1- Hi, it's Doug.
2I recently moved to Austin, Texas,
3and there's so many new things I'm looking forward to checking out.
4Now, I moved here during the summer when it's really hot
5so one thing I'm really looking forward to is visiting a swimming hole.
6Texas is famous for its swimming holes.
7These are naturally occurring pools of water,
8usually connected to an underground cave system.
9Like, check this out.
10This swimming hole is called Jacob's Well.
11You notice how dark it looks?
12That's because the bottom is over 140 feet down,
13but I've heard that that water feels nice and cool on a hot day.
14Someone named Brayden has a question about holes in the earth.
15Let's give Brayden a call now.
16- Hi, Doug.
17- Hi Brayden.
18- I have a question for you.
19What's the deepest hole anyone has ever dug?
20- Ooh, that's a great question.
21People have been digging holes for a long time
22and for a lot of different reasons.
23Some people dig holes just for fun like this person named Ra Paulette.
24He's been digging holes for over 25 years, but not just any holes.
25Check this out.
26Isn't that incredible?
27These holes he digs by carving into a soft type of sandstone rock are beautiful works of art.
28The amazing thing is he digs them all by himself with no tractors or machines to help.
29Some of them, like this one, are even homes you can live in with a bathroom and kitchen,
30so cool.
31But people don't only dig holes for fun.
32Thousands of years ago, people dug holes to live in like the builders of this city in Turkey.
33It's called Derinkuyu and it's the deepest city in the world.
34It's located as deep in the ground as a 20 story skyscraper is tall.
35No one lives down there now, but a long time ago, it could hold 20,000 people.
36Now, even though Derinkuyu is pretty deep, it's not even close to being as deep as this hole.
37This is the deepest hole anyone has ever dug by hand without the help of any machines.
38It's 1,285 feet deep.
39That's deeper than the empire state building is tall
40and it wasn't easy to dig.
41The deeper the workers dug, the darker it got,
42and they only had candles to light the way,
43but they kept digging day and night for four years
44until finally they found what they were looking for.
45Can you guess what it was?
46Water.
47The hole is called the Woodingdean Well and it was dug to find water to drink.
48See, there's actually a lot of water under the ground,
49a hundred times more water than all the rivers and lakes put together.
50So where water is needed, people dig holes to try to find it.
51But water isn't the only thing you can find when you dig.
52Sometimes people also dig holes to find valuable resources like silver or gold.
53That's what these miners in South Africa are looking for.
54The Mponeng Gold Mine is the deepest mine in the world.
55It's as deep as 10 Empire State Buildings stacked on top of each other.
56This hole is so deep,
57it takes miners over an hour on special elevators just to get to the bottom.
58And once they're down there, it's hot.
59At 140 degrees, it's hotter than the hottest day ever on earth.
60That's because the deeper you dig, the hotter it gets.
61Before I go on, I'm curious.
62Besides looking for water or valuable resources like gold,
63what are some other reasons you think people dig holes?
64Well, I'm not sure how you answered,
65but you may be surprised to hear that the deepest holes on earth were dug because people were just curious.
66They wanted to know what they might find way, way down, deep in the earth.
67Like this group of scientists in Germany.
68They were trying to reach a mysterious layer inside the earth called the mantle.
69Using special drills, these scientists were able to dig a hole that went almost 30,000 feet deep.
70Now that's deeper than the world's tallest mountain, Mount Everest, is tall.
71It's called the KTB Borehole
72and it's the second deepest hole ever dug.
73But even though they dug pretty deep, they weren't able to reach the mantle.
74They did leave the hole open for people to visit, though.
75If you're ever in Germany, you can check it out.
76Okay. If you think that's deep, remember, I said that was the second deepest hole ever dug.
77This is the Kola Borehole in Russia.
78It is the deepest hole on earth.
79Using special drills, workers dug for over 20 years
80and they got pretty far, 7.5 miles down.
81That's deeper than 30 Empire State Buildings stacked on top of each other.
82But don't worry, it's only about as wide as a dinner plate,
83so there's no way you can fall in.
84So were they able to reach the mantle?
85Not even close.
86In fact, if the earth were the size of an orange,
87then the Kola Borehole wouldn't even go past the peel.
88But why is that?
89Are the drills we use to dig just not long enough?
90Even though that makes sense, making long enough drills isn't the problem.
91The problem is heat.
92See, the closer you get to the mantle, the hotter it gets.
93It's so hot down there that normal drills can melt like ice cream when they go that deep.
94And it's not just the drills that melt down there.
95The rocks down that deep in the earth are so hot
96that they start to act almost like a thick, gooey liquid,
97almost but not quite as hot as lava.
98So it doesn't look like we'll be digging a hole all the way to the other side of the earth anytime soon.
99Still, scientists are curious to figure out if there are new ways to dig even deeper.
100If this is something that interests you, maybe it's something you'll help figure out one day.
101But until then, it's important to know that digging deep holes on your own can be dangerous,
102so if you do try to dig, never dig a hole that's deeper than you are
103and make sure you always have an adult nearby to supervise.
104That's all for this week's question.
105Thanks, Brayden, for asking it.