Researchers have documented six major volcanic eruptions in Sumatra over the past 35,000 years – most equaling or surpassing in explosive intensity the eruption of Washington's Mount St. Helens in 1980. "Sumatra has a number of active and potentially explosive volcanoes and many show evidence of recent activity. Most of the eruptions are small, so little attention has been paid to the potential for a catastrophic eruption. But our study found some of the first evidence that the region has a much more explosive history than perhaps has been appreciated."
Until this study, little was known about Sumatra's volcanic history – in part because few western scientists have been allowed access to the region. The most visible evidence of recent volcanic activity among the estimated 33-35 potentially active volcanoes are their steep-sided cones and lack of vegetation, indicating at least some minor eruptive processes. But in 2007, an expedition was permitted into the region and the researchers set out to explore the earthquake history of the region by studying sediment cores from the Indian Ocean. While searching the deep-sea sediment cores for "turbidites" – coarse gravel deposits that can act as a signature for earthquakes – they noticed unmistakable evidence of volcanic ash and began conducting a parallel investigation into the region's volcanic history.
"The ash was located only in certain cores, so the activity was localized. Yet the eruptions still were capable of spreading the ash for 300 kilometers or more, which gave us an indication of how powerful the explosive activity might have been." They found evidence of six major eruptions and estimated them to be at least from 3.0 to 5.0 on the Volcanic Explosivity Index. Mount St. Helens, by comparison, was 5.0.
The Indian Ocean region is certainly known to have a violent volcanic history. The 1883 eruption of Krakatoa between Sumatra and Java is perhaps the most violent volcanic explosion in recorded history, measuring 6.0 on the VEI and generating what many scientists believe to have been one of the loudest noises ever heard on Earth. Sumatra's own Toba volcano exploded about 74,000 years ago, generating a major lake – not unlike Oregon's own Crater Lake, but much larger. "It looks like a giant doughnut in the middle of Sumatra." umatra's volcanoes occasionally belch some ash and smoke, and provide comparatively minor eruptions, but residents there may not be fully aware of the potential catastrophic nature of some of its resident volcanoes. "Prior to 2004, the risk from a major earthquake were not widely appreciated except, perhaps, in some of the more rural areas. And earthquakes happen more frequently than major volcanic eruptions. If it hasn't happened in recent memory…"
The next step in the research is to work with scientists from the region to collect ash and volcanic rock from the island's volcanoes, and then match their chemical signature to the ash they discovered in the sediment cores. "Each volcano has a subtly different fingerprint, so if we can get the terrestrial data, we should be able to link the six major eruptions to individual volcanoes to determine the ones that provide the greatest risk factors."
as you would have those upstream do unto you.**
Wendell Berry
LARGEST QUAKES -
Live Seismograms - Worldwide (update every 30 minutes)
This morning -
None 5.0 or higher.
Yesterday -
5/16/12 -
5.0 SOUTHERN ALASKA
5.2 SOUTH OF TONGA
5.8 NEW BRITAIN REGION, P.N.G.
Chile - The magnitude-6.2 magnitude earthquake that hit on Monday damaged walls, shattered windows and knocked out electricity in parts of far-northern Chile and the Peruvian city of Tacna but no injuries or major damage were reported. The quake, which occurred at 6 a.m. local time (6 a.m. EDT; 1000 GMT), was centered 66 miles (107 kilometers) northeast of the city of Arica 98 kilometers (61 miles) underground. It was also felt in the Peruvian city of Arequipa and in the Bolivian capital of La Paz, 120 miles (200 kilometers) away. Some neighborhoods in Tacna, a city of 200,000 66 kilometers (44 miles) from the epicenter, suffered brief power outages. Broken windows and rocks shook loose onto highways.
The Chilean government emergency agency said about 250 people fled into the streets of Arica when the shaking started, but then returned to their homes. Arica's port and airport were functioning normally and Chile's Hydrographic and Oceanographic Service discounted the possibility of a tsunami. In the Tarapaca region, walls fell in some sectors and some roads were blocked by the quake, which also cut power to more than 3,000 homes in Arica. Power also was cut for a time in the Peruvian city of Tacna. A magnitude-7.1 quake struck central Chile on March 25 and in 2010, a magnitude-8.8 quake caused a tsunami that obliterated much of the downtown area of the coastal city of Constitucion.
Alaska - No injuries, damage after quake in Anchorage area. The Alaska Earthquake Information Center says the 4.6 magnitude quake occurred at 7:02 am Wednesday. It struck eight miles south of Anchorage. There were no immediate reports of damage or injuries.
VOLCANOES -
Volcano Webcams
TROPICAL STORMS -
In the Pacific -
Tropical Storm Aletta was located about 840 mi...1350 km SSW of the southern tip of Baja California.
Tropical Storm Aletta is weakening as it spins far out over the Pacific. The storm's maximum sustained winds decreased to near 40 mph (65 kph) Wednesday with gradual weakening expected.
SEVERE RAIN STORMS, FLOODING, LANDSLIDES -
Australia - Ocean temperature made Queensland floods worse. ABNORMALLY HIGH OCEAN TEMPERATURES off the coast of northern Australia contributed to the extreme rainfall that flooded three-quarters of Queensland over the summer of 2010-11, scientists report. A series of climate models found above average sea surface temperatures throughout December 2010 increased the amount of rainfall across the state by 25 per cent on average. While the study did not look at the cause of ocean warming in the region, a physical oceanographer said climate change could not be excluded as a possible driver of this extreme rainfall event.
Between December 23 and 28 many places experienced up to 400 millimetres of rain in a few days. "That [means] 100 millimetres of rain was attributable to sea surface temperatures." While the flooding occurred during ONE OF THE STRONGEST LA NINA EVENTS ON RECORD it was insufficient to produce the extreme rainfall recorded. The effect of the high sea surface temperatures coupled with the impact of a La Nina, both of which are associated with above average rainfall over eastern Australia, plus tropical cyclone Tasha, combined to create an extreme weather event.
The resulting floods stretched across 1.3 million square kilometres all the way to Brisbane, caused billions of dollars in damage and killed 35 people. Ocean temperatures off northern Australia were THE HIGHEST ON RECORD at the time of the Queensland floods. "While the La Nina event played a big role in this record ocean warmth, so too did the long-term warming trend over the past 50 years." Warmer sea surface temperatures increase the amount of moisture transferred from the ocean to the atmosphere. "If you've got the right winds they carry this moisture to land, and [because] land is hotter than the ocean during the day it will cause convection and rain."
While both simulations underestimated the amount of rain that fell in Queensland in December 2010, the model that used the higher sea surface temperatures came closest to the rainfall recorded in the region. "The model doesn't replicate the observations perfectly but it clearly shows what we saw, which was from Cairns to south-east QLD all [regions] received abnormally high precipitation." If increases in sea surface temperatures can be attributed to global warming, the probability of La Nina events producing extreme rainfall in the future would also rise.
EXTREME HEAT & DROUGHT / CLIMATE CHANGE -
Warming since 1950 'UNPRECEDENTED' in Australia - The rise in temperatures in and around Australia since 1950 has been unprecedented, a new study shows. No period during the past 1000 years matches the warming experienced in Australasia in the past 60 years. "Our study revealed that recent warming in a 1000-year context is HIGHLY UNUSUAL and cannot be explained by natural factors alone, suggesting a strong influence of human-caused climate change in the Australasian region." The researchers examined natural indicators, such as tree rings, corals and ice cores to look at temperatures over time.
The team compared the data with climate model simulations. To ensure the results were accurate, the team's reconstruction used 27 natural climate records which were calculated in 3000 different ways. The study is expected to help scientists better understand future climate variability too. The study is part of an international collaboration which aims to reconstruct the past 2000 years of climate in every part of the world.
