Natural Hazards

Lava-flow hazard zones on Hawai'i Island reflect the long-term hazard of lava flows, not the short term hazard. Rate of lava coverage—not how recently lava covered an area—is the basis of long-term lava flow hazard. Zone 1: "Includes the summits and rift zones of Kīlauea and Mauna Loa (left) where vents have been repeatedly active in historic time." These areas are the most dangerous because all...

The Map Showing Lava-Flow Hazard Zones on Hawai'i Island reflects long-term lava-flow hazards based on geologic data: the behavior of Hawaiian volcanoes over decades to centuries, the distribution and ages of lava flows and volcanic vents, the structure of the volcano, and topography. The map will not be revised until the geologic processes/structures/topography of the volcanoes change enough to...

The Hawaiian shield volcanoes are the largest mountains on Earth. Mauna Kea Volcano rises 13,796 feet (4,205 meters) above sea level but extends about 19,700 feet (6,000 meters) below sea level to meet the deep ocean floor. Its total height is nearly 33,500 feet (10,211 meters), considerably higher than the height of the tallest mountain on land, Mount Everest (Chomolungma in Tibetan) in the...

Very hot!! Here are some temperatures recorded at different times and locations: The eruption temperature of Kīlauea lava is about 1,170 degrees Celsius (2,140 degrees Fahrenheit). The temperature of the lava in the tubes is about 1,250 degrees Celsius (2,200 degrees Fahrenheit). The tube system of episode 53 (Pu'u O'o eruption) carried lava for 10 kilometers (6 miles) from the vent to the sea...

The hazard zones for Hawai'i Island are based on: The locations of probable eruption sites (which are based on past eruption sites) The likely paths of lava flows erupted from those sites (based on topography and the paths of previous lava flows) The frequency of lava flow inundation of an area over the past several thousand years. The hazard zones also take into account structural and topographic...

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 flows ( lahars ) 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...

The town of Portland, Oregon does have most of a Pliocene-Pleistocene volcanic field within its metropolitan boundaries. The Boring Volcanic Field consists of more than 80 cinder cones and small shield volcanoes . The youngest volcano (Beacon Rock) in the Volcanic Field erupted about 57,000 years ago. Since activity began in this area 2.6 million years ago, it is rare for 50,000 years to pass...

Although Mount Rainier has not produced a significant eruption in the past 500 years, it is potentially the most dangerous volcano in the Cascade Range because of its great height, frequent earthquakes , active hydrothermal system , and extensive glacier mantle. Mount Rainier has 25 major glaciers containing more than five times as much snow and ice as all the other Cascade volcanoes combined. If...

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

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)...

The eruptive history of Mount St. Helens began about 40,000 years ago with dacitic volcanism, which continued intermittently until about 2,500 years ago. This activity included numerous explosive eruptions over periods of hundreds to thousands of years, which were separated by apparent dormant intervals ranging in length from a few hundred to about 15,000 years. The range of rock types erupted by...