7 August 2008
The online site Oregon Environmental News has today carried a rather nice article on a new, large, rock and snow avalanche on Mount Adams (Fig. 1) in the Cascade Range in Washington State. Mount Adams is a stratovolcano that has a long history of such events. Many readers will be aware for example of the 31st August 1997 event, which had a volume of about 5 million cubic metres, and is well documented by the USGS.
This event was first picked up at about 14:50 UT on 1st August at the seismometers at the Cascades Volcanic Observatory, who have kindly put the seismic record online (Fig. 2).
The seismologists quickly recognised that this event was not volcanic in origin, but was in fact associated with a mass movement. As a result, they contacted a local photographer, who went up there and confirmed that a rock and snow avalanches about 2 miles (3 km) has occurred. H.C Tupper has been able to collect a photograph of the event (Fig. 3).