LIDAR animation of Mt. St. Helens crater floor

http://vulcan.wr.usgs.gov/Volcanoes/MSH/Eruption04/Monitoring/eruption_monitoring_oct-nov_2004.html
This animated series of LIDAR images shows changes in the crater floor of Mt. St. Helens during the 2004 eruption. LIDAR uses laser (i.e. light) to determine distances, compositing into an image, as opposed to doppler or sonar, which use microwave and sound, respectively.