Scientists generated computer models of how the complicated structure of the Earth's mantle layer under the western United States evolved over the past 40 million years. The researchers suggest that about 17 million years ago, a giant chunk of rock known as the Farallon slab that was diving underneath the western United States began ripping apart. This led to massive outpourings of magma, the pattern and timing of which appear consistent with the Steens–Columbia River flood basalts. "When the slab is first opened, there's a little tear, but because of the high pressure underneath, the material is able to force its way through the hole. It's like in the movies when a window breaks in an airplane that is at high altitude — since the cabin is at higher pressure, everything gets sucked out the window."
Intriguingly, the supervolcano at Yellowstone seems to be due to a mantle plume under the area, but the researchers do not think it was involved with the Steens–Columbia River flood basalts. "There are 40 to 50 active mantle plumes in the Earth right now, so just because one is close doesn't mean that it was behind these flood basalts." "Only with a break of this scale inside the down-going slab can we reach the present-day geometry of mantle we see in the area. Geochemical evidence from the Columbia River lavas can also be explained by our model."
Future research can also investigate the effects of slabs of rock diving underneath other tectonic plates. These new findings shed light on a way — in addition to mantle plumes — that volcanoes can emerge within tectonic plates. Volcanoes are most often seen at the boundaries of tectonic plates. "There are subducted tectonic plates, or slabs, underneath South America we'd want to understand better, and slabs underneath south Asia where there was a collision between India and Eurasia, and slabs underneath the Pacific Northwest, such as the Aleutians and central Alaska."
to find the best in others, to give one's self...
this is to have succeeded.**
Ralph Waldo Emerson
LARGEST QUAKES -
This morning -
5.1 MAURITIUS - REUNION REGION
Yesterday -
2/15/12 -
5.1 NICOBAR ISLANDS, INDIA REGION
5.8 EASTERN NEW GUINEA REG., P.N.G.
5.0 NEAR EAST COAST OF HONSHU, JAPAN
5.9 OFF COAST OF OREGON
5.3 FIJI REGION
VOLCANOES -
Canary Islands - Underwater Volcano Still Erupting. The underwater eruption off the Canary Island of El Hierro has been going on for more than four months, with volcanologists watching the spectacle to see if it might generate a new island. El Hierro, the youngest of the Canary Islands, lies 290 miles (460 kilometers) west of the coast of Morocco and Western Sahara. El Hierro last erupted in 1793 and the area has the greatest concentration of young vents in the Canary Islands. The new eruption is occuring just off the coast, near the fishing village of La Restinga.
NASA's Earth Observing-1 satellite captured a picture of the ongoing eruption on Feb. 10. The bright aquamarine waters visible in the images indicated a high concentration of volcanic material, including steaming lava fragments, bits of rock and heated gas. Immediately above the vent was a patch of brown water that can resemble a turbulent hot tub when the eruption is strongest. Measurements of the sea floor indicate that the summit of the volcanic cone growing over the vent is now only 390 feet (120 meters) beneath the ocean surface - 30 feet (10 m) higher than it was in mid-January. The height of the erupting cone is about 690 feet (210 m) from the former ocean bottom, with a total volume over 512 million cubic feet (145 million cubic meters) of new material. Images of the new cone emerged in November 2011. (photo)
Oregon - Scientists discover reason Mt. Hood tends to be quiet. For a half-million years, Mount Hood has towered over the landscape, but unlike some of its cousins in Oregon’s Cascade Mountains and many other volcanoes around the Pacific “Rim of Fire,” it doesn’t have a history of large, explosive eruptions. Now a team of scientists has found out why.
Mixing of magma deep beneath Mount Hood appears to have prevented it from blowing its top over the millennia. Studies of the rocks around Mount Hood show that the volcano has never experienced a violent eruption despite having similar chemical magma composition and gas contents as other volcanoes that have.
The reason is that eruptions at Mount Hood appear to be preceded by episodes of intense mixing between magmas of different temperatures. Hot magma rises from deep below Mount Hood and mixes with the cooler magma that underlies the volcano. Heat from the deeper, hotter magma increases the temperature and lowers the viscosity of the magma that eventually erupts. Instead of exploding, a la Mount St. Helens, magma at Mount Hood oozes out the top of the volcano and piles up to form a lava dome.
What happens instead of an explosive eruption is more of a hiccup. “Instead of an explosion, it would be more like squeezing a tube of toothpaste. Lava piles up to form a dome; the dome eventually collapses under its own weight and forms a hot landslide that travels down the side of the volcano. In contrast, during a Plinian event such as the kind seen at other volcanoes, ash and rock are blown high into the air and distributed all over.” Although Mount Hood lacks an explosive history, it doesn’t mean the peak is completely docile. Collapses of the lava dome at Crater Rock about 1,500 years ago, and again 220 years ago, sent scalding landslides of hot lava blocks down the south side of the volcano. “These types of events have dominated the eruptive activity at Mount Hood for the past 30,000 years. The other danger is from lahars, which are major mudflows that stream down the side of the mountain at some 50 miles-an-hour, with the consistency of cement. They result when heat from the magma melts snow and mixes it with the volcanic ash and rock.
Lahars probably accompany most eruptions of the volcano, and can even occur between eruptions after heavy rains or rapid snowmelt. And they can go quite a ways — all the way to the Columbia River, for instance.” Few other volcanoes around the world act quite like Mount Hood. It is a poster child for low-explosivity eruptions.
TROPICAL STORMS -
In the Indian Ocean -
-Tropical cyclone 12s (Giovanna) was located approximately 450 nm east of Maputo, Mozambiqone is hammering Tonga's main island of Tongatapu with major flooding occurring and phone and electricity lines down. Cyclone Jasmine was born on February 4 over the Queensland city of Cairns.
Philippines - Potential cyclone nears Davao. Floods and landslides threaten parts of Bicol, Visayas and Mindanao as a potential cyclone — a low-pressure area — moved close to Davao City in Mindanao before noon Thursday. If the low pressure area consolidates and strengthens into a tropical cyclone, it would be named Ambo, the first storm to enter the Philippine area of responsibility in 2012.
SEVERE RAIN STORMS, FLOODING, LANDSLIDES -
Australia - Flood victims to be isolated until April. More than 8000 people remain isolated two weeks after a deluge struck communities in northern NSW. Most of these flood victims will remain cut off for up to another month while a smaller number of them might have to wait until April to see dry land. Flooded communities in the northwest of the state are getting about 50 tonnes of relief goods delivered daily. "We distribute relief goods to each individual house via helicopter."
Rver levels were dropping slightly or holding steady. But the floodwaters are slowly moving further west and are expected to swamp towns such as Brewarrina, Bourke, Tilpa and Louth. Several highways and local roads will remain closed until the floodwaters clear. "Thankfully, no major injuries have been reported." The NSW government this week extended natural disaster declarations to Brewarrina and Walgett, taking the total number of zones to 23.
HEALTH THREATS -
Tainted Jimmy John's sprouts linked to illnesses in 5 states.
