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Krubera Cave, one of our planet's deepest known caves, extends 2200 meters into the earth - that's a depth of nearly six Empire State Buildings. Or at least, that's as far down as humans have been able to explore; there might be other undiscovered chambers that go down even farther. But the cave can't be that much deeper, because there's a limit - actually, three limits - to how deep caves on Earth can get. Hi, I'm Cameron, and this is MinuteEarth. The deepest caves - like Krubera - form when slightly acidic water finds its way into the small cracks in a layer of water soluble rock - usually limestone.
Over time, the water dissolves the limestone, carving ever wider caverns. But at a certain point, if the cave keeps going downward, the limestone runs out; below, there's typically a layer of rock that the water can't dissolve easily. S o the first limit to a cave's depth is how deep the water-soluble rock goes. Mammoth Cave, the largest cave network in the world, only extends 118 meters down because the dissolvable rock layer is pretty shallow. The limestone layer that Krubera cave is carved from is much thicker, allowing for a deeper cave. But even if there were limestone all the way down to Earth's mantle, Krubera couldn't keep
on going much further because of the second limit on cave depth: sea level. Cave chambers tend to form where acidic surface water meets water soaked into the rock like a sponge, this is a point called the water table. The water table can move up and down, but the lowest it can generally go is sea level. That's why, even though Krubera Cave extends 2200 meters down, its deepest parts are STILL higher than the nearby Black Sea; the cave only got so deep because the entrance is so high up. Which brings us to the third thing that limits a cave's depth: the pressure of the rock above it.
Past a certain point, any opening in the Earth's crust will be crushed by the immense weight of the stone above. For limestone caves like Krubera, that point is around 2500 meters deep. So while Krubera might extend a bit past where we've currently explored, it can't be that much deeper. With that said, there ARE much deeper holes in the Earth's crust, they're just only possible through human ingenuity. Like, engineers reinforced a 4000-meter-deep mine in South Africa with steel rods and cement strengthened with diamond-coated rebar so the tunnels can withstand the crushing pressure.
And by actively drilling through rock - instead of relying on water to dissolve it - we can dig through undissolvable rock go way past sea level,and di to places where the pressure is absurdly high - just look at the Kola Superdeep borehole, which extended a mind-boggling 12 kilometers into the Earth. It's not natural, but it is deeper. A hole heckuva lot deeper. Talk about rockin 'out. To "burrow" a phrase, we shouldn't take that ingenuity for "granite". That would be abysmal. Do you dig what I'm saying?
[Arcadi:] Ok grampa, let's, let's… let's put it to bed… ok. If a bunch of giant cave holes start appearing in the Earth tomorrow, you'll certainly hear about it on the news, with some outlets likely reporting that they're the result of rampant fracking while others insist that they're part of the planet's naturally occurring terraforming cycles. If so, to help you understand how news coverage differs across different parts of our reality spectrum, you'll want to use Ground News, this video's sponsor. Like, take this story that I found on CNN about how some recent heat waves can be linked to specific polluters. I know CNN can sometimes be biased, so in order to see how other outlets were reporting it, I went to Ground News.
The site aggregated links to the story in one convenient place and rated all the various news outlets that covered the story in terms of factual reliability and political bias. I can see that almost 50% of the outlets reporting this story are considered left-leaning, and no major right-leaning news agencies have mentioned it at all. That's what Ground News calls a "blind spot" which is cool, because it shows you news stories not being reported by the media you might typically consume. Ok, to cut through the sensational and get down to the substance go to ground.news/earth. You'll get 40% off their vantage plan which is what we use.
