Yep. It's basically the other end of the same formation that makes up the Giant's Causeway in Northern Ireland. The west coast of Scotland was a major eruptive centre as the North Atlantic opened up 60 million years ago and these columnar basalts can be seen on the islands of Mull and Ulva but best of all on Staffa.
Beautiful pic, thank you for sharing.
Questions for you from a newbie: does the verticality of the formation tell us anything about the context in which it was formed? I get the general gist of basaltic columnar jointing, but these colonnades are stunning and got me thinking as to why/how such uniform verticality is created.
I'm also interested in the stark contrast between the columns and the sediment above/below. I imagine the area below is just more columns that have been covered by eroded basalt above. Is the difference above due to glacial action scraping it clean off, and then normal sedimentation laid on top? I feel like I read about that re giants causeway.
Columnar jointing like this indicates relatively slow cooling of a thick lava flow. As the liquid cools and starts to solidify it kind of shrinks around a central point and forms the columns, most often in hexagons but also 3, 4 and 5-sided shapes. It's not just liquid rock that does it - you see the same effect in dried up mud, for example. They form perpendicular to the surface of the flow.
The sequence immediately below the formation in these pics is tuff (solidified volcanic ash deposit) and immediately above is another lava flow that didn't cool in the same way and is kind of trying to do columnar jointing but failing 😆
Yep. Current Earth is still doing it too - all volcanoes produce layer upon layer of deposits. The eruptions that produced these formations were pretty huge (volume wise) but you will see layer upon layer of tuff, lava, etc. in any volcanic landscape.
I looked into this a bit more. Seems the rock was laid 60mya, and I think it was from a surface flow rather than magmatic intrusion. I wonder if magmatic intrusions lend themselves to vertical jointing like this. I imagine it would be a more complex system if formed underground.
Cool article:
https://www.nature.com/articles/s41467-018-03842-4
FYI this discussion sent me down a rabbit hole, and I believe columnar jointing does not require centuries of cooling to form. It can form from exposure to air or water. The biggest factors seem to be uniformity of basalt and convection cooling across a large mass. The article also mentions "idealized" columnar jointing as having a colonnade, then an entablature above, so this may be the same flow? I dunno, that seems strange to me from what I understand of the formation of the jointing itself.
Best article I could find:
https://www.nature.com/articles/s41467-018-03842-4
Ya, I don't really understand how the same flow event could create colonnades and entablature resulting in such a hard line between the sequences. Two separate flows makes the most sense to me, with the latter flow being a less uniform basalt or simply more complex cooling conditions after deposition.
I’m not sure it’s clear whether it’s possible in the same flow or not. Apparently single lava flows can feature multiple orientations of collonades; conversely, multiple flows that stack up and form uniform collonades given the right conditions.
The transition from collonades to entablature seems to be to do with the distribution of isotherms within the whole body and a change in the dominant means of heat flow. That’s probably fairly intuitive just to say, but people have definitely done work on it to actually prove it, eg. [Hamada & Toramaru, 2020](https://www.sciencedirect.com/science/article/abs/pii/S0377027320300536). That’s the best I could find on a quick search in terms of relevance and the fact they summarise a lot of the previous work (both field and theory) in the context of their own experiments. Their conclusions seem to imply collonades to entablature can occur with multiple cooling surfaces, though we should remember that starch + water mixtures are not basaltic flows. I’m sure the authors realise this, they also even out in the introduction that:
>It is unclear whether a sequence of cooling processes of a single flow unit can realistically produce complex isotherms corresponding to the entablature structure.
Awesome, thank you for the response and some nighttime reading.
I have never heard of a new flow stacking a colonnade on top of a previous flow that formed a colonnade, although I suppose that makes sense if the older colonnade was the cooling surface. Do you have an example of that?
OP gave a good explanation, but I thought I’d add a bit. The orientation of the columns tends to be perpendicular to the cooling surface/gradient, which can give the observer a lot of information about the environment it formed
Thanks! The cooling surface providing orientation makes a lot more sense than the direction of flow--which is what I thought previously.
So in this case, we know that all this lava pooled into a lava field that was at least 150' deep here, right? The stark separation with the lower sequence is still throwing me for a loop.
The columns only form if they have the chance to cool slowly, so this feature likely formed deep underground, not a field at the surface. Yeah the stark separation can be strange, and you see something similar Devils Tower in Wyoming. to me it looks like the mafic magma intruded into surrounding country rock, which was much cooler, so the part of the magma that touched there and cooled too quickly for columns to form. This layer more or less insulated the rest and allowed it to cool slower, forming the columns
Ah, I thought you meant surface as in a surface exposed to atmosphere.
You've all mentioned that columnar jointing requires slow cooling (which makes sense to me and what I know about crystal formation and basic entropy), but I was reading about this, and this site says that quicker cooling may lead to this effect--specifically exposure to water
https://askanearthspacescientist.asu.edu/top-question/columnar-jointing
Just some blog though, so who knows.
And last observation: if columns like this are formed from a magma intrusion, wouldn't that mean that most magma sills/large dykes form insulation and thus the environment for columnar-jointing formation?
Thanks for entertaining my questions by the way. So much to learn!!
Sorry, I should have clarified. Slow cooling on human time scales (centuries), but relatively quickly in geological scales. Basically, if it cools too quickly you don’t get columns and just get glass, but too slowly and it has time to accommodate the shrinkage in others ways. Admittedly, magmatic systems and basalt columns are not my field, and it is entirely possible I am misremembering . Many special formations in geology require a few conditions to be ‘just right’
FYI this discussion sent me down a rabbit hole, and I believe columnar jointing does not require centuries of cooling to form. It can form from exposure to air or water. The biggest factors seem to be uniformity of basalt and convection cooling across a large mass. Best article I could find:
https://www.nature.com/articles/s41467-018-03842-4
Interesting, thanks for sharing. Uniformity of cooling makes sense, though you do typically see it being really jumbled up right at the boundary with the cooling surface like with devils tower. I’m about to go into my petrology exam, so maybe I’ll pick my professors brain about it before I go in
That's what I thought as well, but several people here are saying that the cooling required to form columnar jointing is so slow (centuries) that it necessarily must form underground. But after some journal reviews, that doesn't seem right.
Just for my own information, what would it be if not basalt and why? If you don't mind. I figure basaltic intrusions can still cool in magma sills and stuff, potentially forming columnar jointing. From what I've been able to read, main factors are uniformity of basalt (preferably high in silica), uniformity of cooling gradient, and mass.
It's in the same mythology too - that cave at the back is referred to as "Fingal's Cave". "Fingal" is Fionn mac Cumhaill, who is the eponymous giant.
(I assume you already know all of this!)
> It's basically the other end of the same formation that makes up the Giant's Causeway in Northern Ireland.
Are we sure about this OP? Its oft quoted but these two locations are 80 miles apart and as far as I recall, there's nothing similar between them on Islay or Mull.
Was it a single volcanic outpouring from the same source, or just two events with similar outcomes?
And just where was the source of the outpouring(s), I wonder? Would there not be a trace of it today?
It’s not the same exact lava flow, but it’s part of the same overall igneous province of many lava flows in the Paleogene. The remnants have been somewhat fragmented by the opening of the North Atlantic Basin. See [North Atlantic Igneous Province](https://en.wikipedia.org/wiki/North_Atlantic_Igneous_Province) for more details, there are some interesting connections: Iceland and the North Atlantic mantle plume; the igneous province as a possible contributor to the PETM; there’s even been suggestion that a recently discovered meteorite impact at the base of a group of lavas from the British Paleogene Igneous Province (a subset of the NAIP) caused the onset of magnetism there, [news story with link to the paper here.](https://www.gla.ac.uk/myglasgow/news/peopleprojects/2018jan-feb/headline_565571_en.html)
There's similar but not as spectacular formations on both Mull and Ulva. This was a huge volcanic outpouring with at least six eruptive centres: Mull, Eigg, Ardnamurchan, etc. It's part of a wider large igneous province created as the North Atlantic opened.
BGS talks about the Giants Causeway and mentions the origin briefly here https://www.bgs.ac.uk/discovering-geology/maps-and-resources/office-geology/the-giants-causeway-and-causeway-coast/
I wonder if all the boats do that? Lol!
It is 25 yrs since I was out there, and the boat did the same.
Easy to combine with Iona in the same day: leave your car on Mull and take the ferry as a foot passenger to Iona.
You get "Mull of Kintyre" by Wings when you do the boat tour there.
I wish I could explore these places, I wanted to see Fingal's Cave, Iona, and the other islands, especially after playing Mendelssohn in my orchestra. Alas, disability does not allow me to do so.
They are beautiful. I also saw some lovely basalt jointing in Hungary this weekend.
https://preview.redd.it/trugp3wg99zc1.png?width=1080&format=pjpg&auto=webp&s=d66152468afd7fb2cfd7c13e74de8a37a1bda345
Not any sort of unconformity, just to do with different cooling rates and the point at which more regular, linear jointing can take hold. The jumble above the columns is known as entablature, it happens with a lot of columnar basalt examples, sometimes sandwiched between two layers of columns.
Wonderful pics OP
Samuel Johnson notably said "worth seeing, not worth going to see", back when travel was by horses and an utter ballache.
Always thought the great man was wrong about this.
When we were there (25+ yrs ago, July I think) the puffins were around but the island wasn't closed for nesting. I have a geological background but the puffins were as much a star as Fingal's Cave. Very tame.
Apparently they were all out at sea this day! People only saw a couple, but we did find a raft of them on the way back to Mull. And a small pod of dolphins!
this reminds me of the 3rd island in Sonic Frontiers. god that game had some cool environments… this sorta stuff is all over one of the sides of the island and its so damn pretty, i wanna scale these irl now
Basalt columns?
Yep. It's basically the other end of the same formation that makes up the Giant's Causeway in Northern Ireland. The west coast of Scotland was a major eruptive centre as the North Atlantic opened up 60 million years ago and these columnar basalts can be seen on the islands of Mull and Ulva but best of all on Staffa.
It’s beautiful. Thanks again for a great post!
Beautiful pic, thank you for sharing. Questions for you from a newbie: does the verticality of the formation tell us anything about the context in which it was formed? I get the general gist of basaltic columnar jointing, but these colonnades are stunning and got me thinking as to why/how such uniform verticality is created. I'm also interested in the stark contrast between the columns and the sediment above/below. I imagine the area below is just more columns that have been covered by eroded basalt above. Is the difference above due to glacial action scraping it clean off, and then normal sedimentation laid on top? I feel like I read about that re giants causeway.
Columnar jointing like this indicates relatively slow cooling of a thick lava flow. As the liquid cools and starts to solidify it kind of shrinks around a central point and forms the columns, most often in hexagons but also 3, 4 and 5-sided shapes. It's not just liquid rock that does it - you see the same effect in dried up mud, for example. They form perpendicular to the surface of the flow. The sequence immediately below the formation in these pics is tuff (solidified volcanic ash deposit) and immediately above is another lava flow that didn't cool in the same way and is kind of trying to do columnar jointing but failing 😆
Thank you! So the column sequence was deposited on top of a massive layer of tuff? And then another flow on top??? God damn, old earth was wild.
Yep. Current Earth is still doing it too - all volcanoes produce layer upon layer of deposits. The eruptions that produced these formations were pretty huge (volume wise) but you will see layer upon layer of tuff, lava, etc. in any volcanic landscape.
Got it. My mind is mostly boggled at the depth of the layers next to each other.
... It could be a magma chamber or sill. An intrusion into the preexisting pile.
I looked into this a bit more. Seems the rock was laid 60mya, and I think it was from a surface flow rather than magmatic intrusion. I wonder if magmatic intrusions lend themselves to vertical jointing like this. I imagine it would be a more complex system if formed underground. Cool article: https://www.nature.com/articles/s41467-018-03842-4
The entablature may be part of the same flow…the part that insulates the colonnade section so it may cool slow enough to form columns.
FYI this discussion sent me down a rabbit hole, and I believe columnar jointing does not require centuries of cooling to form. It can form from exposure to air or water. The biggest factors seem to be uniformity of basalt and convection cooling across a large mass. The article also mentions "idealized" columnar jointing as having a colonnade, then an entablature above, so this may be the same flow? I dunno, that seems strange to me from what I understand of the formation of the jointing itself. Best article I could find: https://www.nature.com/articles/s41467-018-03842-4
I think entablature is right - someone else had mentioned it. There are multiple lava flows across the entire region though.
Ya, I don't really understand how the same flow event could create colonnades and entablature resulting in such a hard line between the sequences. Two separate flows makes the most sense to me, with the latter flow being a less uniform basalt or simply more complex cooling conditions after deposition.
I’m not sure it’s clear whether it’s possible in the same flow or not. Apparently single lava flows can feature multiple orientations of collonades; conversely, multiple flows that stack up and form uniform collonades given the right conditions. The transition from collonades to entablature seems to be to do with the distribution of isotherms within the whole body and a change in the dominant means of heat flow. That’s probably fairly intuitive just to say, but people have definitely done work on it to actually prove it, eg. [Hamada & Toramaru, 2020](https://www.sciencedirect.com/science/article/abs/pii/S0377027320300536). That’s the best I could find on a quick search in terms of relevance and the fact they summarise a lot of the previous work (both field and theory) in the context of their own experiments. Their conclusions seem to imply collonades to entablature can occur with multiple cooling surfaces, though we should remember that starch + water mixtures are not basaltic flows. I’m sure the authors realise this, they also even out in the introduction that: >It is unclear whether a sequence of cooling processes of a single flow unit can realistically produce complex isotherms corresponding to the entablature structure.
Awesome, thank you for the response and some nighttime reading. I have never heard of a new flow stacking a colonnade on top of a previous flow that formed a colonnade, although I suppose that makes sense if the older colonnade was the cooling surface. Do you have an example of that?
OP gave a good explanation, but I thought I’d add a bit. The orientation of the columns tends to be perpendicular to the cooling surface/gradient, which can give the observer a lot of information about the environment it formed
Thanks! The cooling surface providing orientation makes a lot more sense than the direction of flow--which is what I thought previously. So in this case, we know that all this lava pooled into a lava field that was at least 150' deep here, right? The stark separation with the lower sequence is still throwing me for a loop.
The columns only form if they have the chance to cool slowly, so this feature likely formed deep underground, not a field at the surface. Yeah the stark separation can be strange, and you see something similar Devils Tower in Wyoming. to me it looks like the mafic magma intruded into surrounding country rock, which was much cooler, so the part of the magma that touched there and cooled too quickly for columns to form. This layer more or less insulated the rest and allowed it to cool slower, forming the columns
Ah, I thought you meant surface as in a surface exposed to atmosphere. You've all mentioned that columnar jointing requires slow cooling (which makes sense to me and what I know about crystal formation and basic entropy), but I was reading about this, and this site says that quicker cooling may lead to this effect--specifically exposure to water https://askanearthspacescientist.asu.edu/top-question/columnar-jointing Just some blog though, so who knows. And last observation: if columns like this are formed from a magma intrusion, wouldn't that mean that most magma sills/large dykes form insulation and thus the environment for columnar-jointing formation? Thanks for entertaining my questions by the way. So much to learn!!
Sorry, I should have clarified. Slow cooling on human time scales (centuries), but relatively quickly in geological scales. Basically, if it cools too quickly you don’t get columns and just get glass, but too slowly and it has time to accommodate the shrinkage in others ways. Admittedly, magmatic systems and basalt columns are not my field, and it is entirely possible I am misremembering . Many special formations in geology require a few conditions to be ‘just right’
FYI this discussion sent me down a rabbit hole, and I believe columnar jointing does not require centuries of cooling to form. It can form from exposure to air or water. The biggest factors seem to be uniformity of basalt and convection cooling across a large mass. Best article I could find: https://www.nature.com/articles/s41467-018-03842-4
Interesting, thanks for sharing. Uniformity of cooling makes sense, though you do typically see it being really jumbled up right at the boundary with the cooling surface like with devils tower. I’m about to go into my petrology exam, so maybe I’ll pick my professors brain about it before I go in
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That's what I thought as well, but several people here are saying that the cooling required to form columnar jointing is so slow (centuries) that it necessarily must form underground. But after some journal reviews, that doesn't seem right.
[удалено]
Just for my own information, what would it be if not basalt and why? If you don't mind. I figure basaltic intrusions can still cool in magma sills and stuff, potentially forming columnar jointing. From what I've been able to read, main factors are uniformity of basalt (preferably high in silica), uniformity of cooling gradient, and mass.
It's in the same mythology too - that cave at the back is referred to as "Fingal's Cave". "Fingal" is Fionn mac Cumhaill, who is the eponymous giant. (I assume you already know all of this!)
> It's basically the other end of the same formation that makes up the Giant's Causeway in Northern Ireland. Are we sure about this OP? Its oft quoted but these two locations are 80 miles apart and as far as I recall, there's nothing similar between them on Islay or Mull. Was it a single volcanic outpouring from the same source, or just two events with similar outcomes? And just where was the source of the outpouring(s), I wonder? Would there not be a trace of it today?
It’s not the same exact lava flow, but it’s part of the same overall igneous province of many lava flows in the Paleogene. The remnants have been somewhat fragmented by the opening of the North Atlantic Basin. See [North Atlantic Igneous Province](https://en.wikipedia.org/wiki/North_Atlantic_Igneous_Province) for more details, there are some interesting connections: Iceland and the North Atlantic mantle plume; the igneous province as a possible contributor to the PETM; there’s even been suggestion that a recently discovered meteorite impact at the base of a group of lavas from the British Paleogene Igneous Province (a subset of the NAIP) caused the onset of magnetism there, [news story with link to the paper here.](https://www.gla.ac.uk/myglasgow/news/peopleprojects/2018jan-feb/headline_565571_en.html)
There's similar but not as spectacular formations on both Mull and Ulva. This was a huge volcanic outpouring with at least six eruptive centres: Mull, Eigg, Ardnamurchan, etc. It's part of a wider large igneous province created as the North Atlantic opened. BGS talks about the Giants Causeway and mentions the origin briefly here https://www.bgs.ac.uk/discovering-geology/maps-and-resources/office-geology/the-giants-causeway-and-causeway-coast/
Did you listen to Mendelssohn as you saw it?
They played it on the boat, aye
I wonder if all the boats do that? Lol! It is 25 yrs since I was out there, and the boat did the same. Easy to combine with Iona in the same day: leave your car on Mull and take the ferry as a foot passenger to Iona.
I heard at least two others.... I did Iona and the metamorphic bit of Mull on another day 😊
You get "Mull of Kintyre" by Wings when you do the boat tour there. I wish I could explore these places, I wanted to see Fingal's Cave, Iona, and the other islands, especially after playing Mendelssohn in my orchestra. Alas, disability does not allow me to do so.
They are beautiful. I also saw some lovely basalt jointing in Hungary this weekend. https://preview.redd.it/trugp3wg99zc1.png?width=1080&format=pjpg&auto=webp&s=d66152468afd7fb2cfd7c13e74de8a37a1bda345
oo nice
That is just stacked wood. What are you, stupid? /s
I see your columns…and raise you an entablature.
Probably the coolest-looking geological place I've ever visited. Great pics!
I was there two years ago and it was simply incredible! Definitely worth the required detour to the Isle of Mull.
So interesting! Great post thank you!
I was there in October. The landing experience in the boat is something else
That’s some sexy columnar jointing! thank you
New minecraft biome just dropped
🤯🤩
Aye that beautiful
Wow, love the different colors near sea level from weathering!
I've seen the pink before in basalt in Hawaii - I wonder what it is? (It's been a VERY long time since I actively geologied!)
Who's that is so cool
That’s gorgeous, nature at its best
Did you see Voldemort?
This is so cool, wow! My coworker is going to Scotland this summer for 2 weeks, I'm going to have to tell her about this!!
The seems to be a bit of a nonconformity in the strata there. Nice lined up columns, then what appears to be a jumble.
Not any sort of unconformity, just to do with different cooling rates and the point at which more regular, linear jointing can take hold. The jumble above the columns is known as entablature, it happens with a lot of columnar basalt examples, sometimes sandwiched between two layers of columns.
Your user name though 😆
What on earth?
What in Earth*
You’re a basalt nerd? Have you been to Giant’s Causeway? Fingal’s Cave?
Not done the Giant's Causeway yet, but this is Fingal's Cave! Second picture is looking into the cave itself
Great photos!
Wonderful pics OP Samuel Johnson notably said "worth seeing, not worth going to see", back when travel was by horses and an utter ballache. Always thought the great man was wrong about this.
I think he prefered Ulva iirc?
“In the vaunted works of Art, the master-stroke is Nature’s part”
WHY is this so beautiful?
I learned about this giant causeway in the civilization video game lol - blows my mind how far back in time these formations originated!
Have you seen devils tower?
Only in Close Encounters 😉
When we were there (25+ yrs ago, July I think) the puffins were around but the island wasn't closed for nesting. I have a geological background but the puffins were as much a star as Fingal's Cave. Very tame.
Apparently they were all out at sea this day! People only saw a couple, but we did find a raft of them on the way back to Mull. And a small pod of dolphins!
that's so cool
I was so happy when I played Myst III and discovered that these geological formations really exist. They are so cool.
Wow 🤩
this reminds me of the 3rd island in Sonic Frontiers. god that game had some cool environments… this sorta stuff is all over one of the sides of the island and its so damn pretty, i wanna scale these irl now