At 2300 on 13 April, a seismic swarm was detected below the central part of Eyjafjöll, W of the previous eruption fissures. About an hour later, the onset of seismic tremor heralded an eruption from a new vent
on the S rim of the central caldera, capped by Eyjafjallajökull glacier. The eruption was visually confirmed early in the morning on 14 April; an eruption plume rose at least 8 km above the glacier.
Meltwater flowed to the N and S. News outlets reported that a circular ice-free area about 200 m in diameter was seen near the summit. Scientists conducting an overflight saw a new 2-km-long, N-S-trending fissure, and ashfall to the E. About 700 people were ordered to evacuate the area, and certain flights were banned from flying N and E of the eruption area. Flooding increased throughout the day, causing road closures and some structural damage.
Geologic Summary. Eyjafjöll (also known as Eyjafjallajökull) is located immediately west of Katla volcano. Eyjafjöll consists of an E-W-trending, elongated ice-covered basaltic-andesite stratovolcano
with a 2.5-km-wide summit caldera. Fissure-fed lava
flows occur on both the eastern and western flanks of the volcano, but are more prominent on the western side. Although the 1666-m-high volcano has erupted during historical
time, it has been less active than other volcanoes of Iceland's eastern volcanic zone, and relatively few Holocene
lava flows are known. The sole historical eruption of Eyjafjöll, prior to an eruption in 2010, produced intermediate-to-silicic tephra
from the central caldera
during December 1821 to January 1823.