Mount Mazama erupts and forms the Crater Lake caldera
- environment
- indigenous histories
- disasters
**Historical setting:** 5700 BCE · Oregon and the wider Oregon Country. A major eruption transforms the mountain into a caldera later occupied by Crater Lake. Klamath oral traditions preserve relationships with this landscape. The approximate date describes the eruption, not the beginning of Indigenous knowledge or the park’s later establishment. **Historical date:** approximately 5700 BCE. **Precision:** year. Proleptic Gregorian BCE/CE calendar, UTC plotting coordinates. A year-only date uses January 1 as an anchor, not an asserted exact day; a month-only date uses its first day. There is no historical year zero. Events in English colonies before the 1752 calendar change generally use year-only anchors, avoiding silent reuse of Julian Old Style days as Gregorian. Archaeological ages are approximate and are not exact arrival dates. Mount Mazama’s eruption transforms the mountain through a caldera-forming geological event. The lake and the cultural relationships associated with it develop within that changed setting. Geological dating and Klamath oral traditions illuminate different aspects of the landscape without one being reduced to a park-era origin story. **Sources:** - [Oregon Secretary of State : Chronological History of Oregon : Explore Oregon : State of Oregon](https://sos.oregon.gov/blue-book/explore/pages/chronology-prehistory.aspx) - [History & Culture - Crater Lake National Park (U.S. National Park Service)](https://www.nps.gov/crla/learn/historyculture/index.htm) **Image:** Lukep913 · Crater Lake panorama.jpg · CC BY 3.0. Image date record: 2009-11-04. Later photograph of Crater Lake; it does not depict the ancient eruption. No changes beyond thumbnail scaling. [File and attribution](https://commons.wikimedia.org/wiki/File:Crater_Lake_panorama.jpg); [license](https://creativecommons.org/licenses/by/3.0).
- Date precision
- approximate year
- Coordinate convention
- Proleptic Gregorian BCE/CE calendar, UTC plotting coordinates. A year-only date uses January 1 as an anchor, not an asserted exact day; a month-only date uses its first day. There is no historical year zero. Events in English colonies before the 1752 calendar change generally use year-only anchors, avoiding silent reuse of Julian Old Style days as Gregorian. Archaeological ages are approximate and are not exact arrival dates.
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