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| | Molossian Institute of Volcanology - Lassen Volcanic National Park |
 | | The Lassen volcanic center consists of the ancient Brokeoff (or Mount Tehama) stratovolcano, a 6-km-wide caldera largely filled by a dacitic lava dome field, and peripheral small andesitic shield volcanoes and pyroclastic cones. |
 | | Beginning 400,000 years ago activity shifted to the north flank of Brokeoff, where episodic, more silicic eruptions produced a small caldera and field of a dozen dacitic lava domes along the inferred margin of the caldera, including Bumpass Mountain, Mount Helen, Ski Heil Peak, and Reading Peak. |
 | | The major remnants, Brokeoff Mountain, Mount Diller, Mount Conard, and Diamond Peak, enclose a central depression that marks the position of Brokeoff volcano, which was approximately 3,350 meters (10,921 feet) high, had a basal diameter of approximately 12 kilometers (7.5 miles). |
| www.molossia.org /volcanology/lassen.html (1739 words) |
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