Date of Award

Summer 8-1-2000

Document Type

Thesis

Degree Name

Master of Arts (MA)

Department

Geography, Geology, and Anthropology

Abstract

A number of different remote sensing techniques were used to analyze Landsat TM image data in order to study vegetation recovery patterns at three locations within the zone of devastation of Mount St. Helens (MSH). Prior to the May 18, 1980 eruption, the vegetation in the area ofMSH was characterized by mature coniferous forest disturbed only by a few clearcuts, according to analysis of Landsat MSS data. As a result of the MSH eruption, more than 600 sq. km of the area predominantly north of the volcano were severely devastated by a number of volcanic events such as phreatic explosions, a landslide, a lateral blast, dacite tephra fallout, and pyroclastic flows. Three study sites from the west, north, and east part of the blast zone have been selected and analyzed using a 1996 Landsat TM image of the area. Study areas contain ridges with slopes facing the blast and slopes facing away from it. Analysis techniques implemented included unsupervised classification, histogram analysis, and analysis of the Normalized Difference Vegetation Index (NDVI). Examination of the vegetation recovery on slopes facing and slopes facing away from the direction of the blast has shown that revegetation is more developed on the slopes facing away from the direction of the blast. It is proposed that the lateral blast has played a main role in shaping revegetation patterns within the area of devastation.

Download

Share

COinS