Legend
Volcano Map Legend
The sizes of symbols scale with earthquake magnitude, and their color with either the age of the earthquake or its depth, as shown in the legend below, and selected in the Control Panel. Clicking on an earthquake symbol shows its basic information and a link to a page with more details about the individual earthquake.
Control Panel
Volcano Map Panel
Using the tools in this panel you can control the earthquakes shown on the map. The minimum magnitude to plot is selected by the slider. The "Time" and "Depth" determines whether earthquake age or depth are used to color the symbol.
Cross Section
Cross Section
To view events in profile, click "Define X-Section", select two points on the map, drag the box to include events you would like to plot and then click "Plot X-Section." The perspective is looking through the cross section line and into the box.Last 20 Events
| Mag | Time (Local) | Depth (Km) |
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Mount Adams is a potentially active volcano located 50 km east of Mount St. Helens, and is the second highest peak in Washington State. Although it has not had a major eruption in 1,400 years, it is not considered extinct. Thermal anomalies and gas emissions at the summit indicate that Mount Adams is still active.
Except for Mount Shasta, Mount Adams is the largest volcano in the Cascades by volume. Nearly all of its eruptions have consisted of lava flows with little to no tephra. Parts of the main cone consist of rock weakened by hydrothermal alteration. There is potential for large landslides of this altered rock to generate mud flows and lahars that flow far down valleys.
There was a large debris flow avalanche in 1997 at Mount Admas that was well recorded seismically.
More information about Mount Adams from CVO
Background Seismicity
The PNSN operates 3 seismometers near Mount Adams. On average, we locate 3 earthquakes within 10 km of the volcano per decade.
Seismic recordings of the 10/20/97 Debris Avalanche
at Mount Adams, Washington
Photo courtesy of Gifford Pinchot National Forest
At 12:31 AM PDT on October 20, a large mass of rock fell from the Castle, a prominent rock formation east of the summit of Mount Adams. This avalanche was recorded on many seismograph stations of the Pacific Northwest Seismic Network in southern Washington and northern Oregon, and some examples of the seismic signal from five broad-band stations are shown below. The table below the signals indicates where each of the stations are located, and their distance from the avalanche source area on Mount Adams.
| Station | Location | Distance, km |
| COR | Corvallis, Oregon | 230 |
| GNW | Green Mtn., Washington | 183 |
| LON | Longmire, Washington | 66 |
| RAI | Trojan Power Plant, Oregon | 110 |
| RWW | Satsop, Washington | 180 |
The total time window shown is 195 seconds; the signals shown have durations between 80 and 110 seconds. The total time duration of motion for this avalanche is estimated to be about 6 minutes, based on recordings from the closest seismograph station (not shown). The elongated, spindle-like shape of the signals is typical of large avalanches; this characteristic shape helps seismologists to differentiate them from earthquakes, which typically display one or more sharp peaks in amplitude, after which the signal decreases smoothly back to the level of background "noise" typically seen at each station.
The debris avalanche on October 20 followed an earlier sequence of debris avalanches from the Avalanche Glacier on the southwest side of Mount Adams. These avalanches occurred between August 29 and 31, and consisted mostly of ice from the Avalanche Glacier.
For more images and detailed information on the Mount Adams avalanches, see the web pages produced by the Cascades Volcano Observatory.
For more information on the seismic signals generated by large avalanches, see Seismic detection and location of debris avalanches.
This page was created by Bob Norris
(norris@ess.washington.edu)
Last update: 11/05/97.