Images

Moderate ash on corn crops from eruption of Tungurahua, Ecuador, 2007.

Due to the cataclysmic eruption of May 18, 1980, many of the locations annotated on this map are now either covered or no longer visible.

Non-volcanic peaks of the North Cascades lie in the background. Dusty Creek drainage experiences regular lahars. Gamma Ridge Formation are hydrothermally altered rocks on left ridge. Loose pyroclastic fill deposits cap right ridge; Eastern view, Glacier Peak, Washington.

Exposed rock ridges are thick Pleistocene lava flows that were confined between large glaciers. Glacier Peak, Washington, view north.

Information regarding volume and rates of advance for the crevassed Crater Glacier at Mount St. Helens, Washington, are extracted from Digital Elevation Models created from aerial photography. The red line shows the extent of Crater Glacier in 2012. Since 2012, the glacier has advanced about 50 m (160 ft) down the Loowit channel.

Summer geology intern Mindy Juergenson climbs over downed lodgepole pine trees killed in the fire of 1988 as she packs a GPS station out of the field (inset). Nine temporary stations are deployed each April/May and retrieved in October/November. The temporary stations supplement a network of permanent stations that record ground deformation data year-round.

Silica sinter (an amorphous form of silicon dioxide) forms from the waters that flow from hot springs near Shoshone Lake, Yellowstone National Park. USGS photograph by Jake Lowenstern.

Old Faithful geyser in eruption at Yellowstone National Park's Upper Geyser Basin.

GPS measurements provide models of the direction and rate (length of arrow) of deformation at the summit of Mauna Loa. Arrows pointing in multiple directions away from the summit indicate inflation.

Erratics located on a cinder cone on the northeast flank of Newberry Volcano, Oregon.

Haleakalā Volcano map showing strata of the HANA Volcanics by age.

CalVO geologists Duane Champion and Drew Downs collect paleomagnetic samples from basalt lava flows at Eagle Lake

Volume of products, eruption cloud height, and qualitative observations (using terms ranging from "gentle" to "mega-colossal") are used to determine the explosivity value. The scale is open-ended with the largest volcanic eruptions in history (supereruptions) given magnitude 8.

HVO seismologists use this to review automatically generated earthquake parameters (location, depth, magnitude), measure P- and S-wave arrival times, and re-compute earthquake hypocenter and magnitudes for cataloging and distribution to the public.

Although numerous intensity scales have been developed over the last several hundred years to evaluate the effects of earthquakes, the one currently used in the United States is the Modified Mercalli Intensity (MMI) Scale. It was developed in 1931 by the American seismologists Harry Wood and Frank Neumann.

Vent activity, typical of that in summer and fall 1969 between episodes of high fountaining. The spattering is from one of two compartments that contained lava. Typically lava levels in the two compartments were different, and gas pistons might work in both but at different times.

Map showing area covered by lava flows of Mauna Ulu eruption. Note that the map was made in 1997, before diacritical marks were being used in Hawaiian place names. The two colors designate the 1969-71 and 1972-1974 parts of the eruption, respectively. In the scale, 3 km is equal to about 2 mi.

Map Showing Outbreak Progression In 1956

Mount St. Helens prior to the catastrophic eruption of May 18, 1980. Streams and lava flows also visible. View is looking southerly from oblique aerial view. Mount Hood in distance.

Mount Baker's crater lake in 1976 formed due to glacial and snow melt as a result of increased heat from magma beneath the surface. Fumarole on left ejecting gas at a velocity of 268 kph (167 mph).

Brimstone Basin, Yellowstone, aerial photo with overlay of two types of altered ground (light blue and pale pink shading) and locations of gas measurements (red dots). 2012 study