Today, I wanted to say a few words about the image above taken by the Terra satellite last October. Click here to embiggen and see a lot of neat details. The location of this image on the Kamchatka Peninsula is shown below. That little island on the lower-right edge of the image is Attu, the westernmost point of the Aleutian Islands coming off Alaska.
As you can see from the image I showed yesterday, these volcanoes are located near that triple junction between the North American, Pacific, and Okhotsk tectonic plates.
By the way, see those islands coming southward off Kamchatka toward Hokkaido Island in the north of Japan? Those are the Kuril Islands and just today (January 22 at 1247 UTC) they experienced a 4.7 magnitude earthquake due to the constant subduction of the Pacific Plate down the Kuril Trench at 92 mm/yr.
Let's look more closely at some of the features visible in the Terra satellite image above. The first is Klyuchevskaya volcano (also spelled Kliuchevskoi) in the lower-left part of the image.
This image was taken on October 11, 2010, at 1237 UTC (12:37 pm local time). Note that the volcano is actively erupting a plume of ash. The white on the flanks of the volcano are a mix of snow and ash and patchy white clouds are also visible. Look carefully on the left side of the crater, see the little river of red? That's a lava flow being picked up by the infrared sensors on the satellite (infrared radiation is emitted from hot objects). Here's a close-up:
Klyuchevskaya is a stratovolcano and the highest peak on Kamchatka at 4,750 m (15,584 ft). This volcano has erupted more than 50 times since it was first recorded in 1697 (and there's radiocarbon evidence of eruptions going back six thousand years). That constant eruptive activity is actually a good thing in some ways - volcanoes that are constantly erupting like this are generally well-behaved and not too dangerous (although the ash plumes rise to 26,000 feet or more and can disrupt air traffic). It's also a great place for volcanologists to study volcanic processes - the Kamchatka Volcanological Station was established at its base in 1935.
Klyuchevskaya from Global Volcanism Program
Another volcano seen in the image is Bezymianny (lower-left), which is just to the south of Klyuchevskaya volcano. Note the shadow of the volcano indicating the Sun is to the south (expected in Kamchatka in October) and the plume rising from the crater. This is just a steam plume (meltwater seeping into fractures and heating into steam due to the hot rock at depth) as no explosive activity was recorded at this time.
Bezymianny was once though to be extinct, until it violently erupted in 1955-1956 and blew out the east-southeast side of the volcano leaving behind a horseshoe-shaped crater (very similar to the way Mt St Helens erupted in Washington State back in 1980). A large lava dome now exists in the crater with intermittent explosive activing and pyroclastic flows.
The third major volcano in the Terra satellite image is Shiveluch which is located in the northeastern part of the Terra satellite image. Shiveluch is one of the most active stratovolcanoes in Kamchatka and was erupting a plume of ash when this image was taken (crater is circled in red).
Shiveluch from Global Volcanism Program
Scrolling around the large Terra satellite image, you can see a lot of other volcanic features (in some places, it almost looks like the area was struck by a storm of meteorites). There's also a curious horsehoe-shaped structure near the center of the image.
It's an old volcanic caldera, breached to the southeast. Extinct now, but once the site of a powerful explosive eruption that would have killed anything living within miles in that direction.