They say about vacations that half the fun is getting there, seeing the
countryside, eating roadtrip food, admiring at the wildlife, and
waving hello to a few of the other volcanoes that are off the beaten
path…and there are many….and I might even visit a few more on the
way back through. But the next planned stop on my “field trip” would
be up to the US Pacific Northwest in Oregon, just east of the
Cascades Range area on northwest edge of the High Lava Plains in a
geological-Disneyland of a volcanic field called Newberry.
Newberry volcano is a large shield volcano with a base diameter of
around 40 km and a volume of 500 cubic km, making it one of the
largest volcanoes in the 48 connected United States. But unlike your
average shield volcano that grows flat and broad by erupting low-
silica and thinnish basaltic to basaltic-andesite lava, Newberry likes to
“mix things up” with its rock composition. The volcano’s broad low-
angle flanks are home to more than 400 cinder cones, but there are
also rhyolite lava domes, obsidian flows, and several sites containing
lava tubes created by large amounts of mafic pahoehoe. Newberry’s
centerpiece is an oval 6 X 8 km summit caldera containing, among
other things, two freshwater lakes. Those lakes are fed in part by geothermal hot springs.
Newberry’s oldest rocks are at least 600,000 years old…a bit older than Etna, but not as old as Yellowstone. Based on measurements and analysis of samples of rock and ash around the
volcano, we can better understand Newberry’s history. The Teepee Draw Tuff, which blankets much of the volcano, is around half a million years old and is believed to be the product of the first of a series of large plinian eruptions that formed the Newberry Caldera. More recently (relatively speaking) sround 12,000 years ago, the South Obsidian Eruptive Episode built a rhyolite dome and laid down a large deposit of pumice. Then about 10,000 years ago near the start of the Holocene, the East Rim Eruptive, a mafic fissure eruption on the east rim of the caldera constructed numerous cones and lava flows. The Interlake Eruptive Episode that happened around 7,300 years ago inside the caldera saw rhyolite magma interacting with groundwater in phreatic eruptions that resulted in pumice cones, a pumice ring, an obsidian flow and lots of tephra. Next, around 5260 BCE, Newberry changed things up again. Fissures opened up on the northwest and south flanks of the volcano as well as the north rim of the caldera. Basaltic andesite lavas prduced cinder cones and extensive lava flows in what is known as the Northwest Fissure Eruptive Episode. By 1450 BCE, rhyolite was trending again in ring-fracture eruptions of flowing obsidian and more pumice cones just south of the caldera’s eastern lake in the aptly named East Lake Eruptive Episode. Finally came the Big Obsidian Eruptive Episode beginning in 480 CE which began with a plinian eruption that deposited the Newberry pumice all over the eastern flank of the volcano and ended with the emplacement of Big Obsidian Flow on the south of the caldera.
I freely confess. I love rhyolite…and I’m not the only one. 🙂
These days, the Newberry volcano is protected as the Newberry National Volcanic Monument as part of the Deschutes National Forest, managed by the US Forestry Service. There are many opportunities for outdoor recreation such as camping, hiking, fishing and hunting, and winter sports. But some of us would rather go there for the volcanoes. One could explore a mile-long lava tube cave at the Lava River Cave interpretive site in the northwest extremities of the volcanic field. hike from the Lava Lands visitors center and climb Lava Butte, or visit the Paulina interpretive visitor center and learn about the geology of Newberry Caldera.
Also, probably due to its variety of geological features, the Newberry volcanic field has been used by NASA to simulate the lunar surface during training for the Apollo missions, and is a popular field training location for students of geology and volcanology.
The one thing a volcano enthusiast might miss, however, is hot lava. This volcano hasn’t erupted like that since the Big Obsidian Flow was emplaced, but that does not mean Newberry isn’t still potentially active. Geologists believe the volcano is situated over a magma body that lies at just 2-5 km depth. In 1981, drilling to a depth of 932 m below the caldera floor, temperatures of 280°C were registered. Today, the volcano is monitored by the USGS Cascades Volcano Observatory.
This week there was no escaping the Search Party. Kelly was the first to find me, though I should have known better than to hide in her backyard. Jesper came soon thereafter, and Glenn bringing up the rear. Where will the virtual hitch-hikers highway take me next? Be here this coming Monday, 23:00 New York Time (03:00 UTC) when I’ll be on a new adventure at a new volcano.