The eruption created the caldera that now holds Crater Lake the deepest lake in North America. Other composite volcanoes include Mount Fuji in Japan and Mount Rainier and Mount St. Helens, both of which belong to the Cascades Range. The Three Sisters, part of the Cascades Range, threaten several nearbye towns. When composite cone volcanoes erupt, they can generate pyroclastic flows, one of the most dangerous volcanic hazards. Although these flows rarely travel more than 6 miles away from the volcano, high speeds and temperatures reaching into the hundreds of degrees make them particularly dangerous to life and property.
Pyroclastic flows can trigger other hazards, as well.
On their way downhill, these steamy mixtures melt snow and glacier ice, creating lahars, watery blends of volcanic rocks and mud that surge down riverbeds like rapidly flowing concrete. Lahars can devastate valley floors tens of miles from volcanoes and gush downhill so quickly that people might not have time to evacuate. Composite cone volcanoes, such as South Sister and Middle Sister, possess several hazards. Less explosive eruptions would result in lava flows, masses of molten rock that pour onto the Earth's surface during an eruption. When considering volcanic risks, most people think of lava.