Mount Rainier eruptions may be taken into consideration because mount Rainier is one of the most dangerous volcanoes in the world, and it is on the Decade Volcano list.The most recent recorded volcanic eruption was between 1820 and 1854, but many eyewitnesses reported eruptive activity in 1858, 1870, 1879, 1882 and 1894 as well.
Although Mount Rainier volcano is an active volcano, as of 2010 there was no evidence of an imminent eruption. However, an eruption could be devastating for all areas surrounding the volcano Mount Rainier is currently listed as a Decade Volcano, or one of the 16 volcanoes with the greatest likelihood of causing great loss of life and property if eruptive activity resumes. If Mt. Rainier were to erupt as powerfully as Mount St. Helens did in its May 18, 1980 eruption, the effect would be cumulatively greater, because of the far more massive amounts of glacial ice locked on the volcano compared to Mount St. Helens and the more heavily populated areas surrounding Rainier Lahars from Rainier pose the most risk to life and property, as many communities lie atop older lahar deposits. Not only is there much ice atop the volcano, the volcano is also slowly being weakened by hydrothermal activity. According to Geoff Clayton, a geologist with a Washington State Geology firm, RH2 Engineering, Mount Rainier eruption would destroy Enumclaw, Orting, Kent, Auburn, and most or all of Renton. Such a mudflow might also reach down the Duwamish estuary and destroy parts of downtown Seattle, and cause tsunamis in Puget Sound and Lake Washington. According to USGS, about 150,000 people live on top of old lahar deposits of Rainier. Rainier is also capable of producing pyroclastic flows as well as lava.
Scientist K. Scott said: “A home built in any of the probabilistically defined inundation areas on the new maps is more likely to be damaged or destroyed by a lahar than by fire…For example, a home built in an area that would be inundated every 100 years, on the average, is 27 times more likely to be damaged or destroyed by a flow than by fire. People know the danger of fire, so they buy fire insurance and they have smoke alarms, but most people are not aware of the risks of lahars, and few have applicable flood insurance.”
The volcanic risk is somewhat mitigated by lahar warning sirens and escape route signs in Pierce County. However, although more populous King County is also in the Lahar area, there are currently no zoning restrictions in King County due to volcanic hazard. More recently (since 2001) funding from the federal government for lahar protection in the area has dried up, leading local authorities in at-risk cities like Orting to fear a disaster similar to the Armero tragedy. [Article Source: wikipedia.org]
So, how do we know when to run for the hills? No one seems to be able to offer an estimation of when. Geologists can only look at history and predict what could happen. However, the warning signs that would precede a lethal Mount Rainier eruption would give the residents of nearby towns plenty of time to pack there bags and evacuate.