【The world record is only…】How far can the ground be dug?

Chi-ga kun

Hakase! How far can the ground be dug? It seems to me that if you dig the ground, you can go anywhere…?

Hakase

Well, that’s a good question. Let me explain how far the ground can be dug!

Have you ever seen a scene in an animation where a machine with a drill easily penetrates the earth?

Is such a thing possible in reality?

In this article, let’s learn together with Chi-ga kun and Hakase how far the ground can be dug!

When did humans reach the center of the earth?

Hakase

Let’s start with this, Do you know when mankind reached the center of the earth?

Chi-ga kun

Let’s see, humans reached the moon in 1969, right? Asteroids so far away from the Earth have already been reached by probes, right?
So that means that the center of the earth was reached by…

Hakase

But the fact is, mankind has never reached the center of the earth!

Chi-ga kun

Eek! The moon, Mars, asteroids, Pluto… we’ve made it into the vastness of space, but we haven’t reached the center of the earth!

What is the world record for drilling into the ground?

Hakase

So, Chi-ga kun, how far do you think mankind has ever dug?

Chi-ga kun

It looks like it goes pretty deep up there!
Even I could reach the mantle if I wanted to! (lol)

Hakase

Is that true? If so, I’d love to have you help me drill next time!
(Not knowing that mankind has never reached the mantle…)

Chi-ga kun

So, Hakase! What is the answer?

Hakase

40,230 feet (12.262 km). The drilling was conducted by the former Soviet Union in 1989.

Chi-ga kun

What!? 12 km is only 0.19% of the Earth’s depth, considering that the radius of the Earth is 6,400 km!

Hakase

That’s right. Moreover, it took 20 years of drilling to complete the project, until 1989. Even after such a long period of time, there was a limit to the amount of time that could be spent drilling.
By the way, Chi-ga kun, do you notice anything from the fact that humans have only been able to drill about 12 km?

Chi-ga kun

Hmmm.
Ah, as I studied in “【Learn by illustration!】Differences between continental and oceanic crust“, the thickness of the continental crust is 30-50 km, right?
If so, does that mean that humans have never reached the mantle yet?

Hakase

That’s right. Mantle materials have been collected in places like Mt. Apoi in Hokkaido, where the mantle was revealed to the surface as a result of the collision of continental plates.
However, it has not yet been possible to reach the mantle by drilling.

Chi-ga kun

Yes, I see, I take back what I said a minute ago.
Still, in the anime, there are often scenes where drills penetrate the earth, right? Why can’t it be like the animated scene?

Why it’s not like an animated scene

Hakase

The reason for this is the ultra-high temperature and pressure.

Hakase

Beyond a few dozen meters in depth, the temperature increases with depth. This is called the subsurface temperature increase rate, and it averages 2-3°C per 100 m!

Chi-ga kun

If the rate of increase in underground temperature were to increase by 3°C per 100 m, then digging 12 km would result in a temperature increase of 360°C…!
That’s a huge temperature increase…!

Hakase

Similarly, the pressure increases as drilling proceeds. The pressure near the boundary between the crust and the mantle is calculated to be approximately 134 GPa.

Chi-ga kun

On level ground, it is 1 atmospheric pressure. That’s 1,340,000 times that!
That’s a lot of pressure…!

Hakase

Yes, it is. It is necessary to build a machine that can withstand such ultra-high temperatures and pressures.

Summary

Hakase

This article explains how far the earth can be dug. Even with all the advances in science and technology, it is still very difficult to reach the center of the earth.

Chi-ga kun

How to counter ultra-high temperature and ultra-high pressure…
I’m looking forward to seeing more technological advancements in the future!
Hakase! Thanks for teaching me today!

Thank you for reading to the end!