Hazards Associated with an Eruption

Based on the type of volcano (stratovolcano) and the amount of time since its last eruption, Mount Rainier stands a good chance of erupting in the near future. It is important to note that presently there is no dramatic increase in activity to indicate an eruption is imminent. There is geothermal activity such as hot spots and steam explosions, but it's not known if they have increased from past activity (Harris and Kiver, 1985:132). The greater understanding scientists are gaining about volcanoes has enabled them to warn us of the possibility of eruption in the foreseeable future.

Cascade eruptions have occurred an average of 1-2 per century over the last 4,000 years (USGS Open-File 94-585). Geological evidence shows that the last eruption of Mount Rainier was as recent as the 1840s and that larger volcanic eruptions took place 1,000 to 2,300 years ago (Sisson, 1995).

As with other stratovolcanoes, Mount Rainier will erupt violently, releasing long built-up pressure. The major types of hazards that will accompany an eruption at Mount Rainier are: tephra fall, lava flow, and pyroclastic flow.