Lava flows constitute only one of the numerous hazards associated with volcanic eruptions.
The West Coast sits atop the Ring of Fire, an unstable zone lining the boundaries of the Pacific Ocean where earthquake and volcanic activity occur regularly. Volcano dangers include surges of hot ash and gases called pyroclastic flows; lahars, which are landslides with a water component; lava flows; blast effects similar to the detonation of a bomb; and barrages of hot ash and steam. People underestimate the power and speed of volcanoes.
Kilauea
A devastating eruption of Kilauea in the late 18th century, considered the most deadly in the United States, killed at least 80 people. In 1924, Kilauea came alive once again, vomiting volumes of debris, with some pieces weighing close to 8 tons. Explosive eruptions occur on Kilauea only when lava within the crater at the volcano's summit, the summit caldera, meets groundwater, spewing steam and hot gases.
Mauna Loa
The title of world's biggest volcano belongs to Mauna Loa, which envelops an area measuring half the size of Hawaii. The last significant eruption of this behemoth occurred in 1984, but in 2002, activity resumed at Mauna Loa's summit caldera. Geologists note that the caldera appears to be rising and enlarging, possibly indicating an imminent eruption. Although Kilauea has been exhibiting more volcanic activity, Mauna Loa can potentially produce greater damage because it produces more lava per eruption.
Mount Rainier
Mount Rainier houses 25 glaciers, which can form fast-moving lahars.
Mount Rainier, nestled within the Cascade Mountains, presents a different hazard from other volcanoes, where pyroclastic flows generally dominate. The next eruption of the Cascade Mountains's tallest peak could send lahars down the mountain when hot lava melts portions of the 25 substantial pieces of ice called glaciers that cover the top of Mount Rainier. Lahars from Rainier could reach Washington's Puget Sound.
Mount St. Helens
Mount St. Helens erupted in 1980, killing 57 people.
Every 100 to 200 years since the 1400s, Mount St. Helens erupts. The most recent eruption was May 18, 1980. The eruption blew 400 m of volcanic material off the north side of the mountain. The accompanying blast annihilated all objects within 12 km of the volcano. The eruption, one of the most costly volcanic events in the United States, resulted in 57 deaths and a billion dollars in damage.
Novarupta
Within four hours of its eruption, Novarupta ejected an enormous volume of ash into the atmosphere, forming a dark plume 20 miles above Alaska. The ash caused breathing difficulties in humans, contaminated water supplies, rendered radio communication useless and destroyed buildings. Plants and organisms lower on the food chain died in large numbers; a cascade of death befell organisms dependent on those plants and animals.
Redoubt Volcano
Redoubt last erupted in 1990, but volcanic and seismic activity as recent as 2009 suggest that the volcano is reawakening. If Redoubt erupts again, its ash plume could blanket the skies over Alaska, confusing aircraft and deactivating their engines. Since 1778, Redoubt has exploded violently five times, ejecting ash into the atmosphere, producing pyroclastic flows and lahars and initiating flooding episodes.
Tags: Mount Rainier, Mount Helens, pyroclastic flows, Cascade Mountains, flows lahars, into atmosphere
