Long Valley Caldera
United States · Caldera · 37.72, -118.88 · volcano number 323822
Nothing above background is currently reported at this system. For a volcano outside the United States and Japan that means only that it is not in the Smithsonian's weekly report, not that it is quiet.
What this system is
| Type | Caldera |
|---|---|
| Country | United States |
| Position | 37.72, -118.88 |
| Why it is on this list | named supereruption |
Recorded history
NOAA's hazard records hold one significant earthquake at or within 40 km of this volcano since 1980.
The strongest earthquake on record here was magnitude 6.1, on 25 May 1980 (California: Mammoth Lakes).
| Date | What | Where | Toll |
|---|---|---|---|
| 25 May 1980 | magnitude 6.1 earthquake | California: Mammoth Lakes | $2 million damage |
A dash means NOAA recorded no number, not that nobody died. Older entries are fewer because fewer were written down, not because less happened.
Recorded history: NOAA NCEI hazard databases, public domain, retrieved 2026-10-22.
What this rests on
The caldera is about 32 km by 18 km and formed 760,000 years ago in the eruption that laid down the Bishop Tuff.
That sentence is ours. A fuller account, with its own citations, is where to check it. It was a quotation from the Smithsonian Global Volcanism Program until September 2026, when their terms stopped being compatible with a site carrying advertising.
Who watches it
USGS California Volcano Observatory monitors this system and publishes its alert level. https://www.usgs.gov/observatories/calvo
In an eruption, that observatory is the authority. This page follows it; it does not compete with it.
Other systems tracked
Where these numbers come from
National Geophysical Data Center / World Data Service (NGDC/WDS): NCEI/WDS Global Significant Volcanic Eruptions Database. NOAA National Centers for Environmental Information. doi:10.7289/V5JW8BSH Licence: NOAA NCEI: access to this dataset is unrestricted (US federal work, public domain). Positions and eruption records come from that database; the sentence above is ours. Alert levels come from the publishing observatory.