Grimsvotn is Iceland's most active volcano, but before it erupted on May 21, sending a plume of ash 12 miles into the sky, it hadn't exploded so forcefully in more than 100 years. Since 1902, according to NASA, which captured this photograph using the Moderate Resolution Imaging Spectroradiometer (MODIS) attached to the Terra satellite. It "shows the towering ash plume at 1:00 p.m. local time," NASA reported. "Lingering snow is visible beneath the clouds to the northeast (upper left). Brown ash covers a portion of the Vatnajokull Glacier near the Atlantic coast (lower right)."
That ash covered most of Iceland, leaving some areas of the country pitch black by the middle of the day on the 22nd, and shut down Kaflavik Airport, which is Iceland's largest. "This eruption is not expected to disrupt air travel as much as that of Eyjafjallajokull in 2010 because the Grimsvotn ash particles are larger and settling out of the atmosphere more quickly."
In fact, were Grimsvotn not buried underneath a massive glacier, its eruption probably wouldn't have been nearly as devastating. The basaltic lava found in Grimsvotn is similar to that in most Hawaiian volcanoes and leads to non-explosive eruptions. The interaction between the lava and the melting ice of the glacier, however, can, as it did this time, create a relatively short explosive eruption; the eruption settles down after the initial stages, when most of the glacial ice has melted.
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