When I was a kid, I liked to dig holes in my yard in Cincinnati. My grandpa joked that if I kept digging, I would end up in China.
In reality, if I hadactually been able to dig straight through the world, I would have come out in the Indian Ocean, about 1,100 miles (1,800 kilometers) west of Australia. That’s the antipode, or opposite point on Earth’s surfacearea, from my town.
But I just had a garden spade to relocation the earth. When I hit rock, less than 3 feet (1 meter) listedbelow the surfacearea, I couldn’t go muchdeeper.
Now, I’m a geophysicist and understand a lot more about Earth’s structure. It has 3 primary layers:
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The external skin, called the crust, is a extremely thin layer of light rock. Its density compared to Earth’s size is comparable to how thick an apple’s skin is to its size. When I dug holes as a kid, I was scratching away at the really top of Earth’s crust.
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The mantle, which lies below the crust, is much thicker, like the flesh of the apple. It’s made of strong, heavy rock that flows up to a coupleof inches per year. Hotter rock increases away from Earth’s center, and cooler rock sinks towards it.
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The core, at Earth’s center, is made of super-hot liquid and strong metal. Temperatures here are 4,500 to 9,300 degrees Fahrenheit(2,500 to 5,200 degrees Celsius).
Earth’s external layers apply pressure on the layers beneath, and these forces boost gradually with depth, simply as they do in the ocean – think of how pressure in your ears gets morepowerful as you dive muchdeeper undersea.
That’s appropriate for digging through the Earth since when a hole is dug or drilled, the walls along the sides of the hole are under significant pressure from the overlying rock and likewise unsteady since there’s empty area next to them. Stronger rocks can assistance larger forces, however all rocks can stopworking if the pressure is excellent enough.
(Credit: Volcan26/Wikimedia, CC BY-SA) The Earth is made up of layers. The lithosphere is the strong, external part of the world, consistingof the fragile upper part of the mantle and the crust.
When digging a pit, one method to avoid the walls from collapsing inward under pressure is to make them less high, so they slant outside like the sides of a cone. A great guideline of thumb is to make the hole 3 times larger than its depth.
Unstable Walls
The inmost open pit in the Earth is the Bingham Canyon Mine in Utah, which was dug with excavators and dynamites in the early 1900s to mine copper ore. The pit of the mine is 0.75 miles (1.2 kilometers) deep and 2.5 miles (4 kilometers) broad.
Since the mine is more than 3 times larger than it is deep and the walls are sloped, the pit’s walls are not too high or unsteady. Still, in 2013, one of the slopes collapsed, triggering two substantial landslides that launched 145 million heaps of crushed rock to the bottom of the pit. Luckily, no one was harmed, however the landslides triggered hundreds of millions of dollars in damage.
Suppose you were to shot digging through