Island of Lava - Deschutes County, Oregon - Oregon Historical Markers on Waymarking.com

One of three signs at Lava Island viewpoint on trail to Lava Island Rockshelter.

Marker Name: Island of Lava
Marker Text: Below is a rugged “island” of lava. It formed 6200 years ago when lava from Lava Butte poured into the Deschutes River channel forcing the river to relocate. The lava was higher in the center, like a loaf of bread, and the river flowed around both sides. The two river channels rejoin approximately a mile downstream.
The island holds many surprises. Twisted junipers and dwarfed pines grow in the midst of rugged volcanic forms. Moist river air sustains delicate ferns and mosses hidden in deep crevasses. Big game animals use the island and its unique streamside vegetation as a winter haven.

Here’s some additional background on the geology at this site. Around 80,000 years ago the Deschutes River was flowing in a channel located about 2 miles to the southeast roughly parallel to Hwy. 97 near The High Desert Museum. Then about 78,000 years ago a large volume flow was erupted from a now buried vent near Mokst Butte. This flow filled the old river channel and flowed northward almost to Redmond and underlies much of Bend. The Deschutes was displaced westward to the western edge of the flow where it began to erode a new channel. At this location the lava flow had backed up a stream channel flowing east out of the Cascades so the river had to cut across the flow to continue northward. Over the next 70,000 years the river cut a canyon along the edge of the flow from north of Sunriver to Bend. Then about 7000 years ago the eruption of Lava Butte sent a flow to the northwest which again filled the river channel from just above Benham Falls to this location. A thin lobe of the Lava Butte Flow contines north along the canyon for another half mile. The Deschutes has again established a new channel, this time along the west edge of the Lava Butte Flow and near this location spills back into the old canyon.
Note that the sign uses 6200 years and I use 7000 years. The difference is that more recent studies have shown that there is a difference between radiocarbon dates (6200 yrs) and calendar years (7000 yrs).

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