Wednesday, March 17, 2010
Cyclone Twins: Tropical Cyclones Tomas and Ului
Two fierce tropical cyclones raged over the South Pacific Ocean in mid-March 2010, the U.S. Navy’s Joint Typhoon Warning Center (JTWC) reported. Over the Solomon Islands, Tropical Cyclone Ului had maximum sustained winds of 130 knots (240 kilometers per hour, 150 miles per hour) and gusts up to 160 knots (300 km/hr, 180 mph). Over Fiji, Tropical Cyclone Tomas had maximum sustained winds of 115 knots (215 km/hr, 132 mph) and gusts up to 140 knots (260 km/hr, 160 mph).
The Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Terra and Aqua satellites captured both storms in multiple passes over the South Pacific on March 15, 2010, local time. The majority of the image is from the morning of March 15 (late March 14, UTC time) as seen by MODIS on the Terra satellite, with the right portion of the image having been acquired earliest. The wedge-shaped area right of center is from Aqua MODIS, and it was taken in the early afternoon of March 15 (local time).
Although it packs less powerful winds, according to the JTWC, Tomas stretches across a larger area. It was moving over the northern Fiji islands when Terra MODIS captured the right portion of the image. According to early reports, Tomas forced more than 5,000 people from their homes while the islands sustained damage to crops and buildings.
The JTWC reported that Tomas had traveled slowly toward the south and was passing over an area of high sea surface temperatures. (Warm seas provide energy for cyclones.) This storm was expected to intensify before transitioning to an extratropical storm.
Ului is more compact and more powerful. A few hours before this image was taken, the storm had been an extremely dangerous Category 5 cyclone with sustained winds of 140 knots (260 km/hr, 160 mph). Ului degraded slightly before dealing the southern Solomon Islands a glancing blow. Initial news reports say that homes were damaged on the islands, but no one was injured.
Like Tomas, Ului had been moving westward over an area of high sea surface temperatures. This storm was expected to continue moving westward before turning south and eventually weakening.
Pakistan Mud Volcanoes
Along the coast of Pakistan, the tectonic plate underlying the Arabian Sea is diving beneath the Eurasian continent. This process—subduction—typically creates volcanoes, but the volcanoes that rise from this arid landscape are not the typical kind. Instead of lava, ash, and sulfur dioxide, these volcanoes spew mud and methane. On rare occasions, the gas plumes spontaneously ignite, shooting flames high into the sky.
This natural-color image shows the most dramatic group of mud volcanoes in the area, known as the Changradup Complex. The tallest volcano, Changradup I, is about 100 meters (330 feet) high, and it has a 15-meter- (49-foot-) diameter mud lake in its crater that periodically overflows. Some of these overflows have darkened the northwestern flanks. A second crater emerges from the southern flanks of Changradup, but it is not currently active.
The 45-meter (150-foot) Chandragup II lies northeast of the taller cone, and its crater is filled by a mud lake with a figure-8 shape, probably the result of twin volcanoes whose craters collapsed into each other over time. To the northwest of Changradup I, the eroded rim of an extinct mud volcano is visible; its eastern rim is more noticeable than its western rim.
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