Newberry National Volcanic Monument. Or, An Excuse to Post Lots of Pictures of Rocks.
Newberry National Volcanic Monument surrounds the area of Newberry volcano and includes lava flows, obsidian fields, cinder cones surrounding volcanic vents, and a lava tube. From the highest point in the park, Paulina Peak, it is possible to see one of the larger lava flows, frozen in the characteristic swirl pattern. The picture below also shows a large area of the caldera, or top of the volcano that collapsed 75,000 years ago. Parts of the caldera are filled with water fed by active hot springs.
Within a mile of this lava field is a newer obsidian flow (named “The Big Obsidian Flow”) that was created by rapidly cooling magma that did not have the chance to crystallize, or organize the silica molecules into structures. This square mile of black glass is intermixed with the pumice that was ejected from the depths of the volcano during the violent eruption. Unlike the dense, smooth glass, the air-filled pumice rock is a result of the nearly instantaneous depressurization and cooling of the lava. Nearly 150 feet higher than the surrounding landscape, the obsidian and pumice field ends abruptly, drawing contrast between the black rock and the green forest. Oh, and did I mention I got to hike through it?!?! Unfortunately, with the sun high overhead the photos are washed out and do not do it justice: it’s indescribably amazing to walk through chunks of black, shiny rocks.
Another lava field just north shows evidence of how a fast-moving fluid eruption 7,000 years ago engulfed a forest, leaving behind molds of trees that were burned in place. As the trees burned, the moisture in the wood was released, cooling the lava around them and forming the casts. Some of these molds are up to 15 feet deep and still show the pattern of the bark.
Lava Butte, located to the northeast, resembles a small volcano but is actually just a cinder cone or a volcanic vent around which is spewed pumice. After the vent expelled the rock, which built up the sides to over 500 feet, the remaining magma oozed out as a thick lava.
The last thing I saw at the monument was the Lava River Cave, a lava tube much like the one seen at Mount St. Helens where a swift lava flow cooled on top creating a crust that enclosed the lava channel underneath. This time I was able to use the flash on my camera but with no ambient light the flash was still not powerful enough to illuminate much of the cave at one time. In addition, because of the high silica content of the hardened lava, there is a lot of reflection created. What I was able to capture fairly well was the variety of textures and colors on the walls of the tube created by deposits of minerals, erosion by the heat, and striations from rocks being carried in the later lava flows.