documented records of eruption, dating back to 1500 B.C.
Etna's last eruption ended in June 2009, according to the Istituto Nazionale di Geofisica e Vulcanologia Sezione di Catania.
This shield volcano rises 10,925 feet (3,330 meters) high and has one of the longest documented records of eruption, dating back to 1500 B.C.
Etna's last eruption ended in June 2009, according to the Istituto Nazionale di Geofisica e Vulcanologia Sezione di Catania.
Kilauea's Halema'uma'u Crater
lava-filled pit set inside Kilauea's Halema'uma'u Crater emitted a plume of steam, ash and sulfur dioxide earlier this year as seen in this image from NASA's Earth-Observing-1 satellite.
Halema'uma'u Crater is itself a crater in the larger Kilauea Caldera the smaller pit opened up in its southwestern wall on March 19, 2008. Volcanic emissions have continued almost uninterrupted since, punctuated occasionally by violent explosions of ash and fragments of rock torn from the crater walls.
On September 5, 2008, scientists at the Hawaii Volcano Observatory discovered a lava lake inside the pit.
Halema'uma'u Crater is itself a crater in the larger Kilauea Caldera the smaller pit opened up in its southwestern wall on March 19, 2008. Volcanic emissions have continued almost uninterrupted since, punctuated occasionally by violent explosions of ash and fragments of rock torn from the crater walls.
On September 5, 2008, scientists at the Hawaii Volcano Observatory discovered a lava lake inside the pit.
Mount St. Helens
Mount St. Helens blew in a cataclysmic eruption on May 18, 1980. That eruption blew ash high into the atmosphere, where it was picked up and carried for thousands of miles.
The eruption killed 57 people and devastated the local landscape, which is still recovering more than 30 years later. During the eruption, the north flank of the volcano slid away in the largest landslide in recorded history.
The Mount St. Helens eruption taught scientists much about looking for warning signs of eruptions at it and other volcanoes. The volcano rumbled back to life in 2004, though the eruptions from that episode were far milder than the 1980 disaster.
The eruption killed 57 people and devastated the local landscape, which is still recovering more than 30 years later. During the eruption, the north flank of the volcano slid away in the largest landslide in recorded history.
The Mount St. Helens eruption taught scientists much about looking for warning signs of eruptions at it and other volcanoes. The volcano rumbled back to life in 2004, though the eruptions from that episode were far milder than the 1980 disaster.
Jebel at Tair
Jebel at Tair, a small volcanic island in the Red Sea, erupted in late September 2007. A plume of smoke from the volcano was caught in this Nov. 8, 2007 image taken by NASA's EO-1 satellite.
The dark stains on the volcano's slopes are evidence of earlier lava flows.
This stratovolcano sits midway between Yemen and Eritrea and is made up of alternating layers of hardened lava, solidified ash and rocks ejected from eruptions.
The dark stains on the volcano's slopes are evidence of earlier lava flows.
This stratovolcano sits midway between Yemen and Eritrea and is made up of alternating layers of hardened lava, solidified ash and rocks ejected from eruptions.
Submarine Eruption in Tonga Islands
This submarine eruption, captured by NASA's Aqua satellite, occurred in the Tonga Islands of the South Pacific in mid-March 2009.
The area around the eruption appears bright blue-green, likely resulting from ash and other volcanic debris suspended in the water. The brilliant white patch may result from vapor released by the volcano.
Northwest of the eruption, a ribbon of brown is likely a pumice raft pumice is highly porous and floats on water. When a lot of pumice if thrown from an erupting volcano it can bunch together into a "raft." Just such a raft occurred after an August 2006 eruption.
The area around the eruption appears bright blue-green, likely resulting from ash and other volcanic debris suspended in the water. The brilliant white patch may result from vapor released by the volcano.
Northwest of the eruption, a ribbon of brown is likely a pumice raft pumice is highly porous and floats on water. When a lot of pumice if thrown from an erupting volcano it can bunch together into a "raft." Just such a raft occurred after an August 2006 eruption.
Ol Doinyo Lengai
Ol Doinyo Langai in Tanzania is the only volcano in the world that erupts what is called natrocarbonatite lava, which is rich in calcium, sodium and potassium, but low in silica (silicon dioxide).
>The lava of Ol Doinyo Lengai is extremely cool (932 to 1,112 degrees Fahrenheit, or 500 to 600 degrees Celsius, compared to 2,120 F, or 1,160 C, for typical basaltic lava) and relatively fluid.
The volcano switches from periods where it erupts liquid lava that pools into lava lakes to explosive periods where it builds large ash cones. In the image, acquired with NASA's Earth-Observing-1 satellite, dark areas on the crater floor are recent lava flows (days to weeks old), while the beige and white regions are older lava that has reacted with rain and moisture in the atmosphere.
>The lava of Ol Doinyo Lengai is extremely cool (932 to 1,112 degrees Fahrenheit, or 500 to 600 degrees Celsius, compared to 2,120 F, or 1,160 C, for typical basaltic lava) and relatively fluid.
The volcano switches from periods where it erupts liquid lava that pools into lava lakes to explosive periods where it builds large ash cones. In the image, acquired with NASA's Earth-Observing-1 satellite, dark areas on the crater floor are recent lava flows (days to weeks old), while the beige and white regions are older lava that has reacted with rain and moisture in the atmosphere.
Manam Volcano
Manam volcano is one of Papua New Guinea's volcanoes. In this June 28, 2009, image, a faint plume rises from the volcano.
Manam is a stratovolcano that measures 6 miles (10 kilometers) across. Frequent historical eruptions, typically of fairly mild character, have been recorded at Manam since 1616, according to the Smithsonian's Global Volcanism Program.
Eruptions from the volcano have caused casualties, including 13 deaths from a pyroclastic flow in December 1996, and four deaths from a mudflow in March 2007. Large eruptions in late 2004 forced the evacuation of the entire island.
Manam is a stratovolcano that measures 6 miles (10 kilometers) across. Frequent historical eruptions, typically of fairly mild character, have been recorded at Manam since 1616, according to the Smithsonian's Global Volcanism Program.
Eruptions from the volcano have caused casualties, including 13 deaths from a pyroclastic flow in December 1996, and four deaths from a mudflow in March 2007. Large eruptions in late 2004 forced the evacuation of the entire island.
Turrialba Volcano
A translucent plume of smoke rises from Turrialba Volcano, located in central Costa Rica.
The 10,960-foot (3,340-meter) summit of the volcano appears grey and brown in this image taken by NASA's Earth-Observing-1 satellite because it is barren. Five major explosive eruptions have occurred at Turrialba during the past 3,500 years.
While much of the forest and fields around the volcano appear a verdant green, some vegetation shows signs of damage. Since 2007, frequent acid rain showers caused by activity at the volcano have killed or damaged much of the vegetation to the southwest of the summit, leaving the area brown and orange.
The 10,960-foot (3,340-meter) summit of the volcano appears grey and brown in this image taken by NASA's Earth-Observing-1 satellite because it is barren. Five major explosive eruptions have occurred at Turrialba during the past 3,500 years.
While much of the forest and fields around the volcano appear a verdant green, some vegetation shows signs of damage. Since 2007, frequent acid rain showers caused by activity at the volcano have killed or damaged much of the vegetation to the southwest of the summit, leaving the area brown and orange.
Minchinmávida and Chaitén Volcanoes
The Chaitén and Minchinmávida Volcanoes lie in the Andes Mountains, along the western coast of South America, which is host to numerous volcanoes. The volcanoes were created by, and are still fueled by, the magma generated as the Nazca tectonic plate subducts under the South American plate.
The two volcanoes shown in this photo taken by an astronaut aboard the International Space Station lie near the southern boundary of the NazcaSouth America subduction zone in southern Chile.
Charles Darwin observed an eruption of Minchinmávida during his Galapagos Islands voyage in 1834. The volcano's last recorded eruption took place the following year.
Chaitén has erupted more recently - it roared to life unexpectedly on May 2, 2008, generating dense ash plumes and forcing the evacuation of the nearby town of Chaitén. Volcanic activity continued at Chaitén in early 2009; several days before this astronaut photograph was taken, a new lava dome partially collapsed and generated a pyroclastic flow (a scalding avalanche of gas, ash, and rock debris).
The two volcanoes shown in this photo taken by an astronaut aboard the International Space Station lie near the southern boundary of the NazcaSouth America subduction zone in southern Chile.
Charles Darwin observed an eruption of Minchinmávida during his Galapagos Islands voyage in 1834. The volcano's last recorded eruption took place the following year.
Chaitén has erupted more recently - it roared to life unexpectedly on May 2, 2008, generating dense ash plumes and forcing the evacuation of the nearby town of Chaitén. Volcanic activity continued at Chaitén in early 2009; several days before this astronaut photograph was taken, a new lava dome partially collapsed and generated a pyroclastic flow (a scalding avalanche of gas, ash, and rock debris).
Tsunami-Causing Earthquake Trimmed Bulge off Earth's Middle
The Dec. 26 earthquake off the coast of Indonesia was the fourth largest in one hundred years.? Scientists have determined that this major shift in the Earth's plates changed the planet's shape - enough to shorten the day by fractions of a second and to shift the North Pole by an inch.
The general shape of the Earth is slightly oblate - that is, it is not a perfect sphere but is slightly squished down, making it about 26 miles wider at the equator than between the poles.? This shape, however, is not rigid, with climate being a major distorting force.??
But the magnitude nine earthquake last month almost certainly altered the shape as well.? Recent calculations have estimated that this catastrophic land displacement caused a small reduction in the bulge, making the planet more round.
The waistline was reduced by not quite a millimeter because of the earthquake," said Benjamin Fong Chao from NASA's Goddard Space Flight Center.
This slimming down sped up the rotation of the Earth, much like when a spinning ice skater pulls in her arms to increase her speed.? The length of the day correspondingly decreased by 2.68 millionths of a second.?
No watches need to be changed because of this.? In fact, Chao toldLiveScience in a telephone interview that this change is too small for current detection methods.? But, he said, the change in the Earth's shape and pole location might be observable, once all the relevant data is reviewed.
Crash Diet
Chao and his colleague, Richard Gross of NASA's Jet Propulsion Laboratory, have analyzed seismological data from 20,000 earthquakes with magnitudes greater than five.? They have modeled how each has affected the shape of the Earth, and subsequently the rotation.?
In two thirds of the cases, the planet has become less oblate, or skinnier, following a temblor.? The other one third of the time, the planet has become more oblate.??
None of these changes, however, were big enough to directly measure - until maybe now.
"The Earth got hit pretty hard on December 26," Chao said.? "For the first time, we hope to see the effect of an earthquake, but it will take a couple of months to sort through the data."?
The Earth's profile can be measured with satellite laser ranging (SLR).? By precisely tracking the orbit of a satellite, scientists can infer the gravitational pull from that part of Earth below the satellite.?
"We measure the gravity change, and from that, we infer the shape change," said Minkang Cheng from the University of Texas at Austin.
Seeing the effect of the earthquake, though, will be difficult because there are other processes that cause greater distortions.?
Cheng and his co-worker, Byron D. Tapley, have analyzed 28 years of SLR data, identifying several cyclical patterns in the variations of the Earth's oblateness, which they have correlated with weather and climate changes.
The amplitudes of these cycles are 10 times bigger than the expected change from the earthquake.
"There's no question that a signal [from the earthquake] is there in the satellites, but it is very tough to separate this from the climate-induced signal," Tapley said.
The Weight of Water
One of the largest variations in the SLR data is a seasonal "breathing" in and out.? On average, the Earth's shape fluctuates by 2.38 centimeters over the course of a year, Cheng said.?
The cause of this annual shift is the redistribution of water.? Evaporation over the ocean leads to precipitation over land, which eventually makes its way back to the ocean.? Major climate changes can alter this water cycle.
"The magnitude of that mass transport of water varies from year to year."? Tapley said.? "The change is very dramatic in El Nino years."??
Cheng and Tapley found that every 4-6 years the Earth becomes slightly more oblate - by about 0.7 centimeters - due to the redistribution of precipitation caused by an El Nino event.?
"Essentially, El Nino puts more moisture in the lower latitudes," Tapley said.
Tapley and Cheng plan to look at how other climate changes - specifically global warming - may affect the Earth's shape in their next paper.
The Weight of Ice
There is one other interesting variation in the SLR data due to the effects of the last ice age, called the postglacial rebound (PGR).?
Ten thousand years ago, when parts of the continents were covered in ice, that weight deformed the earth by squeezing down on the poles.? When the ice melted, the land did not immediately pop back into place but is even now still recovering.?
That recovery has the Earth becoming less and less oblate - at a rate of about a tenth of a centimeter per year, according to Cheng.?
Chao said that the PGR also shifts the direction of the North Pole by about four inches a year.? Since this is only four times bigger than the expected shift from the earthquake, Chao believes this is the best hope for measuring the earthquake's effect.
Potential Southern California Tsunami Could Cost Up to $42 Billion
The warning system covering the Pacific Ocean might save many lives if a tsunami strikes Southern California. But nothing can stop the destruction.
A new study puts the price tag for a worst-case scenario at $42 billion, and that does not include billions of dollars in additional damage caused directly by an earthquake that is pegged as the likely source of a potentially devastating tsunami.
Waves could inundate parts of the ports of Los Angeles and Long Beach. Many beach cities and smaller communities in Los Angeles and Orange County would suffer.
And there might not be enough time for a warning to be very useful.
The one-minute warning
The scientists say an underwater landslide just offshore, triggered by an earthquake, could generate a tsunami whose tallest waves would arrive "only one minute after the slide."
Other studies have the Pacific Northwest could be hit swiftly by devastating tsunamis, too. And researchers recently warned of a similar danger to Gulf Coast states. Prior to the tsunami last December, other geologists warned of the risk of mega-tsunamis around the entire Pacific basin from underwater landslides.
The new research was done by geologists, tsunami experts, engineers and urban planners at the University of Southern California. It is detailed in April edition of Civil Engineering magazine.
The group cites recent studies that suggest a large earthquake under the ocean off Los Angeles is likely at some point in the future. And it does not take a 9.0 "great quake," such as the one last December in Indonesia, to do the trick. A magnitude 7.0 earthquake near Papua New Guinea in 1998 generated deadly waves thought to be caused by a submarine landslide, which the earthquake triggered.
"The shaking from an earthquake of magnitude 7 or greater on an offshore thrust or reverse fault would undoubtedly be damaging to coastal communities [in Southern California], and its effect could be greatly magnified if it were to generate a tsunami," the scientists write.
Repeating history
The conclusions draw on evidence from several locally generated small tsunamis that have been recorded over the past 200 years. A Santa Barbara earthquake in 1812 spawned a moderate tsunami that affected more than 37 miles (60 kilometers) of coastline. Evidence of prehistoric events suggest submarine slumps that could have generated tsunamis up to 66 feet (20 meters) tall.
"There will be others," the researchers say, though of course they don't know when or how tall any tsunami might be.
Various scenarios in the study generate loss estimates of between $7 billion and $42 billion directly related to the tsunami. Costs include direct damage as well as the economic costs of lost shipping opportunities and traffic delays owing to damaged freeways.
"We chose not to model fatalities because we were being deliberately conservative, and because we wanted to avoid contentious assumptions about the economic value of life," said study member James Moore II. "The Papua New Guinea tsunami of 1998 was generated by a mechanism similar to the one modeled here, and that event cost over 2,000 lives. The toll here could be much higher."
New Method Promises Better Earthquake Prediction
| An ocean bottom seismometer, or OBS, like this one will be deployed in 2007 on the East Pacific Rise. Credit: Woods Hole Oceanographic Institution |
Predicting major earthquakes, at least the type that produce tsunamis, may get a little easier with knowledge gleaned from a new study of past events.
By monitoring small seismic shocks on the ocean floor, scientists may be able to generate an "undersea earthquake forecast." The forecast would alert seismologists of an impending earthquake hours, or even minutes, before it strikes.
In general, earthquake prediction is a very challenging task. Though a lot of research has gone into the problem, no firm prediction ability exists. The best geologists can do is foresee events likely to occur along a certain fault in coming months or years.
"Some scientists believe that earthquakes come on suddenly with no warning signs, and the big ones are therefore unpredictable," said Thomas Jordan of the University of Southern California Earthquake Center. But in some parts of the ocean, Jordan maintains, predictions appear possible.
In fact, Monday's 8.7-magnitude earthquake was predicted by one group of scientists. Yet it did not cause the tsunami many experts expected. Researchers are puzzled as to why, and the whole event illustrates the challenges of forecasting.
Looking backJordan and his co-researchers studied data gathered from past earthquakes occurring along five faults on the East Pacific Rise - a region whose tectonic plates are spreading apart at a rate of five inches a year.
They defined a "foreshock" as any shaking of at least a magnitude 2.5, and the main shock of a temblor as being a 5.4 event or greater. To generate a hypothetical foreshock "alert," they looked for rumblings occurring within a 10-mile radius of the quake's eventual epicenter within the hour before the actual quake struck.
Using this model, six of the nine major quakes along the East Pacific Fault from 1996 to 2001 could have successfully predicted, the researchers wrote in the March 24 issue of the journal Nature.
This method of predicting quakes is not as useful for land earthquakessince they are generally not preceded by these types of foreshocks, other research indicates.
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Better instrumentation on the seafloor could lead to better predictions.
Looking aheadWork remains before any official predictions could be made. And questions remain about the fickle nature of Earth's shifting crust, which does not behave the same in the various spots where broken plates meet.
"If both foreshocks and mainshocks are triggered by an earlier event, which could be a gradual slipping along a fault line, technically known as an aseismic slow slip transient that doesn't create seismic waves, then it could be detected with the right instruments," said Jeffrey McGuire of the Woods Hole Oceanographic Institution and coauthor of the paper on the study.
Scientists have detected deep sea slow slip transients in subduction zones, where one tectonic plate is shoved under another. Such events have been detected off Japan and along the Cascadia Fault off the Pacific Northwest, but these events did not trigger massive earthquakes.
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Large networks of sensors, like those in place on the San Andreas Fault, can detect these slow-moving events. Now scientists want to set up a similar system on undersea faults.
McGuire will head an expedition in 2007 to place new sensors on the East Pacific Rise. Seismologists believe that an extensive network of sensors on the ocean floor may help spot a brewing undersea earthquake.
Tsunami-Generating Earthquake Near U.S. Possibly Imminent
| The tsunami of April 1, 1946 broke over Pier No. 1 in Hilo Harbor, Hawaii. The man in the foreground (lower left) became one of the 159 deaths on the islands. Credit: NOAA |
There are only two places in the United States where colliding tectonic plates could cause a major tsunami, and new studies show a new earthquake in at least one of these locations could be imminent.
The Cascadia subduction zone, a 680-mile fault that runs 50 miles off the coast of the Pacific Northwest -- from Cape Mendocino in California to Vancouver Island in southern British Columbia -- has experienced a cluster of four massive earthquakes during the past 1,600 years. Scientists are trying to figure out if it is about to undergo a massive shift one more time before entering a quiescent period.
"People need to know it could happen," said U.S. Geological Survey geologist Brian Atwater.
The historical record for this zone, which has the longest recorded data about its earthquakes of any major fault in the world, shows that earthquakes occur in clusters of up to five events, with an average time interval of 300 years between quakes, said Chris Goldfinger, a marine geologist at Oregon State University. Goldfinger and other scientists have been studying this subduction zone for many years.
The two most recent quakes on this fault occurred in the year 1700 (a magnitude 9 event) and approximately the year 1500. It has now been 305 years since the last event. So is the Cascadia subduction zone finished for now or on the brink of event number five?
"We know quite a bit about the periodicity of this fault zone and what to expect," he said. "But the key point we don't know is whether the current cluster of earthquake activity is over yet, or does it have another event left in it."
 At the Cascadia subduction zone, an oceanic tectonic plate called the Juan de Fuca is pulled and driven (subducted) beneath the continental North American plate, setting up conditions for undersea "megathrust" earthquakes. |
The Cascadia subduction zone occurs where the relatively thin Juan de Fuca plate moves eastward and under the westward-moving North American Plate. When that collision results in a rupture, massive earthquakes occur. The other active subduction zone capable of producing a major earthquake-tsunami sequence is in Alaska, the site of a giant earthquake and subsequent tsunami in 1964.
Scientists say a rupture along the Cascadia fault would cause the sea floor to bounce 20 feet or more, setting off powerful ocean waves relatively close to shore. The first waves could hit coastal communities in 30 minutes or less -- too rapidly for the current warning systems to save lives.
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A tsunami along the Atlantic Coast is considered extremely unlikely.
Tsunamis are the result of sudden rises or falls in a section of the earth's crust under or near the ocean, usually caused by earthquakes, volcanic activity or landslides. Earthquakes at subduction zones (rather than at other types of faults such as thrust faults) produce the highest energy tsunamis, especially when they occur in deep water. The seismic activity displaces sea water, creating a rise or fall in the level of the ocean above. This rise or fall in sea level initiates the formation of a tsunami wave. The wave's height increases in shallower water.
Geologists can track earthquakes back in time by radiocarbon dating deposits of sand called turbidites, which come from undersea landslides.
Major studies on the Cascadia fault zone have identified 19 to 21 major earthquake events during the past 10,000 years. During at least 17 of these events, the entire fault zone probably ruptured at once, causing an earthquake around magnitude 9 and major tsunamis, such as those which savaged East Asia last week.
The Asian event happened where the India plate was subducted beneath the Burma microplate. It ruptured, for the first time since 1833, along a 600-mile front just about the same length as the Cascadia Subduction Zone.
The Asian event may provide a shocking demonstration of the geologic future of the Pacific Northwest, Goldfinger said. For hundreds of years, subduction zone plates remain locked in place, releasing little tension. Every few centuries, in a few minutes of violence, forces are released as the upper plate moves seaward, producing a massive tsunami following earthquake shaking.
"In the case of the Cascadia Subduction Zone, you could have an area of ocean floor that's 50 miles wide and 500 to 600 miles long suddenly snap back, causing a huge tsunami," Goldfinger said. "At the same time, we could expect some parts of the upper, or North American, plate to sink one to two meters. These are massive tectonic events. Subduction zones produce the most powerful earthquakes and tsunamis in the world."
The question is not whether, but when the Cascadia Subduction Zone will break again.
"One possibility is that we could be done with this cluster and looking at a period of many hundreds of years before the next earthquake," Goldfinger said. "The other distinct possibility is we could still be in a cluster of events. If that's the case, the average time interval between earthquakes within a cluster is already up. We would be due just about any day."'
Tracking a Retreating Glacier
Columbia Glacier
Scientists set up camp where the Columbia Glacier meets the ocean in this photo from August 2009. The scientists' orange tents are seen on the cliff in the lower left-hand corner of the image.
Glacier Camp
Only accessible by helicopter, three to five scientists will spend up to a month camped out on the wet terrain surrounding the glacier. They deploy instruments to measure the glaciers, take photographs and make observations in the field. The instruments do not transmit their data back to the lab, so twice a year scientists trek to Columbia to retrieve it.
Iceberg are born
Scientists captured a dramatic submarine iceberg calving at the grounded end of the Columbia Glacier on June 17, 2005. The height of the ice cliff is roughly 230 feet (70 meters).
Service Call
Glaciologist O'Neel of the USGS is pictured here checking up on the seismometer that measured the activity of the Columbia Glacier in May 2009.
"Think of a calving event kind of like a little earthquake," O'Neel told OurAmazingPlanet. "Seismometers tell us when and how long it took to break off, and also gives us ideas about how it was created."
"Think of a calving event kind of like a little earthquake," O'Neel told OurAmazingPlanet. "Seismometers tell us when and how long it took to break off, and also gives us ideas about how it was created."
Conveyor Belt of Ice
Tad Pfeffer is seen photographing the Columbia Glacier from the western boundary in June 2005. The scientists do more than just take pretty pictures. Try also make quantitative measurements with their images. Pictures taken with this camera help scientists calculate how fast the ice is flowing and also measure the glacier's geometry.
Time-Lapse Photography
Adam LeWinter is servicing one of the time-lapse cameras at Columbia Glacier. Time-lapse images provide one of the primary sources of data used in this study.
"We use them to identify times when large calving events occur and then look at the seismic data during those periods to study the fracture process," O'Neel said.
In 2004, the time-lapse cameras took four to six pictures per day. Today they snap photographs every 20 minutes.
"We use them to identify times when large calving events occur and then look at the seismic data during those periods to study the fracture process," O'Neel said.
In 2004, the time-lapse cameras took four to six pictures per day. Today they snap photographs every 20 minutes.
The Megatsunami: Possible Modern Threat
| The Megatsunami: Possible Modern Threat Credit: |
SAN FRANCISCO -- Volcanic landslides that generate huge and devastating tsunamis tend to occur during historically warmer times on Earth, a new study suggests. Scientists don't know exactly why, but since the global climate is warming as you read this, the apparent connection was tossed out this week as a reason for scientists to be concerned about the threat now.
Tsunamis are waves that race across the ocean without much fanfare but grow to frightening proportions when they reach land. The waves are deep, and while they may appear just a few inches or feet tall on the open ocean, they can soar to the height of a multi-story building as they are forced upward near the shore.
A tsunami can be generated by the sudden uplift of the seafloor in an earthquake, or by the paddle-like effect of a landslide crashing into the sea from, say, an island volcano. Yet while quake-generated tsunamis have been observed from their genesis to the disastrous end, scientists have never witnessed a significant open-ocean tsunami generated by a landslide.
Evidence exists at various locations around the world for megatsunamis, as scientists call the largest of these events. They seem to occur every 100,000 years or so, said Gary McMurtry of the University of Hawaii.
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These monsters can be hundreds of feet tall and, depending on local topography, race miles inland.
One controversial event, about 110,000 years ago, appeared to create a 1,600-foot wave in Hawaii. Yes, you read that right: Nearly one-third of a mile, or about half a kilometer.
But the evidence -- marine fossils way up there where there's no sea -- is controversial. Perhaps the islands have been rising and carried the fossils up, critics suggest.
McMurtry's team looked at marine fossils at the Kohala volcano on the main island of Hawaii, which is known to be sinking about an inch per decade. The fossils simply could not have started at a lower elevation, McMurtry said Monday at a meeting of the American Geophysical Union held here. A submarine landslide from the giant Mauna Loa volcano has been dated to the same time and, the thinking goes, caused the tsunami.
McMurtry and his colleagues also re-examined evidence for a tsunami that may have struck Bermuda and other locations in the Atlantic 420,000 years ago.
Scientists agree that submarine landslides caused by the collapse of island volcanoes -- think of the destruction of Mount St. Helens -- could generate these megatsunamis. Evidence for such landslides can be found in topography scans of seafloors around various island volcanoes, McMurtry points out.
"These giant landslides seem to occur during periods of higher than normal sea level -- like we have now," he said.
High sea levels tend to correspond with wetter climates, he said. What this has to do with landslides is not known. But perhaps, McMurtry figures, excess rainfall can serve as a trigger for the cleaving of a volcano-in-waiting.
That might all sound like a lot of logic leaps, and McMurtry is the first to admit there isn't enough data to figure out whether global warming and tsunamis are correlated. But there is some independent thinking that supports the notion.
Peter Cervelli, of the Alaska Volcano Observatory, has studied the Hawaiian volcanoes and is not involved in McMurtry's work. Cervelli said it's possible that water during extended wet periods seeps down into natural faults on the flanks of a volcano -- volcanoes are known to be more porous than other land areas -- precipitating a collapse by "bringing it closer to failure."
And in other work, Emily Brodsky of the University of California, Los Angeles has modeled the friction involved in huge volcanic landslides. She agrees that it's possible that higher rainfall amounts could make a precarious situation more slippery.
So should we worry? "Maybe," says McMurtry. He thinks that a tsunami, which can race across an entire ocean in a matter of hours, is a real threat to urbanized coastlines. Other experts agree that a large tsunami would be bad news for, say, Los Angeles or New York City. And tsunamis are not parochial. One originating in Alaska in 1964 killed people in California and generated damaging surges clear down in Chile.
McMurtry believes the threat is greater than from an asteroid impact, but asteroid research has managed to lure more funding. More money should be spent to monitor the stability of oceanic volcanoes, McMurtry argues.
"Mauna Loa is as big as it's ever been, so the energy is there" for a giant submarine landslide, McMurtry said. He's even attached some odds to the threat: "The probability of a megatsunami in Hawaii in the next 10,000 years is about 50 percent."
