If you head to Sibley Volcanic Regional Preserve above Oakland, you might wonder the same thing as Bay Curious listener Bourke MacDonald: How did a volcano form here and why did it go extinct?Today on the show, we’re going hiking to learn more about this Bay Area geological wonder.

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Reported by Katrina Schwartz. Bay Curious is made by Katrina Schwartz, Suzie Racho and Brendan Willard. Additional support from Erika Aguilar, Jessica Placzek, Kyana Moghadam, Paul Lancour, Carly Severn, Ethan Lindsey, Vinnee Tong and Joe Fitzgerald Rodriguez.