This year, I have written several stories about the volcanoes of the Cascade Range in the Pacific Northwest, including Mt. Adams, Mt. St. Helens, and Mt. Rainier.
Yet few people are aware of the largest volcano in the Cascades: Newberry Volcano, which is a volcanic arc that covers an area the size of Rhode Island. The United States Geological Survey considers it a “high threat volcano,” since it is still active and capable of producing explosive eruptions.
Throughout its lifetime, Newberry has been the most explosive volcano in the Cascades, with at least 5 caldera-forming eruptions in less than 300,000 years. The most recent caldera developed about 65,000 years ago, when explosive eruption of basaltic andesite to rhyolite created the current 6 x 8 km (3.7 x 5 miles) caldera.
Several eruptions have occurred in the caldera since the last glacier melted nearly 12,000 years ago, the youngest of which, about 1,300 years old, produced the Big Obsidian Flow and a tephra that has been found in Idaho
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