Episode 1843
Geology of the Lassen volcanic area
Sun, 2022-May-22 00:30 UTC
Length - 3:22
Direct Link
Welcome to featured Wiki of the Day where we read the summary of the featured Wikipedia article every day.
The featured article for Sunday, 22 May 2022 is Geology of the Lassen volcanic area.
The geology of the Lassen volcanic area presents a record of sedimentation and volcanic activity in the area in and around Lassen Volcanic National Park in Northern California, U. S. The park is located in the southernmost part of the Cascade Mountain Range in the Pacific Northwest region of the United States. Pacific Oceanic tectonic plates have plunged below the North American Plate in this part of North America for hundreds of millions of years. Heat from these subducting plates has fed scores of volcanoes in California, Oregon, Washington and British Columbia over at least the past 30 million years, including these in the Lassen volcanic area.
Between 3 and 4 million years ago, volcanic-derived mud flows called lahars streamed down several major mountains that included nearby but now extinct Mount Yana and Mount Maidu to become the Tuscan Formation. Basaltic and later andesitic to dacitic flows of lava covered increasingly larger areas of this formation to eventually form the lava plateau that the park sits on. About 600,000 years ago, Mount Tehama started to rise as a stratovolcano in the southwestern corner of the park, eventually reaching an estimated 11,000 ft (3,400 m) in height.
Roughly 27,000 years ago, a dacite lava dome quickly pushed its way through Tehama's former north-eastern flank, becoming the approximately 1,000 ft (300 m) shorter Lassen Peak. Lassen's shape was significantly altered by glacial erosion from 25,000 to 18,000 years ago during the Wisconsin glaciation. Since then, smaller dacite domes such as the 1,100-year-old Chaos Crags have formed around Lassen. Phreatic (steam explosion) eruptions, dacite and andesite lava flows along with cinder cone formation have persisted into modern times. Most notable of these is the eruption and formation of Cinder Cone in the mid to late 17th century and the eruption of Lassen Peak in the early 20th century. The only activity since then has been the constant bubbling of mud pots and steaming of fumaroles from the various geothermal areas in Lassen Volcanic National Park. The potential exists for renewed vigorous volcanic activity that could threaten life and property in the area.
This recording reflects the Wikipedia text as of 00:30 UTC on Sunday, 22 May 2022.
For the full current version of the article, see Geology of the Lassen volcanic area on Wikipedia.
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