A volcano (Bogoslof) in Alaska which has been erupting periodically since December has now released its biggest ash cloud to date. The eruption lasted for 3 hours and spewed ash up to an altitude of 35,000 feet. Ash clouds which are higher than 20,000 pose a threat to aircraft as the ash can damage the engines. This is the 36th eruption in 3 months. The Volcano is 850 miles from Anchorage and is during a high state of alert as more eruptions are possible at any time.