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
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Mount Hood is a potentially active volcano, and the highest peak in Oregon State. It is located approximately 75 km ESE of Portland, OR.
In the last 1,500 years, Mount Hood has had two major eruptive periods that produced lava domes, pyroclastic flows and mud flows, and minor ash fallout. The most recent major eruptive period began in 1780 and lasted for one to two decades. Minor eruptive activity was observed during the mid-19th century. Rapid melting of snow and glacier ice by pyroclastic flows can generate large lahars that race down river valleys.
More information about Mount Hood
Background Seismicity
The Cascades Volcano Observatory and the PNSN cooperatively operate 6 seismometers on or near Mount Hood. On average, we locate 0 to 3 earthquakes within 10 km of the volcano each week.
Brief Summary of 1990s Seismicity at Mount Hood
Seismicity at Mount Hood is primarily characterized by fairly intense swarms of micro-earthquakes which typically occur about 4 to 7 km south of the summit. Over three quarters of the roughly 250 earthquakes which have been located at Mount Hood during the 1990s have occured in these swarms. These swarms usually last from a few hours to a couple of days and have had as many as 50 well located earthquakes and as few as 4. The largest event in a swarm usually does not occur at the beginning (such as a main shock-after shock sequence). The largest event in the roughly 15 sequences during the 1990s have varied from M=1.6 to M=3.5.
All of the earthquakes in the Mount Hood sequences have characteristic waveforms similar to tectonic earthquakes. Swarms of these types of events are fairly common on many volcanos. These are in contrast to low-frequency volcanic earthquakes which have a very different character and may be indicators of a possible eruption. The Mount Hood events likely are occurring on a fault or fault system located to the south of the volcano and represent either its reaction to regional tectonic stresses or possibly deep-seated volcanic stress below the region. Volcanic history and details of Mount Hood is summarized by pages at the Cascade Volcano Observatory.
Description of the earthquake swarm at Mount Hood in January, 1999:
An earthquake swarm began near Mount Hood in northern Oregon early Monday morning (Jan 11, 1999) and produced more than two dozen earthquakes that day, the largest of which were magnitudes 3.2 (at 2:04 pm PST) and 3.0 (at 8:54 am PST). Following a pause in activity on Tuesday and Wednesday, another magnitude 3.2 earthquake occurred at 3:56 am PST Thursday (Jan. 14, 1999), followed by a magnitude 3.0 earthquake at 8:13 am PST. The largest earthquakes were felt at Timberline, Brightwood, Parkdale, and Mount Hood Meadows. As of noon on Jan. 14, we had detected 66 earthquakes, 33 that are large enough to be well located.