Geology of Dry Canyon - Oregon Historical Markers on Waymarking.com

At the north trailhead for the Dry Canyon Trail there are two small interpretive kiosks. On kiosk has information on the Redmond Wastewater Treatment Plant. The other kiosk has information (geology, plants, and wildlife) on the Dry Canyon.

NOTE: This sign presents the basic geology of the Dry Canyon but there are many problems with the details in the sign. Some updates to the sign are listed after the text of the sign.

Marker Name: Geology of Dry Canyon
Marker Text: The lava that floors the Dry Canyon is known as Deschutes formation basalt. These are sheet like flows with smooth to ropy-textured upper surfaces. The lava erupted from vents on the north flank of Newberry volcano. The exact vent area is uncertain but would be south (upslope) of US Highway 20 and southeast of Bend. The lava is younger than 780,000 years and much of it in the Bend area is younger than 400,000 years.
Prior to the basalt flows, water in the Dry Canyon was thought to come from melting glaciers in the Forked Horn Butte area. Thus it was a tributary to the Deschutes River.
The lava flowed north across the broad plain extending to Redmond. Beyond Redmond the basalt flowed into Deschutes and Crooked Rivers canyons and, via the Deschutes Canyon reached to Lake Billy Chinook. The flows that entered the Crooked River drainage grew stagnant and solidified at Crooked River Ranch.
The Dry Canyon rim is made up of “Rimrock” basalt which overlays the Deschutes Formation. This is composed of volcanic debris ranging from fine ash to large block as much as 10 feet in diameter.
Lava tubes at the south end of Dry Canyon distributed lava northwesterly into the canyon. The lava was funneled through the canyon and spread out into wide area to the north. The canyon floor was left with a flat surface over the years. This has been overlain by alluvium (soil) built up by the forces of weather and plant life.

UPDATES TO THE SIGN:
The flows on the floor of the canyon are not part ot the Deschutes Formation which ranges in age from 4 to 8 million years old. Instead the flows are from Newberry Volcano which is less than a half million years old. Recent geologic work on this intercanyon flow indicates that it is only about 75,000 years old and comes from a group of small vents west of Horse Butte, south of Bend.
There were no glaciers in the Forked Horn Butte area. Recent geologic work indicates that the prior to about 78,000 years ago the canyon was the main channel of the Deschutes River. At about 78,000 years ago a flow in the Bend area diverted the river westward in to its present channel. Then about 75,000 years ago another eruption sent flows northward which spilled into the old canyon and partially filled it.

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