I know the Soviets dug the deepest man made hole back in the 70s, and it seems nobody has tried anything like it since, I assume for good reasons. Is there anything to be gained? Would it benefit humanity in any way to make another attempt with 50+ years of technological advancements? I think the Soviet hole disproved the idea of the “basaltic layer” ~6 miles in the ground, but perhaps we know a lot more about what lies beneath Earths’ surface now. I really do not know!
Comments
>I know the Soviets dug the deepest man made hole back in the 70s
While a bit semantic, for getting a sense of the appropriate scale it’s worth clarifying that they didn’t dig a hole, they drilled an ~9 inch wide borehole, specifically the Kola superdeep well. Still a technical feat, but decidedly different than digging something akin to a mineshaft to those depths. Also, while drilling began in the 1970s they didn’t hit the record depth until 1989 (it was not constantly active for that whole time, i.e., it did not take 20 years of consistent drilling to reach that depth or something) and activities continued there until the mid 90s.
>and it seems nobody has tried anything like it since, I assume for good reasons.
That’s not really true. There were a variety of deep wells that both preceded and followed Kola. This section of the Kola wiki discusses a few of them, e.g., Project Mohole, which was an attempt to drill into the mantle – that preceded Kola, but effectively kicked off things like the DSDP, ODP, and IODP, which along various other drilling programs have drilled a lot of holes in the crust for research purposes, though none have reached the depths of Kola and the majority of these are relatively shallow in comparison. However, sites like KTB in Germany and Shendi Take 1 in China have come relatively close to the depths of Kola in the time since.
> Would it benefit humanity in any way to make another attempt with 50+ years of technological advancements?
As discussed above, it’s not as though Kola was the last time we engaged in concerted efforts to drill into the crust for scientific research. From compiled maps of site locations for programs like DSDP, ODP, and IODP, which focused on drilling in the oceans and the International Continental Scientific Drilling program, you can see that we’ve drilled in a relatively large number of locations for scientific purposes (there are of course a lot of other drill sites done for industry, and some data from these is available publicly, but a lot of that is held privately). Now, for the vast majority of these, they have very specific scientific targets and very few (if any) have a specific goal of “drilling as deep as possible”. Similarly, if you look up the details of most of these, they were drilled to a fraction of the depth of Kola or comparable “super-deep” wells.
In a general sense, and in a more direct answer to your question, yes, drilling very deep holes would still of course be scientifically important, in large part because what more shallow drilling, like those documented above, has highlighted is that there is a lot of variability pretty much everywhere, so we would undoubtedly learn something new with more super-deep holes in nearly any location. That, however, ends up being both the reason for and against attempts to drill super-deep holes. I.e., given that there is pretty much always limited resources in terms of money, time, and equipment for these kind of endeavors, the choice generally has been to go for coverage and more drill sites in more locations than a concentrated effort to drill really deep in a smaller number of locations, in large part because the cost and effort of drilling increases dramatically with depth and we can presumably learn more with a greater number of shallow holes than a handful of very deep holes. That being said, there are still lots of discussions about trying to drill into the mantle in semi-normal areas of the ocean floor (as opposed to successful attempts to drill into the mantle in regions where sections of the mantle are somewhat anomalously shallow, like the location documented in Lissenberg et al., 2024), e.g., this piece that goes through a lot of the history of prior attempts, but even with technological improvements, it remains a very costly effort that generally has not been an appealing use of resources, especially in the context of things like the fact that the US ship that drilled a lot of the ODP and IODP holes has been retired with no planned replacement.
I remember back in high school, I got super obsessed with geology after this one field trip where we got to visit an old quarry. Our guide was talking about how each layer of rock tells a story, like going back in time. That stuck with me for years. I even did a whole science fair project on core sampling and how deep drilling can reveal ancient climate data. It blew my mind that we could learn about volcano eruptions, asteroid impacts, and even ancient microbial life just from digging down far enough. My project didn’t win anything but it kinda sparked this lifelong curiosity about the Earth and what’s literally beneath our feet.
Later on in college, I took a few earth science classes and learned about stuff like the Kola Superdeep Borehole, and it just made me wish we invested more into that kind of exploration. I know it’s expensive and technically insane to drill super deep, but who knows what we’d find? There’s still so much mystery in the ground below us. And with all the tech we got now, it feels like we’re missing out by not digging deeper—literally. It’s not just about oil or gas, it’s about understanding the planet and even maybe figuring out how to better predict earthquakes or other disasters.
I did see a short bit on a company working on some tech for super deep holes but its still in early stages. They’re using high pressure air and an electric arc to vaporize rock vs drilling through it. It doesn’t make sense from a viability standpoint because of its speed and power requirements until you get past a certain depth, and I think there are some unknowns with how it’ll deal with fluid/gas pockets and stuff, but it seems cool.
The cost just starts going up rapidly the further you go down.
I read somewhere that somebody was developing x-ray lasers for vaporizing rock for deep borehole drilling. At least there isn’t a drill bit to melt when it gets hot deep down in the ground.
The reason they wanted to develop this is for geothermal electrical generation. If you can easily make a hold deep enough and pump some water down there, you can use the steam to drive turbines and have essentially limitless carbon free energy…. in theory.
Imagine being able to drill a geothermal energy well pretty much anywhere on Earth (within reason).
This company (https://www.quaise.energy/) is trying to drill 10-12mile deep holes through which they can pump water, let the earth heat it to supercritical steam, and use it to run a traditional turbine and generate “free” electricity. This could be an amazing unlock because it can put baseload energy near point of use without any combustion or nuclear byproducts.
Edit: if you’re curious, they’re “drilling” using high powered lasers to ablate the rocky material rather than traditional rotary/mechanical material removal.
One way in which these super deep drillholes are irreplaceable is as a validation technique for the geophysical methods used to predict the rocks at depth, specifically active seismic surveys. In the case of the Kola hole, the predictions made from seismic ultimately proved incorrect, which meant that the methods being used to interpret the survey results and model the results weren’t accurate at depth.
There’s really no substitute for drill data when it comes to that: you can have all the data and all the complicated maths in the world, but you can’t know whether it’s correct without a drill hole.