The ash cloud that is spreading from Iceland might not be visible from the ground – skies were clear in many closed airports today – since it is moving at high altitudes. Anyhow, it is extremely dangerous for planes to fly through it. The cloud not only limits visibility, but can actually damage jet engines to the point of bringing them to a halt.
In fact, the ash cloud is composed of tiny particles of rock, glass (which forms at high temperatures), and sand. A deadly mix that can effectively jam even the most advanced jet engines. The ash cloud can also be dangerous for health of individuals, but since it is moving at high altitudes, there is no significant risk for the time being, according to the U.K. Health Protection Agency.
Strong winds are spreading the ash cloud fast, mostly towards south and east; unless activity at the volcano increases substantially, the ash cloud will become less dangerous as the time passes, as it will diminish in density.
Maps
– Our map of the eruption can be found here
– Our map of countries whose air traffic is being affected by the ash cloud (Updated on April 17, 2010)
– U.K. Met Office has a map, updated as more data reaches their data centers. You can check it on their website.
– Here is also an animation from EumetSat.