How does the eruption of Mount Rainier effect the environment?

Answer 1

The last officially recorded (minor) eruption of Mount Rainier was in 1854 although there are unofficial eyewitness acounts of activity in 1858, 1870, 1879, 1882 and 1894 as well. Rainier is considered one of the most dangerous volcanoes in the world. It is heavily glaciated and when it blows it will likely produce massive debris avalanches, and has enormous lahars (volcanic mudflows) due to the large amount of glacial ice present. Lahars from previous mudflows have reached all the way to Puget Sound. Around 5,000 years ago, a large chunk of the volcano slid away and that debris avalanche helped to produce the massive Osceola Mudflow, which went all the way to the site of present-day Tacoma and south Seattle. Clearly the greatest environmental effect would be the lahar flows which would wash away towns and cities in their path and bury the area in avalanche debris and mud. It is doubtful the towns and cities would be rebuilt any time soon. Previous debris flows filled river valleys to a depth of hundreds of feet near the volcano, and have buried the land surface under many feet of mud and rock sixty miles downstream. A major lahar flow would significantly alter the course of rivers in the area and dump significant amounts of material - much of it toxic to aquatic life - into the ocean.

A second source of environmental impact from an eruption of Mount Rainier would be ash and gases injected into the atmosphere during an eruption. Enormous volumes of ash and the gas SO2, injected into the atmosphere

by large eruptions, can cause global cooling, shortening growing seasons and reducing crop yields. Ironically, eruptions of Mount Rainier usually produce much less volcanic ash than do eruptions at the smallerMount St. Helens. Nevertheless ash from a full eruption would likely spread ash across a wide area choking animals near the volcano. The released gases and ash would cause a temporary cooling of the earth, primarily in the northern hemisphere. Deposited ash would probably kill off plant life where it formed thick layers, but add a little bit of useful nutrients to soils where the deposits were light.