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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Three Sisters are a cluster of volcanoes, composed of North Sister, Middle Sister, and South Sister. They are located approximately 25 km SW of Sisters, OR.
North Sister is considered extinct, and Middle Sister has not erupted for 14,000 years. South Sister is the youngest volcano, and erupted explosively about 2,000 years ago. It has erupted lavas ranging from basaltic andesite through rhyolite. In 2001, uplift of almost 30 cm was detected in an area 5 km W of South Sister. This uplift was accompanied by a seismic swarm in 2004, raising concern of renewed activity. By 2007, uplift had slowed and seismic activity returned to background levels.
More information about Three Sisters
Background Seismicity
The Cascades Volcano Observatory, University of Oregon, and the PNSN cooperatively operate 10 seismometers on or near Three Sisters. On average, we locate 0 to 3 earthquakes within 10 km of the volcano each year.