Images

Mount Hood lies approximately 70 km (45 mi) from Portland International Airport. Ash can cause jet engines to fail, and air traffic may be grounded during an eruption.

Timeline for eruptions at Mount Baker during the Holocene (12,000 years ago to present).

Potential volcanic hazards at Mount Baker.

Note the protruding logs and branches from living trees that were knocked down and carried by the lahar. Ice axe, 3 ft, shows scale. Lahars are the greatest hazard at Mount Baker.

Map of volcanic ashfall. Areas of the United States that once were covered by volcanic ash from Yellowstone's giant eruptions 2 million and 630,000 years ago, compared with ashfall from the 760,000-year-old Long Valley caldera eruptions at Mammoth Lakes, California, and the 1980 eruption of Mount St. Helens, Washington.

Craters of the Moon, Idaho, Landsat 7 true-color image viewed from the east. Pioneer Mountain Range along the western border. Image created by NASA EArth Observatory.

Cutaway views showing the internal structure of the Earth. Left: To scale drawing shows that Earth's crust is very thin. Right: Not to scale, more detail of three main layers (crust, mantle, core).

Photograph from the southwestern wall of the Grímsvötn caldera in Vatnajökull on December, 19 1998.

USGS geochemist Bill Evans measures the temperature of a superheated (hotter than the boiling point) fumarole in Lassen Volcanic National Park.

Profile of Mauna Kea showing inferred contact (dot-dashed line) between postshield-stage Hamakua Volcanics and underlying shield-stage lavas. Approximate contact with Laupahoehoe Volcanics dashed.

Geologic map of Mauna Kea, showing generalized distribution of lava flows, cinder cones, and glacial deposits of the Laupahoehoe Volcanics.

During prevailing trade wind conditions, the nearly constant stream of volcanic smog (vog) produced by Kīlauea Volcano on the Island of Hawai‘i is blown to the southwest and west. The trade winds (blue arrows) blow the vog from its main source on the volcano (white plume) to the southwest, where wind patterns send it up the island's Kona coast.

Volcanic gases react with the atmosphere in various ways; the conversion of sulfur dioxide (SO2) to sulfuric acid (H2SO4) has the most significant impact on climate.

An aerial view looking south of the Long Valley volcanic region in the area of Mono Lake, showing a line of rhyolite lava domes and explosion craters. An inset map shows the locations of silcic magmatic centers in the Long Valley area.

Geologic map of Mauna Kea with generalized surface distribution of Hamakua Volcanics. Laupahoehoe Volcanics are inferred to overlie a vast area of Hamakua Volcanics on the upper flanks and summit.

Rock and ice debris avalanche (October 20, 1997) on the east side of Mount Adams.

A tumulus in the Coso Volcanic Field, California. This lava was probably more viscous than the lava found in the Hawaii tumuli.

Detail of levee on an active channelized aa flow. Note the pahoehoe overflows in the levees and the level of the active flow below the tops of the levees. This lower flow level is not allowed in the commonly used "Bingham" model of lava flows.

Mt. Konocti erupted during the most recent stage of volcanism (01. Ma to 10,000 years ago), and a future eruption from the same site would be devastating to the nearby inhabitants.

Photograph of the large jökulhlaup that spread out across Skeiðarársandur (glacial outwash plain) from the terminus of Skeiðarárjökull, an outlet glacier of Vatnajökull.

Lava fragments explode onto the sides of a littoral cone on the south coast of Kīlauea Volcano as lava pours into the sea from a lava tube.