Images

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.

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

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

Geologic Hazards at Volcanoes (click for larger version)

Mount Scott Lookout seismic and GPS volcano monitoring station, view from the southwest. Near Crater Lake, Oregon.

Deformation monitoring equipment—GPS antenna maintenance on south side of Crater Lake National Park Boathouse on Wizard Island. Oregon

Oblique aerial photograph of source areas and runout paths of some of the devastating debris flows that were responsible for more than 20,000 fatalities in Vargas state, Venezuela, December 1999.

Lava-flow hazard zones map, Island of Hawai‘i. See Full Map for complete legend.

Sampling gas and taking temperature measurements from a fumarole at the summit of Mount Rainier, Washington.

Slope map of Mauna Loa, including lava flows erupted since 1823 (gray), showing the approximate number of hours or days it took for a flow to advance from the vent location to the ocean or maximum reach of a flow. One flow that moved down the steep slopes on west flank of Mauna Loa reached the ocean in as little as 3 hours after the vent started erupting in 1950.

Pyroclastic flow (dense darker grey billowing mass) travels down slope of Mayon volcano, Philippines while ash column rises from the vent. Dilute, lighter-colored ash billows off leading edge.

Map of hazard zones for ground fractures and "small-scale" subsidence for the Island of Hawai‘i. Subsidence and fracturing events are frequent in zone 1, which covers the summit and rift zones of Kīlauea and Mauna Loa volcanoes, but are somewhat less frequent in zone 2, on the south flank of Kīlauea.

The older or original suggested location of this rift is shown with a blue dashed line. Black arrows show one possibility for the westward migration of the Nīnole Hills rift to the location of Mauna Loa's current Southwest Rift Zone (yellow dashed line). The South Kona Slump and ‘Ālika-1 and ‘Ālika-2 landslides are shown off the west coast of the island.

Aerial view of Haleakalā Crater northward to Ko‘olau Gap. Sharp rimmed crater in near ground is Ka Lu‘u o ka ‘Ō‘ō.

Top panel shows a continuous GPS station located in Yellowstone National Park. The antenna is secured to the ground by several metal poles, and a nearby set of solar panels provides power to the station. Lower panel shows a semipermanent GPS station, with a small solar array for power and an antenna located close to the ground.