Deschutes County, Oregon, USA (July 2012)
The Big Obsidian Flow has an appropriate albeit unimaginative name for this geological structure in central Oregon, just east of the Cascades. It is indeed a big obsidian flow.
It forms part of the vast Newberry National Volcanic Monument, founded in 1990 within the Deschutes National Forest, and specifically within the Newberry Caldera unit. Getting there from Bend, Oregon shouldn’t be difficult. Simply drive south along Highway 97 a little more than twenty miles, then head east on County Road 21 for another fifteen miles, and then arrive. The trip will take about an hour (map).
The Big Obsidian Flow falls within the larger Newberry Caldera, and originated during a period known as the Big Obsidian Eruptive Episode that happened around 1,500 years ago. A fissure opened on the southern edge of the volcanic caldera and magma flowed over an area of approximately 1.1 square miles.
Nothing can grow on these barren rocks even fifteen centuries later. The flow, when viewed from Paulina Peak, looks nearly identical to when it first pushed out from the edge of the caldera and cooled. This youngest lava flow in Oregon serves as a reminder that a large portion of Oregon remains actively volcanic.
Take the Trail
The U.S. Forest Service constructed a trail through the Big Obsidian Flow that covers about seven-tenths of a mile in a loop. This easy trail should take an hour-or-less depending on how often one stops to read the interpretive signs or admire the scenery.
While relatively safe, well marked and with manageable elevation changes, hikers must still take care on the trail. Obsidian consists of a volcanic glass with exposed sharp edges and it can be found everywhere within the flow. It is sharper than surgical steel and it can cut through flesh with ease. Navigating through the flow without a pre-cleared trail would be practically impossible. Visitors must wear closed shoes and dogs cannot be walked through here for safety reasons.
Take it easy and everything will be fine. Wander away from the trail or run through it too quickly and it could be rather dangerous if someone should slip or grab a rock to prevent a fall.
Obsidian
Other volcanic rocks form more commonly than obsidian. Even at this spot — named explicitly for the material — obsidian composes only about ten percent of the flow with the remainder being pumice. Still, large outcroppings of obsidian can be found throughout the flow, and impress visitors with their size and purity.
The obsidian here takes on a typical jet black color denoting its particular purity. Native Americans valued obsidian for its ability to be fashioned into cutting tools, and this became a prime quarrying spot. Pre-Columbian inhabitants traded obsidian from this location throughout the Pacific Northwest by way of the Columbia River.
Leave a Reply