Eyjafjallajökull is one of Europe's most famous volcanoes. In December 1821, a huge eruption stemmed from Eyjafjallajökull, creating so much ash as to block out the sun. To make matters worse, the ash contained an unnatural amount of fluoride, causing bone deformation in people and animals. In 2010, Eyjafjallajökull erupted again, this time releasing magma. The explosions came from the center crater at the top of the mountain. This caused the glaciers on the mountain to melt and rush down to the nearby rivers. The rivers flooded.