Photo from Windy Point: I'm standing next to 50,000 year old basaltic andesite from Black Crater (foreground, age approximate), looking across a 2,900-year-old basaltic andesite flow from Little Belknap (dark flows beyond the foreground trees), at the snow-capped peak of the 300,000- to 35,000-year-old Mt. Jefferson stratovolcano (Windy Point location, MSRMaps).
(If you don't know what observatory I'm speaking of, then you need to read on — and then you need to go there: you go down there — I mean, up there.)
Our third stop on the seventh day (after the rock garden stop) was in the town of Sisters, Oregon, where we had lunch indoors, and ice cream outdoors. The clouds were threatening when we arrived. They had cleared some by the time we left, but had regrouped before our fourth stop...
...at the Dee-Wright Observatory on top of McKenzie Pass (Google Maps). That's a view of Black Crater behind the sign — it's a partly glaciated shield volcano that extruded basaltic andesite flows about 50,000 years ago (see Cashman et al, 2009*).
At Dee Wright, you either climb steep stairs made of basalt (or basaltic andesite) or you walk a paved, gentle incline.
More than half way up, you come to a circular room with windows looking off in several specific directions. Each window frames a particular volcano; this is Mt. Jefferson.
It's worth going all the way to the top of the observatory for the view, and also to see this bronze "peak finder." According to long-time residents, this compass — which points to many but not all of the volcanoes visible from the top — has had to be replaced more than once. If you read the arrow in front of the snow-covered mountain on the horizon, you'll see that it's pointing to the North Sister, 6.6 miles distant, 10,094 feet elevation (according to the bronze plaque; according to the Dee Wright Observatory page at the CVO , the elevation is 10,085 feet). The Middle Sister, youngest of the three, is just right of the North Sister; Little Brother (the oldest) is on the right edge of the photo.
The Dee Wright Observatory is built on basaltic andesite flows that erupted from the base of Yapoah Crater, a 2,000 year B.P. cinder cone on the north flank of the North Sister (Cashman et al, 2009). The cone is visible but hard to point out from this angle.
Off to the northeast, the light brown volcano on the left is Belknap Crater, a basaltic andesite to andesite shield volcano that erupted 2,635 to 1,500 years B.P. Little Belknap is the dark point right of Belknap near the right edge of the photo. It erupted basaltic andesite about 2,900 years B.P. (these dates are from Cashman et al, 2009). The dark flows in the distance, behind a narrow swath of trees, are from Little Belknap; they flowed around a patch of older volcanic material (green area roughly in the center), forming what is called a kipuka (as seen in Cashman et al, 2009; USGS definition).
UPDATE: Read more about kipukas at Geotripper, who is currently in Hawai'i!
On the way down, a flock of small brownish birds with yellow colorings — possibly pine siskins — were hanging out amongst the basaltic flow rock.
If you drive a little ways to the west, you can look up toward the North Sister along a treeless flow from Yapoah Crater, the relatively barren cinder cone that barely sticks up above the mostly tree-covered skyline on the left side of the photo. It appears to have a white patch of snow on it's north side. In this Google Street View, Yapoah Crater is just left of the centered tree.
And you already know what we did after the field trip: we went to the Terrebonne Depot, had a great meal and good ale.
Main References:
Cashman, K.V., Deligne, N.I., Gannett, M.W., Grant, G.G., and Jefferson, Anne*, 2009, Fire and Water: Volcanology, Geomorphology, and Hydrogeology of the Central Cascades and Adjacent Areas, Oregon: Geological Society of America, Field Guide 15 (field trip no. 409).
*Anne Jefferson, who blogs at Highly Allochthonous, sent me a copy of this field guide, which I used extensively during this portion of our road trip. Thanks, Anne!
USGS Cascades Volcano Observatory.
Trip report to be continued... not necessarily in a timely fashion.
(If you don't know what observatory I'm speaking of, then you need to read on — and then you need to go there: you go down there — I mean, up there.)
Our third stop on the seventh day (after the rock garden stop) was in the town of Sisters, Oregon, where we had lunch indoors, and ice cream outdoors. The clouds were threatening when we arrived. They had cleared some by the time we left, but had regrouped before our fourth stop...
...at the Dee-Wright Observatory on top of McKenzie Pass (Google Maps). That's a view of Black Crater behind the sign — it's a partly glaciated shield volcano that extruded basaltic andesite flows about 50,000 years ago (see Cashman et al, 2009*).
At Dee Wright, you either climb steep stairs made of basalt (or basaltic andesite) or you walk a paved, gentle incline.
More than half way up, you come to a circular room with windows looking off in several specific directions. Each window frames a particular volcano; this is Mt. Jefferson.
It's worth going all the way to the top of the observatory for the view, and also to see this bronze "peak finder." According to long-time residents, this compass — which points to many but not all of the volcanoes visible from the top — has had to be replaced more than once. If you read the arrow in front of the snow-covered mountain on the horizon, you'll see that it's pointing to the North Sister, 6.6 miles distant, 10,094 feet elevation (according to the bronze plaque; according to the Dee Wright Observatory page at the CVO , the elevation is 10,085 feet). The Middle Sister, youngest of the three, is just right of the North Sister; Little Brother (the oldest) is on the right edge of the photo.
The Dee Wright Observatory is built on basaltic andesite flows that erupted from the base of Yapoah Crater, a 2,000 year B.P. cinder cone on the north flank of the North Sister (Cashman et al, 2009). The cone is visible but hard to point out from this angle.
Off to the northeast, the light brown volcano on the left is Belknap Crater, a basaltic andesite to andesite shield volcano that erupted 2,635 to 1,500 years B.P. Little Belknap is the dark point right of Belknap near the right edge of the photo. It erupted basaltic andesite about 2,900 years B.P. (these dates are from Cashman et al, 2009). The dark flows in the distance, behind a narrow swath of trees, are from Little Belknap; they flowed around a patch of older volcanic material (green area roughly in the center), forming what is called a kipuka (as seen in Cashman et al, 2009; USGS definition). UPDATE: Read more about kipukas at Geotripper, who is currently in Hawai'i!
On the way down, a flock of small brownish birds with yellow colorings — possibly pine siskins — were hanging out amongst the basaltic flow rock.
If you drive a little ways to the west, you can look up toward the North Sister along a treeless flow from Yapoah Crater, the relatively barren cinder cone that barely sticks up above the mostly tree-covered skyline on the left side of the photo. It appears to have a white patch of snow on it's north side. In this Google Street View, Yapoah Crater is just left of the centered tree.And you already know what we did after the field trip: we went to the Terrebonne Depot, had a great meal and good ale.
Main References:
Cashman, K.V., Deligne, N.I., Gannett, M.W., Grant, G.G., and Jefferson, Anne*, 2009, Fire and Water: Volcanology, Geomorphology, and Hydrogeology of the Central Cascades and Adjacent Areas, Oregon: Geological Society of America, Field Guide 15 (field trip no. 409).*Anne Jefferson, who blogs at Highly Allochthonous, sent me a copy of this field guide, which I used extensively during this portion of our road trip. Thanks, Anne!
USGS Cascades Volcano Observatory.
Trip report to be continued... not necessarily in a timely fashion.
