California's Supervolcano Nearly Erupted in 1982; The 3 Magmatic Intrusions 

Note: This is a long comment answering every question you might have regarding today’s video, including some context. I recommending reading it all to understand what I’m saying and to not take my statements out of context. And no, this region of California (Mammoth Mountain, Mono Inyo, Mono Lake, and Long Valley Caldera) is not under any threat of a volcanic eruption anytime soon as of September 29th, 2023. I know that what I’m stating in today’s video might be considered controversial by some. Specifically that in 1982, the Long Valley Caldera (supervolcano) was at one point only 4 months away from erupting. But it of course did not erupt, with magma stalling at 4 km depth. My 4 month figure assumes that my interpretation of the maximum rate of magmatic uplift in 1982 was correct, when magma was at only 4 km depth. For a long time it was thought that this specific intrusion occurred beneath Mammoth Mountain and not Long Valley. I even stated as much in prior videos. However, much like on my opinion involving what caused the Younger Dryas, I looked further into various sources, and changed my opinion. (In the case of the younger dryas, I previously believed that a widespread airburst event caused it. However upon reading new evidence, the widespread burning the younger dryas experienced can be explained without an impact event occurring, so I am now of the opinion that the Younger Dryas was not caused by numerous meteorites exploding in airbursts). I do not simply change my opinion because a single scientific paper mentions something, as we scientists disagree on some topics all the time. However, in this case, after pondering long about this subject I came to the conclusion that the model of the 1981-1982 intrusion occurring within Long Valley and not Mammoth Mountain best fits the data recorded during that time and subsequent analysis. Q: So, am I of the opinion that a powerful eruption was 4 months away at the Long Valley Caldera? A: Absolutely not. While an eruption may have been as little as 4 months away, a large eruption in my opinion was simply improbable. If an eruption did hypothetically occur, it would have been of a small size in the opinion of GeologyHub. Maybe VEI 2-3. Q: If the magmatic intrusion did reach the surface, what do I think would have occurred? A: I would expect a small 150-300 foot high cinder cone to form in a mildly explosive VEI 2-3 eruption, perhaps covering an area of 1-2 km2 in a layer of basaltic lava. This is essentially what occurred 16,000 years ago during Long Valley Caldera’s last eruption. Although I have no direct proof of the intruding magma being basaltic, I made the assumption that it was basaltic based off of the Long Valley Caldera’s last several eruptions (the most recent of which was 16,000 years ago) producing basaltic lava. Some supervolcanoes erupt all the time, and the vast majority of these eruptions are not large. Take for example the Sakurajima volcano which is still erupting right now. It is part of the Aira Caldera supervolcano. Or, also in Japan, the Aso caldera has erupted more than 100 times in the last 500 years. None of these eruptions in the last 500 years were any larger than a VEI of 3. Q: Would you willingly live in the Long Valley Caldera, or in the town of Mammoth Lakes? A: Absolutely. In my opinion, what occurred in the 1980s was highly unusual, unlikely to repeat again in the next 100-200 years. I believe there is a low volcanic hazard, but it is low enough that in my opinion I’d feel safe living there. I’d even ski or hike parts of Mammoth Mountain. In fact, I hiked near the zone of tree kill in 2022. People generally love Mammoth Mountain, especially for winter sports activities like skiing and snowboarding. Q: Will any of the 3 intrusions that this video mentioned suddenly reactivate? A: In my opinion, 2 of the 3 will never reactivate. The only one which night is the 8 km depth intrusion which caused approximately 10 inches of uplift in 10 months in 1980. This marks the resurgent dome of the Long Valley Caldera (volcano), and such uplift events are likely quite frequent. Yet, magma will almost certainly not reach the surface in my opinion from this location for many hundreds, perhaps thousands of years. Instead, future eruptions within Long Valley caldera will likely occur at the edge of the caldera, as this represents a natural weak point. As for calling Long Valley a supervolcano, the U.S. Geological Survey calls this volcano as such at this link: www.usgs.gov/faqs/what-are-some-examples-supervolcanoes You might be wondering how I can say that the eruption hazard was overblown in 1982, while also at the same time stating that an eruption was as little as 4 months away. My response is that while an eruption was potentially months away if the magmatic intrusion continued its upward motion at a point in 1982, this was still months away from requiring any form of an evacuation. In other words, the tabloids jumped too far ahead of the logical time table progression involving the volcanic unrest in 1982. Areas aren’t simply evacuated because there is a magmatic intrusion. Evacuations generally only occur once it gets shallow enough to potentially produce an eruption. For example, the Mount Edgecumbe volcano in Alaska is still producing magmatic uplift due to an intrusion, but it is too deep at the present to cause an eruption, therefor an eruption of Sitka is not currently required (as of as of (September 29th 2023). The same was the case in 1982 at the Long Valley Caldera. If the intrusion had instead hypothetically continued upwards for a few more months, reaching shallower than 2,000 meters depth, then some but not all of the tabloids claims might not have been outlandish. Also, in the hypothetical event an eruption did occur in 1982, it would not have destroyed the town of Mammoth Lakes, as lava flows would have been directed away from the town, towards the east. The uplift center was simply in the wrong location for lava to flow towards Mammoth Lakes during such an event. As a final note, I will admit that the prospect of Long Valley producing an 8 km->4 km magmatic intrusion was quite strange and presents a potential problem for an assertion I made in today’s video. Typically, a portion of a magma chamber needs to be >=35% melt for a volcano to even be theoretically capable of producing an eruption. For context, the Long Valley Caldera maximizes out at 27% melt [Source G]. So, an eruption shouldn’t have even been possible to the first place. Therefor, one of the following things must be true: A: We have underestimated the maximum melt percentage in Long Valley’s underlying magma chamber. B: It is possible that a maximum melt % does not prevent a magmatic intrusion from occurring. Instead, it might simply prevent a magmatic intrusion if one does occur from erupting due to some mechanism which is not yet understood. In other words, the 1981-1982 magmatic intrusion may have been doomed to fail from day 1. C: We might be incorrectly assuming the minimum melt % a portion of a magma body must reach for an eruption to be theoretically possible. Perhaps the value is lower than 35%? Yes, this comment is actually longer than the words I said in today’s video. But hey, I had a lot to say! [Source G] Ashton F. Flinders, David R. Shelly, Philip B. Dawson, David P. Hill, Barbara Tripoli, Yang Shen; Seismic evidence for significant melt beneath the Long Valley Caldera, California, USA. Geology 2018;; 46 (9): 799-802. doi: doi.org/10.1130/G45094.1

Its amazing how far our understanding of volcanology has changed in the last 40 years.

Id's say everyone was a little jumpy in 1980s after St Helens massive eruption. Great video

I was living in Bakersfield in the 1980s. I remember all those earthquakes from Mammoth Lake/Long Valley. That is when I officially lost track of all the earthquakes I had experienced! It was like, “Every time Mammoth Lakes quakes, Bakersfield always shakes.”

As an East Coast transplant to California, the geology here is certainly not something I'm used to. I love Mammoth and it's very interesting to hear about the history of volcanic and seismic activity in the area. This is such a funny and interesting story.

Thanks, Geology Hub! This event is a great reminder that most magmatic intrusions fail and never see the light of day. We all know this, but large caldera systems (commonly called supervolcanoes) do not always erupt in VEI 7, 8 or possibly even 9 eruptions. The Mono Inyo craters has one particular eruption that seems to be related to one of the 535-536 mystery eruptions, via cryptotephras... Aleral Wei's Wikipedia edits brought this 5o my mind. Sorry for this, but I misspelled "Thanks" as "Thanos"!

1:25 this shot of Twin Lakes brings back so many good memories

I lived near Lassen and used to swim in hot creeks- one day swimming there was a rumbler quake and we ran out of the creek. A few minutes later boiling water came flowing down the creek...

Was in Mammoth while this was happening (1982) - I vividly remember the earthquakes and seeing all the trees flex. Quite an experiance. Used to camp all the time in the early 80s at Horseshoe Lake - pretty much right where the die off is. Definitely created in interest in all things geologic for me.

i was there at Rock Creek with my parents when the earthquakes happened. Much running out of buildings, getting covered with snow falling from trees etc.

How did I never notice that the Mono Lake islands were lined up with Mammoth? I've spent a lot of time there and it's awesome. Good info!

Thanks for your interesting and informative videos!

I remember this. The memory of St Helens was still fresh, and people were ripe for a scare. Shame on the tabloid media!

Awesome content/awesome channel. Keep up the good work!!

I don't understand people. in terms of volcano activities, imminent doesn't mean it will happen. an eruption is the end result of several chains of events. if the volcano stalled at the last moment for whatever reason, then no matter how ready the volcano is, there's no eruption. there is a need to be vigilant and be prepared. panicking is not the proper action.

thanks for the information interesting fact in the early 80s a road named the 'mammoth escape route' was built but local businesses and land owners complained so it was renamed the 'mammoth scenic loop'

I've seen your videos on the Azores, but would you please do a video covering the 1957-1958 eruption of Capelinhos on Faial specifically?

Long valley caldera is underrated

Mammoth Mountain looks to me like it had a lateral eruption sort of like Mt. St. Helens sometime in the past.

Thank you for sharing. After Mt St Helen erupted back in the 1980's. When the USGS gives a warning it us good to pay attention and stay praying. God bless

One of the vents is like literally in middle of the slopes and they just casually say to avoid it sure I can but not everyone there is a good skiier, some dont have brains that function through the weed, and whiteouts sometimes make traversing around very confusing.

It is vital that this channel continues its vigilance regarding continental volcanics; we all sense something is going to happen soon but a little Science helps allay the anxiety that percolates just beneath the social awareness managed by social media.

I remember this. It was used, in part, in the movie "Dante's Peak"...

I have 2 questions. 1st, the recent Swarm of activity off the coast of Western Portugal, near the Azores. Is this , now we've moved into the 5.0 magnitude, of concern and is this tectonic or volcanic in origin? I also wonder about the recent activity off vancouver Island in Western Canada, mid 4.pointers and then off the coast of northern California, on what appears to be the same fault line.. is this pressure releasing or something building up? . I absolutely love your channel, I'm learning so much . I check The volcano discovery app about 5 times a day, and my main regret in life is not being a Geologist.

Some of my favorite hot springs ♨️ are in that area!

Wasn't this referenced in the movie Dante's Peak?

I love the Eastern Sierra!

Thanks.

@GeologyHub like @sifarren asked about in their 2nd question are the quakes in Vancouver island and off the coast (since they appear to be on the same fault) releasing pressure or is something building up? be honest

I am watching this video in Mammoth Lakes, CA. The geology here is awesome.

I was in Mammoth when the two 6 earthquakes hit.

Great List of volcanoes yet to cover: - Semeru - Aconcagua (Extinct) - Trindade (maybe extinct) - Agung - Pico do Fogo

I didn’t know they had a volcano

When was the last time Yellowstone was (hypothetically) close to erupting?

better to be safe than gone! As this along the ring of fire on the west side of the NA continent.

Caltech said once magma runs under the Salton sea and under Santa Monica mountains

holy crap i just moved here

Not first.

Come on Mammoth Lakes Mountain, quit with the forplay...

Hot Creek, south of MammothLakes got hotter

Supervolcano

So the movie Volcano was almost real🤯

JEEEEZIZ! your voice is just HORENDOUS! PLEASE find someone-else to narrate your videos. (they are great!)

If your an observant person there will be a major eruption on the west coast of the US, but there are a lot of devasting things that will happen before then

Yeah that was due to my husband and my honeymoon 🥰🔥

So in effect, some magma moved, the mountain farted and people lost their sh#t...

"While trees need carbon dioxide to grow too much is lethal to them". Words that global warming deniers may want to pay attention to.

"While trees need carbon dioxide to survive, too much is lethal to them." Thanks for pointing this out. There are still people repeating the myth that "it's fine to release carbon dioxide into the atmosphere because the plants will just absorb it." Carbon dioxide to plants is like oxygen to humans. We can't live without it, but there's a certain percentage by which we can no longer safely inhale it.

Who was sacrificed to appease the gods?

Nothing of value would’ve been lost