سیل در تایلند Flooding in Thailand

The Chao Phraya River forms at the confluence of smaller rivers in central Thailand, and flows southward to the Gulf of Thailand. En route to the sea, the river passes through Ayutthaya. Historic City of Ayutthaya. First established in the fourteenth century, Ayutthaya lies north of Thailand’s capital city of Bangkok, and the floods plaguing Thailand in October 2011 did not spare this historic city.

The Advanced Land Imager (ALI) on NASA’s Earth Observing-1 (EO-1) satellite acquired these natural-color images of Ayutthaya on October 23, 2011 (top), and July 11, 2011 (bottom). In both images, the Chao Phraya River curves through the southwestern part of the city (image lower left). In October, however, the river has overflowed onto nearby floodplains, especially southwest of the river and west of Route 356. Fields, roads, and buildings have all been submerged by sediment-clogged flood water.

Thailand’s monsoon generally lasts from mid-May to September. Because these images show the region at different times of year, some of the differences in water and vegetation could result from normal seasonal variations. However, the large expanse of flood water in October 2011 is unusual even in a monsoon season.

Flooding forced the closure of manufacturing plants in Ayutthaya, according to news reports. The city is a United Nations Educational, Scientific and Cultural Organization (UNESCO) World Heritage site. On October 12, UNESCO Bangkok announced a planned assessment of flood damage to Ayutthaya, requested by the government of Thailand.

1.   References

2.   CIA World Factbook. (2011, October 18). Thailand. Accessed October 26, 2011.

3.   MacManus, C. (2011, October 24). Thai floods drown Sony Alpha cameras. CNET News. Accessed October 26, 2011.

4.   The Mainichi Daily News. (2011, October 25). Japan gears up for rescue of companies in flood-hit Thailand. Accessed October 26, 2011.

5.   UNESCO Bangkok. (2011, October 13). UNESCO to assess flood-affected Ayutthaya World Heritage site. Accessed October 26, 2011.

6.   World Heritage. (2011). Historic City of Ayutthaya. UNESCO. Accessed October 26, 2011.

فوران آتشفشا ن زیر دریا El Hierro Submarine Eruption

Off the coast of El Hierro, in the southwest reaches of the Canary Islands, Earth has been spewing gas and rock into the ocean. The island off the Atlantic coast of North Africa—built mostly from a shield volcano—has been rocked by thousands of tremors and earthquakes since July 2011, and an underwater volcanic eruption started in mid-October. The eruption is the first in the island chain in nearly 40 years.

On October 23, 2011, the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Terra satellite captured this natural-color view of El Hierro and the North Atlantic Ocean surrounding it. A milky green plume in the water stretches 25-30 kilometers at its widest and perhaps 100 kilometers long, from a large mass near the coast to thin tendrils as it spread outs to the southwest. The plume is likely a mix of volcanic gases and a blend of crushed pumice and seafloor rock.

Tremors were reported for the past several months from seismic stations on El Hierro, particularly in the northwest of the island. Then on October 12, 2011, the strength of the tremors significantly decreased while foaming, rock-strewn plumes appeared in the sea to the south of the island. The underwater plume of volcanic debris has persisted for nearly two weeks and has been mixed and dispersed by ocean surface currents. The eruption is occurring in water that is tens to a few hundred meters deep.

Geologist and blogger Erik Klemetti offered this analysis: “It looks like the main fissure might be 2-3 kilometers in length and is close to on strike with the rift axis for the main El Hierro edifice. Ramon Ortiz, coordinator of a government scientific team, said that if/when the eruption reaches shallower water, we should expect to see the surface water start to steam, followed by explosions of steam and magma and finally the emergence of an island.”

For local seismic information from El Hierro (in Spanish), visit the Instituto Geographico Nacionale.

1.   References

2.   The Daily Mail (2011, September 29) Earthquake swarm on Canary Island of El Hierro sparks fears of volcanic eruption.Accessed October 25, 2011.

3.   Global Volcanism Program (2011, October 18) Smithsonian/USGS Weekly Volcanic Activity Report: Hierro. Accessed October 25, 2011.

4.   Klemetti, Erik (2011, October 21) Eruptions Blog: Vulcan’s View: Eruption News and Volcanoes From Space. Accessed October 25, 2011.

جریان گدازه و خاکستر آتشفشا ن در آتشفشان " نابرو " واقع در بین " اریتره " و " اتیوپی " Ash and Lava Flows at Nabro Volcano

Satellite imagery suggests that the eruption of Nabro Volcano, which began in June 2011, continues. The volcano is located on the edge of the Danakil Desert, a remote and sparsely populated area on the border between Eritrea and Ethiopia, and few eyewitness accounts of the eruption are available. Orbiting instruments such as the Advanced Land Imager (ALI) aboard Earth Observing-1 (EO-1), which acquired these images, may be the only reliable way to monitor Nabro.

The images show the volcano in false-color (top) and natural-color (lower) on September 28, 2011. Heat from vents in Nabro’s central crater is visible as a red glow in the false-color image. Another hotspot about 1,300 meters (4,600 feet) south of the vents reveals an active lava flow. A pale halo surrounding the vents indicates the presence of a tenuous volcanic plume. South of Nabro’s crater, the dark, nearly black areas are coated with ash so thick it completely covers the sparse vegetation. On either side of this region is a thinner layer of ash with some bright green vegetation (exaggerated in false-color) poking through.

In the natural-color image, the arid landscape is light brown where it is not covered by ash. The ash is black, while a fresh lava flow, spewed out in the last two weeks of June, is dark brown. More fresh lava flows surround the active vents. On either side of Nabro’s caldera, ephemeral streams have washed away the ash, leaving light-colored channels behind—a first sign of the erosion that will reshape, and eventually remove, what the eruption built.