Startling new images from the depths of the Pacific Ocean reveal one of Earth's most violent processes: the destruction of massive underwater mountains. The pictures were created by sonar in waters up to 6km (4mi) deep. They expose how tectonic action is dragging giant volcanoes into a chasm in the seabed. The volcanoes are strung across several thousand kilometres of ocean floor and are moving westward on the Pacific tectonic plate at up to 6cm per year. The extraordinary scene was captured along the Tonga Trench during a research expedition last summer. The trench is a highly active fault line running north from New Zealand towards Tonga and Samoa.
Where the Pacific plate collides with the Indo-Australian plate, it is forced downwards into the trench, a subduction zone, and the volcanoes are carried with it. The trench, reaching a depth of 10.9km, forms the second deepest stretch of seabed anywhere in the world - easily large enough to hold Mount Everest.
One image shows the volcano nearest the edge of the abyss - the next to be destroyed - already starting to collapse. With frequent earthquakes, the region is vulnerable to tsunamis and one aim of the research is to understand whether the destruction of the volcanoes adds to the risk. One theory is that the volcanoes add friction to the movement of the two plates which leads to a greater build-up of tension and consequently to a more explosive quake. Another is that by shearing into blocks as they collapse, the volcanoes provide a kind of buffer easing the subduction process.
Earthquakes are less frequent at the precise point where the volcanoes enter the trench. "When you see the size of these features you'd think they'd cause massive earthquakes and disruption - and that was our starting hypothesis. But we found that the volcanoes were highly fractured before they entered the trench - which is very important for what happens after they enter the system." Analysis so far has not determined the precise impact of this process. "Are they added to the Australian plate or are they carried down in fragments into the deep earth mantle?"
Samuel Beckett
LARGEST QUAKES -
This morning -
5.5 TONGA
Yesterday -
12/6/11 -
5.0 TONGA
5.0 TONGA
INDIA - Sikkim drastically de-stabilised by quake. A recent report by the State department of Mines and Geology has warned the Sikkim Government that the overall soil and rock stability of the entire State has been drastically destabilised by the 6.9 Richter scale earthquake that hit the State on September 18. This would trigger off multiple landslides in the coming monsoon season as already post-quake Sikkim has had more than 150 slides induced by the earthquake. 12 need urgent remedial action while another 32 need long term intervention.
The report has also warned of Glacial Lake Outburst Floods in the higher reaches and called for close monitoring of these lakes. The impact of the quake was more on the crystalline rocks, mainly on its quartzites and variants with adverse slopes and on landmasses adjoining steep slopes and waterways. It suggested that in the short term, soil compaction on fissures on landmasses to minimise seepage and use of local technologies to retain unstable boulders, apart from identification of high risk zones and preparedness for disaster mitigation and planning in advance. It also suggested use of remote sensing and GPS tracking aerial photographs to tackle disasters in remote areas. Banks and international agencies have been approached by the State Government for rebuilding efforts following the large-scale damages to infrastructure during the earthquake of September 18.
VOLCANOES -
TRINIDAD - Piparo volcano goes silent. Although the rumblings and gas spurts from the Piparo mud volcano are slowly subsiding, the Office of Disaster Preparedness is maintaining a safety alert. Over the past few days hundreds of people have been flocking to the area to look at the volcano which has been dormant for 14 years since a huge eruption on February 22, 1997. Following loud eruptions and heightened activity on Friday and Saturday, the volcano has become quiet. A resident said, “We are relieved because the last time it erupted, we had to run for our lives. We already packed a bag with all the important documents. If we feel the place shaking, we will grab the bag and run."
“The volcano is very silent and it is not talking to us at all. We are continuing to monitor it. We haven’t called off the alert. The experts have said we should watch it until the end of tomorrow to see if it settles down." It was seepage of surface water into the heated areas, not seismic activity, that triggered the gas spurts and rumblings.
TSUNAMI / FREAK WAVES / ABNORMAL TIDES -
Two Waves Formed Japan's Destructive Tsunami - The tsunami that devastated coastal areas of Japan in March was actually the result of two waves coming together to form a "merging tsunami". NASA and European radar satellites captured images of at least two wave fronts forming in the ocean after the 9.0 earthquake struck the region in March. They came together in a single wave that, because of its joined strength, was able to travel long distances without losing steam over ocean ridges and mountain chains that continuously pushed the waves together.
This observation was a rare glimpse of how tsunamis can cross miles of ocean to cause massive destruction in some places, while leaving others unharmed, researchers said. They hope to use the information to better predict tsunami activity and develop better forecasting and warning systems. "It was a one in 10 million chance that we were able to observe this double wave with satellites." Researchers had believed for years in the phenomenon of two waves forming to cause a tsunami of this kind, but it had never before been proven.
Current predictions for where a tsunami will hit are based on topography maps of the sea floor, which has ridges and mountains that push tsunamis in various directions. For this reason, its destruction once it hits land can appear random. However, by verifying the wave formation observed by the satellites through computer simulations and using other data, scientists may be able to create maps that take into account a vaster region of the seafloor to make better predictions in the future.
TROPICAL STORMS -
In the Indian Ocean -
-Tropical cyclone 01s (Alenga) was located approximately 535 nm west of the Cocos Islands.
-Tropical cyclone 02s was located approximately 760 nm east- northeast of La Reunion.
EXTREME HEAT & DROUGHT / WILDFIRES / CLIMATE CHANGE -
Glaciers in the French Alps have lost a quarter of their area in the past 40 years, according to new research. In the late 1960s/early 1970s, the ice fields slipping down Mont Blanc and the surrounding mountains of the European range covered some 375 sq km. By the late 2000s, this area had fallen to about 275 sq km. It mirrors some findings of retreat occurring in other sectors of the Alps which sit across the borders of several nations, but predominantly Switzerland, Austria, Slovenia, Germany, France, and Italy.
A great deal of effort is now going into monitoring the status of Alpine glaciers The only existing glacial inventory from the French Alps was published four decades ago within the context of the World Glacier Inventory. It found the overall area of ice to be about 375 sq km. By 1985-86, in spite of a short advancing period in the late 70s/early 80s, glacial coverage had decreased to a value close to 340 sq km, the new survey shows.
Since then, the withdrawal has accelerated. The retreat is not uniform across the French Alps, however. The greatest losses have been seen in the southern sectors. In the Belledonne Massif, for example, glaciers have almost completely disappeared; and in the Ecrins Massif, glacial retreat is more than three times stronger than in the Mont Blanc Massif. "The glacier retreat is less important in the northern Alps than in the southern Alps. We think this is because of the lower elevation of the mountains in the south, but also because of climatic conditions which are different. There is more precipitation in the north and there is also more cloud."
The northern region includes the biggest French glacier of all - La Mer de Glace, which falls over a 1,000m in altitude down Mont Blanc itself. Its area today is just over 30 sq km, a shade smaller than the 31.5 sq km in the late 1960s/early 1970s. Efforts to assess and monitor glacier health are going on across the Alpine region. Three years ago, Swiss researchers reported that glaciers on their part of the European range were also losing mass at an accelerating rate.
