North Sister Field
- Status: North Sister Field is monitored by the Cascade Volcano Observatory and is at a background level of activity.
- Volcanic History Overview: North and Middle Sister volcanoes anchor the northern end of the Three Sisters volcano group that dominates the landscape of the central Oregon Cascades. Glaciers have deeply eroded the Pleistocene andesitic-dacitic North Sister stratovolcano, exposing the volcano's central plug. North Sister was constructed over the remnants of the basaltic Little Brother shield volcano to the NW. Middle Sister volcano, also over 3000 m in elevation, is located only 2 km to the south. The basaltic-to-rhyodacitic Middle Sister is less-eroded, but Holocene activity in the North Sister area is restricted to a group of cinder cones north and NW of the North Sister that have produced a series of fresh-looking blocky lava flows on both sides of McKenzie Pass. The youngest lava flow, from Collier Cone, which was erupted about 1600 years ago and traveled 13.5 km to the west, is a prominent feature of the McKenzie Pass area.
- Location: Western US, OR
Elevation: 3074 m
Recent Eruption: 100,000 years ago?
- Hazard Assessments: Scott, et.al., 2001, Volcano Hazards in the Three Sisters Region, Oregon, USGS Open-File Report 99-437.
- Link to monitoring data: The Pacific Northwest Seismic Network
Volcanic Alert Level: NORMAL Aviation Color Code: GREEN