# Can vulcanic caves have stalagmites and stalagtites? **URL:** \ **Category:** Factual Questions\ **Created:** [February 15, 2024, 8:55pm UTC](https://boards.straightdope.com/t/can-vulcanic-caves-have-stalagmites-and-stalagtites/997621 "2024-02-15T20:55:37Z")\ **Posts on this page:** 16\ **Page:** 1
**Author:** ![Pardel-Lux](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/pardel-lux/32/20182_2.png) [@Pardel-Lux](https://boards.straightdope.com/u/Pardel-Lux)\ **Post date:** [February 15, 2024, 8:55pm UTC](https://boards.straightdope.com/t/can-vulcanic-caves-have-stalagmites-and-stalagtites/997621/1 "2024-02-15T20:55:37Z")
Imagine a cave in a vulcano, half way up the summit. Stalagmites and stalagtites form mostly from calcium carbonate, so I wonder whether lava has the ingredients to be dissolved by water to combine with atmospheric CO2 to precipitate as CaCO3. I know that there are many different types of lava, but does it ever include significant amounts of Ca, in other words: if I enter a cave and see stalagmites and stalactites, can I infer that the geological origin of the surroundings is _ **not** _ volcanic? ---
**Author:** ![rbroome](https://avatars.discourse-cdn.com/v4/letter/r/838e76/32.png) [@rbroome](https://boards.straightdope.com/u/rbroome)\ **Post date:** [February 16, 2024, 1:03am UTC](https://boards.straightdope.com/t/can-vulcanic-caves-have-stalagmites-and-stalagtites/997621/2 "2024-02-16T01:03:14Z")
Well I have been in lava tubes in Hawaii that definitely had stalagtites and I think stalagmites. And they definitely weren’t calcium carbonate. 🙂 Molten rock did drip from the ceiling when the tube was formed. They weren’t very big, as I remember them, but definitely spikes that were part of the ceiling. So, no. ---
**Author:** ![Beckdawrek](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/beckdawrek/32/3647_2.png) [@Beckdawrek](https://boards.straightdope.com/u/Beckdawrek)\ **Post date:** [February 16, 2024, 1:20am UTC](https://boards.straightdope.com/t/can-vulcanic-caves-have-stalagmites-and-stalagtites/997621/3 "2024-02-16T01:20:46Z")
Isn’t that Volcanic? Or ask Spock. ---
**Author:** ![Banksiaman](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/banksiaman/32/3334_2.png) [@Banksiaman](https://boards.straightdope.com/u/Banksiaman)\ **Post date:** [February 16, 2024, 4:42am UTC](https://boards.straightdope.com/t/can-vulcanic-caves-have-stalagmites-and-stalagtites/997621/4 "2024-02-16T04:42:16Z")
One thing that would work against them forming is that in normal limestone caves the stalactites and stalagmites form through the dissolving of calcium carbonate, and then evaporation, so they form as residual calcium crud adhering seamlessly to earlier crud. Volcanic materials don’'t dissolve in water - even the finest particles are pieces of vapourised rock or volcanic glass which can definitely be carried along like a sediment but as particles, not solution. Once the water dissolves this will be left, but is not I think going to cement itself together without additional pressure. Our basement garage used to have little stalactites from leaching concrete, but that’s very much a human model of a limestone cave. ---
**Author:** ![purplehorseshoe](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/purplehorseshoe/32/2996_2.png) [@purplehorseshoe](https://boards.straightdope.com/u/purplehorseshoe)\ **Post date:** [February 16, 2024, 5:11am UTC](https://boards.straightdope.com/t/can-vulcanic-caves-have-stalagmites-and-stalagtites/997621/5 "2024-02-16T05:11:53Z")
Do caves naturally form in the sides of volcanoes in the first place? ---
**Author:** ![CairoCarol](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/cairocarol/32/3825_2.png) [@CairoCarol](https://boards.straightdope.com/u/CairoCarol)\ **Post date:** [February 16, 2024, 5:15am UTC](https://boards.straightdope.com/t/can-vulcanic-caves-have-stalagmites-and-stalagtites/997621/6 "2024-02-16T05:15:20Z")
Hell yeah. [Lava tubes](https://www.nps.gov/havo/learn/nature/lava-tubes.htm). Added emphasis mine: > As islands created by volcanoes, Hawaiʻi is criss-crossed by countless lava tubes. These underground passageways, also known as pyroducts, are created by lava flows themselves and are capable of transporting great quantities of lava long distances underneath the surface. When the supply of lava stops at the end of an eruption, or if it gets diverted elsewhere, _ **it leaves behind an empty cave.** _ > > When a lava tube is active, lava travels along its floor at temperatures that exceed 2,000º F (1090º C). Winds of superheated fume may blast through the tunnel, yet the only sound may be the constant soft hiss of the relentless flow. > > Once lava subsides, these subterranean corridors become home to unique ecosystems of troglobites, animals specifically adapted to live in this dark isolated world. Distinct species of crickets and spiders develop alongside special microbial colonies found nowhere else. > > The Kazumura lava tube system, within the 500 year-old ‘Ailā‘au lava flow of Kīlauea, is more than 40 miles (65 km) long and is thought to be the longest lava tube cave in the world. Tubes may be up to several dozen feet wide. ---
**Author:** ![MrDibble](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mrdibble/32/114_2.png) [@MrDibble](https://boards.straightdope.com/u/MrDibble)\ **Post date:** [February 16, 2024, 5:25am UTC](https://boards.straightdope.com/t/can-vulcanic-caves-have-stalagmites-and-stalagtites/997621/7 "2024-02-16T05:25:20Z")
> [@Pardel-Lux](#): > > I know that there are many different types of lava, but does it ever include significant amounts of Ca Definitely yes. > **[Ol Doinyo Lengai](https://en.wikipedia.org/wiki/Ol_Doinyo_Lengai)** > > Ol Doinyo Lengai is an active volcano in northern Tanzania. It consists of a volcanic cone with two craters, the northern of which has erupted during historical time. Uniquely for volcanoes on Earth, it has erupted natrocarbonatite, an unusually low temperature and highly fluid type of magma. Eruptions in 2007–2008 affected the surrounding region. > The Maasai and Sonjo people refer to the volcano as "The Mountain of God", associated with a myth of the abode of the god Engai, who withdrew there af... > **[Carbonatite](https://en.wikipedia.org/wiki/Carbonatite)** > > Carbonatite (/kɑːrˈbɒnəˌtaɪt/) is a type of intrusive or extrusive igneous rock defined by mineralogic composition consisting of greater than 50% carbonate minerals. Carbonatites may be confused with marble and may require geochemical verification. > Carbonatites usually occur as small plugs within zoned alkalic intrusive complexes, or as dikes, sills, breccias, and veins. They are almost exclusively associated with continental rift-related tectonic settings. It seems that there has been a steady ... > [@Pardel-Lux](#): > > if I enter a cave and see stalagmites and stalactites, can I infer that the geological origin of the surroundings is _ **not** _ volcanic? Definitely no: [(from an inactive crater at the above volcano](http://www.photovolcanica.com/VolcanoInfo/Oldoinyo%20Lengai/Lengai2004_1_25.jpg) - sorry, image won’t preview) ([source](http://www.photovolcanica.com/VolcanoInfo/Oldoinyo%20Lengai/Oldoinyo%20Lengai.html)) > [@Banksiaman](#): > > Volcanic materials don’'t dissolve in water Some do. ---
**Author:** ![MrDibble](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mrdibble/32/114_2.png) [@MrDibble](https://boards.straightdope.com/u/MrDibble)\ **Post date:** [February 16, 2024, 5:48am UTC](https://boards.straightdope.com/t/can-vulcanic-caves-have-stalagmites-and-stalagtites/997621/8 "2024-02-16T05:48:14Z")
ETA: Also, even if the lava/volcano doesn’t have carbonate (doesn’t have to be calcium, BTW, can also be magnesium), it can still get carbonate deposited in it from groundwater that has traveled through surrounding carbonate rocks, say if your volcano erupted through limestone. ---
**Author:** ![MrDibble](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mrdibble/32/114_2.png) [@MrDibble](https://boards.straightdope.com/u/MrDibble)\ **Post date:** [February 16, 2024, 5:52am UTC](https://boards.straightdope.com/t/can-vulcanic-caves-have-stalagmites-and-stalagtites/997621/9 "2024-02-16T05:52:20Z")
> [@rbroome](#): > > Well I have been in lava tubes in Hawaii that definitely had stalagtites and I think stalagmites. And they definitely weren’t calcium carbonate. 🙂 Molten rock did drip from the ceiling when the tube was formed. Those are formed by [vapour deposition](https://www.sciencedirect.com/science/article/abs/pii/0024493785900167) [or hydrothermal deposition, not molten lava](https://caves.org/virtualcave/tubular-lava-stalactites/). But yes, they are not carbonates. Note that you _can_ get [molten-rock drip formations](https://en.wikipedia.org/wiki/Stalactite#Shark_tooth_stalactites) as well, but the tubular ones in Hawaiʻi are not it. Even though the Wiki article talks about “lava” in reference to the liquid that forms them, it’s more properly associated superheated water-based hydrothermal fluids, not lava proper, that is the carrier for the deposited minerals. ---
**Author:** ![Pardel-Lux](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/pardel-lux/32/20182_2.png) [@Pardel-Lux](https://boards.straightdope.com/u/Pardel-Lux)\ **Post date:** [February 16, 2024, 9:47am UTC](https://boards.straightdope.com/t/can-vulcanic-caves-have-stalagmites-and-stalagtites/997621/10 "2024-02-16T09:47:30Z")
Thank you for the comprehensive and clear answers, **MrDibble** , that pretty much solves my question. > [@Beckdawrek](#): > > Isn’t that Volcanic? [Vulcanic](https://it.wikipedia.org/wiki/Cenere_vulcanica), [volcanic](https://en.wikipedia.org/wiki/Volcanic_ash), [vulkanisch](https://de.wikipedia.org/wiki/Vulkanische_Asche), it may simply depend on the language Spock spoke. I easily get confused with those vowel shifts, I hope it is not contagious like yawning. ---
**Author:** ![MrDibble](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mrdibble/32/114_2.png) [@MrDibble](https://boards.straightdope.com/u/MrDibble)\ **Post date:** [February 16, 2024, 10:18am UTC](https://boards.straightdope.com/t/can-vulcanic-caves-have-stalagmites-and-stalagtites/997621/11 "2024-02-16T10:18:01Z")
One other thing - you asked whether lava ever includes significant amounts of Ca, but I think it’s worth pointing out a misunderstanding I think you may have - _Lots_ of other minerals have variants that contain significant calcium, including some of the most important silicate minerals that make up the most common lavas: [Plagioclase feldspars](https://en.wikipedia.org/wiki/Plagioclase), [pyroxenes](https://en.wikipedia.org/wiki/Augite) and [amphiboles](https://en.wikipedia.org/wiki/Hornblende). So in a way, almost all lavas contains Ca. But these are silicates, and so the calcium is bound in the rock until the mineralogy is altered, by either weathering or metamorphism. ---
**Author:** ![Pardel-Lux](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/pardel-lux/32/20182_2.png) [@Pardel-Lux](https://boards.straightdope.com/u/Pardel-Lux)\ **Post date:** [February 16, 2024, 10:31am UTC](https://boards.straightdope.com/t/can-vulcanic-caves-have-stalagmites-and-stalagtites/997621/12 "2024-02-16T10:31:52Z")
I knew it would not be easy or simple! Good to know that not everything that contains Ca is a carbonate but that it can turn into one by weathering or metamorphism. That makes a lot of sense. Thanks again! ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [February 17, 2024, 2:16pm UTC](https://boards.straightdope.com/t/can-vulcanic-caves-have-stalagmites-and-stalagtites/997621/13 "2024-02-17T14:16:08Z")
I suppose that, if you get any kind of rock hot enough, it’ll melt. And the molten rock will still have the same composition as the original, as it will when it re-solidifies (though possibly in different compounds, or with a different structure). So it’d have to be possible to have carboniferous igneous rock. ---
**Author:** ![MrDibble](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mrdibble/32/114_2.png) [@MrDibble](https://boards.straightdope.com/u/MrDibble)\ **Post date:** [February 17, 2024, 3:25pm UTC](https://boards.straightdope.com/t/can-vulcanic-caves-have-stalagmites-and-stalagtites/997621/14 "2024-02-17T15:25:23Z")
> [@Chronos](#): > > And the molten rock will still have the same composition as the original, as it will when it re-solidifies Not exactly - stuff can escape as gases. [Especially CO2](https://en.wikipedia.org/wiki/Carbonate%E2%80%93silicate_cycle) > [@Chronos](#): > > So it’d have to be possible to have carboniferous igneous rock. I’ve [already cited](https://en.wikipedia.org/wiki/Carbonatite) where it’s more than possible - BUT carbonatites are shown by isotope analysis to _not_ come from molten sedimentary carbonates, but instead from [partial melting](https://en.wikipedia.org/wiki/Partial_melting) and [fractional crystallization](https://en.wikipedia.org/wiki/Fractional_crystallization_(geology)) of alkaline magmas. When sedimentary carbonates get heated, they release their carbon as CO2 way before they get to melting temperatures. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [February 17, 2024, 3:49pm UTC](https://boards.straightdope.com/t/can-vulcanic-caves-have-stalagmites-and-stalagtites/997621/15 "2024-02-17T15:49:32Z")
> [@MrDibble](#): > > Not exactly - stuff can escape as gases. [Especially CO2](https://en.wikipedia.org/wiki/Carbonate%E2%80%93silicate_cycle) Ah. That had occurred to me, but I rejected it on the grounds that this could all be happening far from atmospheric oxygen. I’d forgotten that the rocks themselves would contain oxygen, too. ---
**Author:** ![blondebear](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/blondebear/32/1022_2.png) [@blondebear](https://boards.straightdope.com/u/blondebear)\ **Post date:** [February 17, 2024, 6:14pm UTC](https://boards.straightdope.com/t/can-vulcanic-caves-have-stalagmites-and-stalagtites/997621/16 "2024-02-17T18:14:26Z")
If you’re ever in Bend Oregon, I recommend a visit to Lava River Cave (don’t forget your flashlights!) From the Forest Service website [A Journey Through Lava River Cave](https://www.fs.usda.gov/detailfull/deschutes/specialplaces/?cid=fseprd1004688&width=full) _In other areas of the tube volcanic stalactites occur. These “lavacicles” are found in two forms: hollow cylindrically shaped “straws,” formed by escaping gases, and the cone-shaped drip pendants, formed by remelted lava dripping from ceilings and walls._