How old is Mount St. Helens?

Deadliest Volcanic Eruptions Since 1500 A.D. Eruption Year Casualties Major Cause Nevado del Ruiz, Colombia 1985 25,000 1,3 Mudflows 3 Mont Pelée, Martinique 1902 30,000 1 (29,025) 2 Pyroclastic flows 2 Krakatau, Indonesia 1883 36,000 1 (36,417) 2 Tsunami 2 Tambora, Indonesia 1815 92,000 1,2 Starvation 2 Unzendake, Japan 1792 15,000 1 (14,030) 2 Volcano collapse, Tsunami 2 Lakagigar (Laki)...

The May 18, 1980 eruptive column at Mount St. Helens fluctuated in height through the day, but the eruption subsided by late afternoon. By early May 19, the eruption had stopped. By that time, the ash cloud had spread to the central United States. Two days later, even though the ash cloud had become more diffuse, fine ash was detected by systems used to monitor air pollution in several cities of...

Before May 18, 1980, Mount St. Helens' summit altitude of 9,677 feet (2,950 meters) made it only the fifth highest peak in Washington State. It stood out handsomely, however, from surrounding hills because it rose thousands of feet above them and had a perennial cover of ice and snow. The peak rose more than 5,000 feet (1,524 meters) above its base, where the lower flanks merge with adjacent...

During the 9 hours of vigorous eruptive activity on May 18, 1980, about 540 million tons of ash from Mount St. Helens fell over an area of more than 22,000 square miles (57,000 square kilometers). The total volume of the ash before its compaction by rainfall was about 0.3 cubic mile (1.3 cubic kilometers), equivalent to an area the size of a football field piled about 150 miles (240 kilometers)...

Eruptions of Mount Rainier usually produce much less volcanic ash than do eruptions at Mount St. Helens. However, owing to the volcano's great height and widespread cover of snow and glacier ice, eruption triggered debris flows ( lahars) at Mount Rainier are likely to be much larger--and will travel a greater distance--than those at Mount St. Helens in 1980. Furthermore, areas at risk from debris...

Some Native Americans of the Pacific Northwest variously called Mount St. Helens 'lawilátɬa ', or 'one from whom smoke comes'. The volcano lawilátɬa is listed (as Lawetlat’la) on the National Register of Historic Places and acknowledged as a Traditional Cultural Property of significance to the Cowlitz Indian Tribe and Confederated Tribes and Bands of the Yakama Nation. The modern name, Mount St...

Eruptions in the Cascades have occurred at an average rate of one to two per century during the last 4,000 years. Future eruptions are certain. Learn more: Eruptions in the Cascade Range During the Past 4,000 Years USGS Cascades Volcano Observatory

The world's largest eruption of the 20th century occurred in 1912 at Novarupta on the Alaska Peninsula in what is now Katmai National Park and Preserve. An estimated 15 cubic kilometers of magma was explosively erupted during 60 hours beginning on June 6th. This volume is equivalent to 230 years of eruption at Kilauea (Hawaii) or about 30 times the volume erupted by Mount St. Helens (Washington)...

Excluding steam eruptions, these volcanoes have shown activity: Mount St. Helens, Washington - Eruptions and/or lava dome growth occurred in the late 1700s, 1800-1857, 1980-1986, and 2004-2008. Lassen Peak, California - A series of steam blasts began on May 30, 1914. An eruption occurred 12 months later on May 21, 1915. Minor activity continued through the middle of 1917. Mount Hood, Oregon -...

The May 18, 1980 eruption of Mount St. Helens (Washington) was the most destructive in the history of the United States. Novarupta (Katmai) Volcano in Alaska erupted considerably more material in 1912, but owing to the isolation and sparse population of the region, there were no human deaths and little property damage. In contrast, the eruption of Mount St. Helens caused loss of lives and...

More than 80 percent of the Earth's surface--above and below sea level--is of volcanic origin. Gaseous emissions from volcanic vents over hundreds of millions of years formed the Earth's earliest oceans and atmosphere, which supplied the ingredients vital to evolve and sustain life. Over geologic eons, countless volcanic eruptions have produced mountains, plateaus, and plains, which subsequently...

The United States ranks third, behind Indonesia and Japan, in the number of historically active volcanoes (that is, those for which we have written accounts of eruptions). In addition, about 10 percent of the more than 1,500 volcanoes that have erupted in the past 10,000 years are located in the United States. Most of these volcanoes are found in the Aleutian Islands, the Alaska Peninsula, the...