Mt. St. Helens from Landsat: 1973 to 1992

These images show Mt. St. Helens almost a decade before the May 18, 1980, eruption, approximately three years after the eruption, then a pair of images over the following decade, as the landscape recovered. Notice in particular the area northwest of the mountain, past the Toutle River, where forest coverage has recovered somewhat in the past ten years.

North is up in all these images. The 1973 Landsat 1 image used MSS bands 7, 5, and 4 (called MSS 4, 2, and 1 on the later Landsat satellites) displayed as red, green, and blue respectively. The other images mapped TM bands 4, 3, and 2 to red, green, and blue. This color combination is often referred to as 'false color infrared' since it has a similar appearance and tone to color infrared photography. Reds represent vegetation (which is a strong reflector of near infrared light), grays are exposed land, and light blues show snow on the peaks of Mt. St. Helens and neighboring Mt. Adams. The Columbia River snakes into view in the lower left corner, just north of Portland, Oregon.

See http://svs.gsfc.nasa.gov/stories/Landsat/index.html