Meager massif covering stable sections of the Pemberton Valley in a debris flow is estimated at one in 2,400 years. There is no sign of volcanic activity with these events. However scientists warn the volcano could release another massive debris flow over populated areas any time without warning. In the past, Mount Rainier has had large debris avalanches, and has also produced enormous lahars due to the large amount of glacial ice present. Its lahars 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. This massive avalanche of rock and ice took out the top of Rainier, bringing its height down to around . About 530 to 550 years ago, the Electron Mudflow occurred, although this was not as large-scale as the Osceola Mudflow. While the Cascade volcanic arc (a geological term) includes volcanoes such as the Mount Meager massif and Mount Garibaldi, which lie north of the Fraser River, the Cascade Range (a geographic term) is considered to have its northern boundary at the Fraser. Largest eruptions The table below lists some of the greatest eruptions to have occurred in the Cascade chain. Human history Native Americans have inhabited the area for thousands of years and developed their own myths and legends concerning the Cascade volcanoes. According to some of these tales, Mounts Baker, Jefferson, Shasta and Garibaldi were used as refuge from a great flood. Other stories, such as the Bridge of the Gods tale, had various High Cascades such as Hood and Adams, act as god-like chiefs who made war by throwing fire and stone at each other. St. Helens with its pre-1980 graceful appearance, was regaled as a beautiful maiden for whom Hood and Adams feuded. Among the many stories concerning Mount Baker, one tells that the volcano was formerly married to Mount Rainier and lived in that vicinity. Then, because of a marital dispute, she picked herself up and marched north to her present position. Native tribes also developed their own names for the High Cascades and many of the smaller peaks, the most well known to non-natives being Tahoma, the Lushootseed name for Mount Rainier. Mount Cayley and The Black Tusk are known to the Squamish people who