The initial eruption of Grímsvötn on May 21, 2011, reached 20 kilometers (12 miles) high, more than twice the height of last year's eruption of Eyjafjallajökull, which only reached 8 kilometers (5 miles). The material spewed from Grímsvötn however is coarser and heavier and not expected to remain aloft for as long or as far. This image shows the plume as the volcano continued to erupt on May 23.

The eruption of the Grímsvötn volcano sent thousands of tonnes of volcanic ash into the sky on May 23, 2011, above Iceland. During the peak of the eruption, Grímsvötn produced 1,000 times as many lightning strikes per hour as Eyjafjallajökull had a year earlier.

This image shows the plume as Grímsvötn continued to erupt on May 23.

Mammatus clouds are seen above the plume as the eruption of Grímsvötn continued on May 23, sending thousands of tonnes of volcanic ash into the sky above Iceland.

The MODIS instrument on NASA's Terra satellite captured this natural-color image of the Grímsvötn volcano eruption in Iceland on May 22, 2011, at 05:15 UTC (5:00 a.m. local time). NASA's Earth Observatory reports that "above Grímsvötn’s summit, volcanic ash forms a circular brown plume that towers above the surrounding clouds. In the southeast, ash has colored the snow surface dark brown. Ash from the volcano reduced visibility to about 50 meters (160 feet) in some places."

The MODIS instrument on NASA's Terra satellite captured this natural-color image of the Grímsvötn volcano eruption in Iceland on May 22, 2011, at 13:00 UTC (1:00 p.m. local time).

Contrails over Buckingham Palace during the meeting of President Obama with the Royal family on Tuesday provided visible signs that the ash from Iceland's Grímsvötn volcano is proving far less disruptive than last year's eruption of Eyjafjallajökull. Even so, hundreds of flights have been canceled leaving thousands of passengers in airline limbo. To avoid the oncoming plume, Monday night President Obama left Ireland aboard Air Force One for London earlier than planned. He is scheduled to visit Poland and attend the G8 meeting in Deauville, France, before returning to the United States. On Sunday he will meet with residents of the tornado-struck city of Joplin, Mo.