Katla Volcano Caldera Earthquakes 2010-Sep
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The Katla volcano located in Iceland, lies beneath the Myrdalsjokull glacier and is located next to its little sister volcano, Eyjafjallajokull, which erupted earlier this year on 14-Apr-2010. Historically, Katla has always erupted not long after Eyjafjallajokull, the longest span being 1.5 years and the shortest time span being approximately 6 months. 5 months have now gone by since the clock started ticking so lets have a look at what has happened at Katla during that time.
The image above purposely only shows earthquakes that have occurred at or within the caldera itself. I have been casually tracking this particular volcano since 17-May of this year, so this data tracks the most recent 4 months. I have identified 58 earthquakes at the caldera, and there is no doubt that I have missed a few too. Of note, the total number of Katla earthquakes that I have identified including the region outside of the glacier, but still on Katla itself, is 307 so far (again, the accurate number is probably somewhat higher).
I am focusing on the caldera because apparently many of the other earthquakes, particularly those just outside the western rim of the caldera, are being caused by seasonal glacial water runoff stresses and are not themselves indicators of potential magma movement. There are a few technical papers written on that subject, and they made logical sense having read them.
The caldera has an area of about 42 square miles (108 square kilometers) and is about 6 x 9 miles across (10 x 15 km).



I am attributing the earthquakes that are shown here on the west caldera rim as being associated with the seasonal glacial water stress factors, because when looking at the larger map, you can see that the earthquakes continue on to the west as described in the technical papers.
Stunning NASA Infrared Imagery Of Hurricane Igor Reveals A 170 Degree Temperature Differencelink

NASA satellites provide infrared images to forecasters that show temperature, and today's imagery of powerful Hurricane Igor showed the storm's perfect form and the warm ocean waters around it that are keeping it fueled. NASA's infrared data also revealed a huge difference of 170 degrees between the cold cloud tops in Hurricane Igor and the warm sea surface temperatures powering it below.
This impressive infrared image of Hurricane Igor from NASA's AIRS instrument shows a clear and large eye, and very strong convection (purple) and high, powerful thunderstorm cloud tops around his center. The image was captured from the AIRS instrument on NASA's Aqua satellite on Sept. 14 at 14:47 UTC (10:47 a.m. EDT). Note the warm ocean temperatures (dark orange) well over the 80 degree F threshold needed to maintain intensity.

Credit: NASA/JPL, Ed Olsen
When NASA's Aqua satellite passed over Igor on Sept. 14 at 14:47 UTC (10:47 a.m. EDT) the Atmospheric Infrared Sounder (AIRS) instrument captured icy cold cloud top temperatures in the strong thunderstorms that surround Igor's well-defined eye. Those cloud top temperatures were as cold or colder than -90F, indicating they were near the top of the troposphere, and very strong.
The infrared imagery also showed the warmer, open 20 nautical-mile wide eye (because it was not cloud-filled). In addition, AIRS got a reading on the sea surface temperatures around Igor, which were all warmer than the 80F threshold needed to maintain a tropical cyclone, so Igor has a good energy source for the next day or two. So, the difference between Igor's cold cloud top temperatures and the warm ocean surface waters that are powering it are greater than 170 degrees Fahrenheit!
The AIRS instrument is managed out of NASA's Jet Propulsion Laboratory in Pasadena, Calif. and NASA's Ed Olsen creates those stunning images.
At 11 a.m. EDT today, Sept. 14, Hurricane Igor was still a category 4 hurricane on the Saffir-Simpson scale with maximum sustained winds near 135 mph. It was located far from land, about 710 miles east of the Northern Leeward Islands, near 18.3 North and 52.3 West. It was moving west-northwest near 7 mph, and is forecast by NOAA's National Hurricane Center to turn toward the northwest on Wednesday. Igor's minimum central pressure is 945 millibars.
Although Igor is over 700 miles from the Northern Leeward Islands, large ocean swells will reach them today creating dangerous conditions at beaches. Large swells will reach Puerto Rico and the Virgin Islands later today and tomorrow. These dangerous surf conditions also create rip currents along the beaches.