Answer:
Debris flows
pose the greatest hazard to people near Mount Rainier. A debris
flow is a mixture of mud and rock debris that looks and behaves
like flowing concrete. Giant debris flows sometimes develop when
large masses of weak, water-saturated rock slide from the
volcano's flanks. Many of these debris flows cannot be predicted
and may even occur independently of a volcanic eruption. Giant
debris flows can also form during an eruption as hot rock
fragments tumble down the volcano's slopes, eroding and melting
snow and glacier ice. Although they happen infrequently, giant
debris flows have the potential to inundate much of the southern
Puget Sound lowland. Scientists estimate that debris flows can
travel the distance between Mount Rainier and the Puget Sound
lowland in as little as 30 minutes to a few hours. About 100,000
people now live in areas that have been buried by debris flows
during the past few thousand years.
