Talk:Caldera

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Terminology

The term "Caldera" was introduced in to the geological vocabulary as a result of Leopold von Buch's visit to the Canary Islands in particular Tenerife and then La Palma. In fact his journal distinguishes between the Las Canadas Caldera and the Caldera de Taburiente as follows "... The area we were in looked as if it had been created by the outpouring of rocks from the very bowels of the Earth. I asked my guides what name this place had and they told me that it was named "El Caldera de las Canadas." I noted that a large volcano which the guides called El Teide, stood guard over the caldera and that also there were cliffs that were almost vertical. As we ventured further into the caldera I decided that this area had not only been born from the bowels of the Earth, but it also must have at some time in the past descended into those same bowels. Later when we were eating one of my guides gave me a local broth in a bowl and informed me that the broth was made from chickens, but that it was in a "caldera" the very bowl my broth was in. From this I deduced that the Spanish term for a bowl was in fact "Caldera," and realised why the local name for the great depression we had visited was also called a caldera. Later when I visited La Palma I was taken by my guides to visit a great depression which we entered via a narrow gorge. Suddenly the vista changed and I was looking at an immense depression, with cliffs which attained a height greater than those I had seen at the Las Canadas. It was obvious though that whilst they were both caldera's, the caldera on Tenerife had been created in a different manner to that on La Palma. I consider the caldera on Tenerife to be formed by the activity of the volcano, but a different process has caused the caldera de Taburiente which is the name the local citizens call it..."The Geologist (talk) 17:11, 10 April 2012 (UTC)

Late addition - while von Buch was the first to extensively discuss the Caldera de Taburiente on La Palma, naturalists before him (they wouldn't have called themselves "geologist" at the time yet) wrote about it descriptively in geological context already. These include John Payne in 1796 ("Geographical extracts, forming a general view of earth and nature", chapter "Volcanoes", p. 227), Alexander von Humboldt (diaries 1799-1805). The Caldera de Taburiente is already mentioned under that name in 1776 by José de Viera y Clavijo in the "Noticias de la historia general de las islas de Canaria" (Volume 3, pp. 498), who describes it as famous. Juan de Abreu de Galindo in 1767 in his "The History of the Discovery and Conquest of the Canary Islands" (p. 103-104) was clearly copied by Payne later (same wording, almost exactly), and describes the Caldera as well, under it's local name. I think it's still valid to leave it as is, since von Buch was the first to extensively (and correctly) geologically discuss it. --Carboxen~enwiki (talk) 01:38, 9 September 2015 (UTC)

Carboxen, Thanks for the updated information. I agree that whilst its usage pre-dates von Buch, the term as used in geology and volcanology did not exist. It was only after von Buch published his memoirs that the term entered the geological vocabulary. Thanks again for the information.The Geologist (talk) 18:43, 16 September 2015 (UTC)

Split

Should probably be split into two or more pages. There were at least two companies by the name of Caldera (Caldera Systems, Inc., and something else) at the same time for a while. —Mulad

Since this is a geology / volcanolgy page it is the companies that are at fault. The Geologist (talk) 16:27, 1 May 2008 (UTC)

Confusion

207.118.9.58 01:25, 7 November 2006 (UTC)I was under the impression that the term caldera referred to a specific type of magma chamber that tends to create these depressions, not the depressions themselves. The article seems to partially agree with me. Yellowstone, for example, shows no such depression due to the fact that the magma chamber has exceeded "half full" (when compared to evidence of previous Yellowstone eruptions). The only places where one can claim to see such a depression are a series of cliffs formed by several eruptions over eons, and are not a sign of any true land depression.

A caldera is the depression formed when the edifice collapses INTO the empty magma chamber and the cliffs - surprise, surprise!, represent the eroded ring fracture.The Geologist (talk) 16:25, 1 May 2008 (UTC)

1980?

After the article says 'When Mount St. Helens erupted' .. there should be a date. But are they talking about the 1980 eruption?

207.118.9.58 01:20, 7 November 2006 (UTC)Yes, they are speaking of the 1980 eruption.

volcanic edifice

I do not understand at all what a volcanic edifice is.. Please explain...

Edifice means "Structure" from the latin "Edifico" which means "I build." Hence "Volcanic edifice" is the volcanic structure. The Geologist (talk) 16:28, 1 May 2008 (UTC)

An edifice is a massive or imposing building/structure/natural-formation, usually rising vertically (or near vertical) up out of something. Chaosdruid (talk) 21:08, 4 January 2015 (UTC)

As this is a geology page it refers to volcanic structures. Even a small house is an "edifice" but has nothing to do with a volcano.

ALL of North America?

The Wikipedia article on the Yellowstone caldera states that ash from the volcano's eruption 640,000 years ago covered MOST of North America. Even that sounds a little hyperbolic. Does this include both Alaska and Yucatan? I have changed ALL to MOST in keeping with the other Wikipedia article. Perhaps "a major portion" would be even better. 76.123.203.164 (talk) 12:48, 25 March 2008 (UTC)

I agree. This USGS page says that "Huge volumes of volcanic ash were blasted high into the atmosphere, and deposits of this ash can still be found in places as distant from Yellowstone as Iowa, Louisiana, and California"; not all of North America by any means.

multiplicity

Is it calderas or caldera for the proper plural form of this phenomenon? Sochwa (talk) 03:17, 30 March 2008 (UTC)

"Calderas" is used when more than one caldera is being discussed as in "Nested calderas"The Geologist (talk) 16:23, 1 May 2008 (UTC)

correct wording?

"Yellowstone caldera ... erupted"? Is the caldera not the indirect result of an eruption? Or was there a caldera before, that re-erupted? 71.233.0.99 (talk) 00:58, 4 January 2009 (UTC)

Before the last caldera forming eruption about 640,000 years ago, there were at least 6 earlier caldera forming explosive eruptions. The USGS has full details of the eruptions.The Geologist (talk) 15:20, 22 January 2013 (UTC)

date of santorini

The image states that santorini happened in 3615 BP most people have no clue what the hell is that. I request that the date be changed to the CE calendar or at least a note stating that date. —Preceding unsigned comment added by Nemo1986 (talk • contribs) 15:35, 21 March 2009 (UTC)

The 'BP' was linked, so people should have some clue I would hope. If you look at the Santorini page you will see a range of ages depending on whether you use archeological or radiocarbon dating. The discrepancy between these two shows no sign of disappearing. That aside I will put '1600 BCE' in brackets after the date on the Caldera page ( I know that 1600 + 2009 does not = 3615, but we are talking approximate here), unless you feel like being bold and beating me to it. Mikenorton (talk) 15:54, 21 March 2009 (UTC)

The term "BP" is a recognised scientific term and is used to indicate earlier dates of events that have occurred within human history but are of unprovable date. Also used in some scientific works is the term "BCE" and "CE" meaning "Before the Common Era" and "Common Era" and are in fact related to the religious term "BC" and "AD".

In respect to the Santorini eruption. Many authors have published papers stating that radiometric dating indicates that this occurred in 1615 BC/BP/BCE but this date is strongly debated by arcgaeologists. There ia also some claims that the eruption occurred in the October of that year and is based upon field evidence of a lone olive tree which was buried in the ash and pumice. The Geologist (talk) 16:07, 8 August 2010 (UTC)

Timeline Picture

Caldera Timeline Picture is necessary. People deepen the scientific understanding to the caldera by the picture. --AvengerX (talk) 16:59, 4 January 2010 (UTC)

Timeline of what? --Guanlong wucaii 16:25, 15 February 2010 (UTC)

So What is a Caldera?

The article opens with: "A caldera is a cauldron-like volcanic feature usually formed by the collapse of land following a volcanic eruption. They are sometimes confused with volcanic craters." Neither here nor anywhere else is it explained precisely what a caldera actually is, nor how it differs from a volcanic crater. If they are sometimes confused, then all the more reason to clear up this potential misconception. The images provided are no help in any of this, as they do not label either the caldera or the crater. Whatthefat (talk) 18:15, 27 June 2012 (UTC)

A caldera forms as a result of volcanic action, when parts collapse forming a bowl cauldron or caldera, whereas a crater forms as an opening prior to or during an eruption. Calderas can form during an eruption as well as afterwards.The Geologist (talk) 17:56, 25 November 2012 (UTC)

grossly simplified - caldera is a collapsed dome while crater is one where the dome has been blown away. Caldera formation is instant but craters can form instantly or through prolonged activity. Richiez (talk) 23:45, 28 December 2012 (UTC)

No caldera formation can be and usually is instantaneous, BUT as always exceptions do occur. It is not formed where a "dome has been blown away", but forms when the magma in the chamber has not been replaced in sufficient volume to support the volcano above, so that the whole lot collapses downwards. Craters usually form almost instantaneously too, but the cones and domes form over a period of time. Incidentally during the 2007 eruption at the Piton de la Fournaise the material in the main crater slid downwards by about 700 metres deepening the caldera. The Geologist (talk) 17:34, 10 January 2013 (UTC)

A caldera is a surface depression resulting from a magma-chamber roof collapse. Any old arbitrarily large crater is not a caldera (and I've been having minor trouble in that regard). And, as we have seen recently at Kilauea (2018), the collapse doesn't have to be "instant", but can progress in stages. :2601:444:300:EA10:24A7:DBA4:7903:4B50 (talk) 07:31, 14 November 2021 (UTC)

References

Misleading titles, more generic pic needed

Hi

The picture of the progression of the caldera, while great in itself as a depiction of Mount Mazama, does not adequately describe a caldera and has misleading titling.

• The second frame seems to be showing us a "Caldera Collapse".
• There is nothing to explain the island/water etc. in the fourth frame.

1. Obviously the caldera cannot be collapsing, as it is what remains "after" the collapse. Perhaps retitling it as "Caldera Formation" might work?
2. I would suggest removing the last frame, as it is specific and not all will have lakes or islands, and replacing it with either a generic cross-section or just adding text to explain that the resulting crater will fill in over time and may form a lake. The text could say something like "... continuing volcanic activity at these sites can lead to new domes growing within the caldera, forming islands within the caldera lake."

Thinking about it a little more, perhaps even simply adding some infill to frame 3? Chaosdruid (talk) 21:00, 4 January 2015 (UTC)

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Mount Tehema

I reverted an addition of Mount Tehema, California, to the list of North American calderas. I can find no Mount Tehema in Google Maps. There is a Mount Tehama, but the Wikipedia article identifies it as an eroded stratovolcano, not a caldera. I am explaining the reversion here on the off chance there really is a notable Mount Tehema that is a caldera, for which a source can be produced; or in case Mount Tehema is incorrectly identified as a stratovolcano at Wikipedia itself. Otherwise, Mount Tehema should not be in the list. --Kent G. Budge (talk) 05:04, 18 August 2019 (UTC)

Thanks for noticing this. Caldera is very problematic term because, for example. it is often used incorrectly for any volcanic crater. My understanding of the Lassen Volcanic Centre is that an early stratovolcano (Rockland Volcano) ended its activity with the formation of a collapse caldera (due to magma chamber collapse after an explosive eruption). This caldera was then filled by another stratovolcano, Brokeoff Volcano (also known as Tehama Volcano). Williams (1932) suggested that Brokeoff/Tehama Volcano ended its activity with a collapse caldera, but this is now disputed and recent studies suggest that the Brokeoff/Tehama "caldera" is probably an erosional feature, making Brokeoff/Tehama Volcano an eroded stratovolcano, not a (collapse) caldera. GeoWriter (talk) 11:56, 18 August 2019 (UTC)

@GeoWriter: I thought the consensus has long been that Tehama is an erosional caldera, that is, demolished by erosion rather than eruption. The question is whether "caldera" should be extended to cover this "erosional caldera" type. The consensus seems to be to consider Tehama that, but I know of no other feature termed an "erosional caldera". Jasper Deng (talk) 13:02, 18 August 2019 (UTC)

I agree that Tehama has been/could be described as an erosional caldera. In my previous comment, I should probably have written "not a collapse caldera" instead of "not a (collapse) caldera". I think both types, collapse and erosional, are widely accepted by geologists as calderas. GeoWriter (talk) 13:54, 18 August 2019 (UTC)

Are Mount Pinatubo and Tambora's Calderas actually Calderas?

An IP User has said that Mount Tambora's and Mount Pinatubo's calderas are actually explosion craters. I was going to revert his undoing of my revision but I wanted to avoid an edit war, so wee need to discuss.-The Space Enthusiast (talk) 08:35, 14 November 2021 (UTC)

No, they are not. Neither of the famous Tambora or Pinatubo eruptions evince geologic indication of magma chamber roof collapses. What they do show is mountain-decapitation. Plinian eruptions can literally blow the tops off stratovolcano rubblepiles (or landslide or heave them out of the way, as seen at Mount St. Helens in 1980 and Anak Krakatoa in 2018) to leave impressive-sized craters without caldera-formation being present. By contrast, caldera-formation does not require a violent eruption at all, only structural failure of the roof of the magma chamber. --2601:444:300:EA10:5423:78DA:FDF9:47C7 (talk) 10:02, 14 November 2021 (UTC)

Kilauea caldera formation (non-explosive): https://www.youtube.com/watch?v=mIK6l5vNT8o

Okay, but there is more consensus on those actually being calderas. Also, please provide a source.--The Space Enthusiast (talk) 11:35, 14 November 2021 (UTC)

This NASA site describes Tambora as a caldera, but the text is ambiguous on whether it actually formed by collapse into a magma chamber. I don't know how reliable this site is, but it describes a caldera-type collapse. This reliable source clearly describes a caldera collapse. This reliable source likewise identifies Pinatubo as a caldera, as does this one. Have you sources that claim these are explosion craters? If so, there's a scientific controversy about their nature that is worth noting. Otherwise, we accept them as calderas. --Kent G. Budge (talk) 16:19, 14 November 2021 (UTC)

Pinatubo: Reliable sources describe the crater formed in the 1991 eruption of Pinatubo as a caldera, which was formed by withdrawal of magma from a magma chamber (and collapse of the unsupported crater floor/magma chamber roof). At Pinatubo, the amount of collapse was measured while it was happening. Also, at Pinatubo there are known outward dipping ring faults, along which movement occurred to facilate the collapse. Nothing to do with mountain summit removal by explosion. In the most authoritative book about volcanoes (Sigurdsson, H. et al (editors) (2015) "Encyclopedia of Volcanoes", 2nd edition) the chapter on calderas uses Pinatubo as an example of a caldera (in the correct strict sense of being formed by collapse). The primary book about the 1991 eruption of Pinatubo ("Fire and Mud" by PHILVOLCS and USGS) gives details of the caldera formation by collapse, including measurements of crater floor subsidence. Other sources describing Pinatubo's collapse caldera include: USGS (2016) "Remembering Mount Pinatubo 25 Years Ago: Mitigating a Crisis".

Tambora: Sources which describe Tambora's crater collapse to form a collapse caldera include (1) Oppenheimer, C. (2003) "Climatic, environmental and human consequences of the largest known historic eruption: Tambora volcano (Indonesia) 1815", Progress in Physical Geography, volume 27, pages 230–259 and (2) Sutawidjaja, I.S.; Sigurdsson, H.; Abrams, L. (2006) "Characterization of volcanic deposits and geoarchaeological studies from the 1815 eruption of Tambora volcano", Jurnal Geologi Indonesia, volume 1, pages 49-57.

It is frustrating that some large craters are wrongly described as calderas when they are actually not formed by collapse, but Pinatubo and Tambora are not in that category of craters without crater floor collapse.

I suggest that Pinatubo and Tambora could be reinstated into this Wikipedia article (with at least some of the useful additional sources that this discussion has revealed). — GeoWriter (talk) 23:15, 14 November 2021 (UTC)

I freely stipulate that ostensibly reliable sources can be found, but venture that much of these are passing mentions in for-public-consumption "anniversary articles" rather than rigorously detailed geologic analysis. The topography around Pinatubo and Tambora do not display ring-shaped fracturing or dropped-block faulting associated with magma chamber roof collapses (especially as most spectacularly seen in Hawaii, which might be the only such event on film). In particular, the cones of each respective mountain are intact, and have not themselves subsided. This strongly suggests that, rather than being true calderas, that their enormous craters were the result of powerful Plinian jetting boring out of the center of the piles, with loose material then tumbling into the emptied hole as the eruption concludes. This should not be mistaken for true fault-block subsidence, as is depicted in the illustrations accompanying the article.--2601:444:300:EA10:74B9:390A:3071:8B16 (talk) 03:26, 17 November 2021 (UTC)

Okay, but I believe we must go with the consensus. Ok, but please, provide a source. If there is, I will read it and be convinced.--The Space Enthusiast (talk) 04:55, 17 November 2021 (UTC)

Also, you seemed to have ignored the fact that there are well known ring faults on Pinatubo.

The Space Enthusiast (talk) 06:38, 21 June 2022 (UTC)

I have also found a source which says that the rapid change of eruptive style at 10 pm on April 10, 1815 from eruption columns to pyroclastic flows happened because of a caldera collapse. The Space Enthusiast (talk) 02:18, 26 June 2022 (UTC)