MOUNT RAINIER is the highest mountain of the Cascade Range. It is a large STRATO VOLCANO and is located 87 km southeast of Seattle.
Mount Rainier was first known as TALOL or TACOMA or TAHOMA by the Native Americans. One hypothesis of the word origin is that TACOMA means “larger than Mount Baker”. TA (larger) + KOMA (Mount Baker). In 1890, the US Board of Geographic Names declared that the mountain would be known as RAINIER.
With 26 major glaciers and 93sq.km of permanent snowfields, Mount Rainier is the most heavily glaciated peak. The summit is topped by two volcanic craters, each more than 1,00oft in diameter, with the larger east crater overlapping the west crater. Geo-thermal heat from the volcano keeps areas of both craters with nearly 3.2km of passages. A small “crater lake”, about 130 x 30ft in size and 16ft deep, the highest in North America with a surface elevation of 14,203ft, occupies the lowest portion of the west crater below more than 100ft of ice and is accessible only via the caves.
The broad top of Mount Rainier contains three named summits. The highest is called the COLUMBIA CREST, the 2nd summit is POINT SUCCESS and it has a topographic prominence of about 138ft, so it is not considered a separate peak. The lowest of the 3 summits is LIBERTY CAP, which overlooks Liberty Bridge, the Sunset Amphitheatre and the dramatic Willis Wall. High on the eastern flank of Mount Rainier is a peak known as LITTLE TAHOMA PEAK, an eroded remnant of the earlier, much higher, Mount Rainier.
Mount Rainier is a STRATO VOLCANO and its early volcanic deposits are estimated at more than 840,000 years old. The early deposits formed a “proto-Rainier” or an “ancestral” cone. The volcano is highly eroded with glaciers and appears to be made mostly of ANDESITE. Many years ago, a large chunk of the volcano slid away, and this massive avalanche removed the top of Mount Rainier, bringing its height down to 14,00ft. Subsequent eruptions of lave and TEPHRA built up the modern “summit cone” until about as recently as 1,000 years ago.
LAHARS from Mount Rainier pose the most risk to life as about 150,000 people live on top of old LAHAR deposits and such lahars could cause tsunamis capable of producing PYROCLASTIC FLOWS and expelling lava.
The volcanic risk is somewhat mitigated by “lahar-warning signs” and “escape route signs” in Pierce County. 5-10 “shallow” earthquakes, over 2-3 days, take place from time to time, in the region of 13,000ft below the summit., and are thought to be caused by the circulation of hot fluids beneath Mount Rainier. SEISMIC SWARMS are common features at volcanoes and are rarely associated with eruptive activity. A 2009 “swarm” produced the largest number of events of any swarm at Rainier, since “seismic monitoring” began over 2 decades earlier. Yet another swarm was observed in 2011.
Mountain climbing on Mount Rainier is difficult, involving traversing the largest glaciers in the US. Most climbers require 2-3 days to reach the summit and climbing teams demand experience in glacier travel, self-rescue and wilderness travel. About 8,000-13,000 people attempt the climb each year. Mount Rainier is also popular for winter sports —– snowshoeing and cross-country skiing.