Sourced from Volcanoes Are Hot: Oliver’s Great Big Universe #2 by Jorge Cham. September 2024. Published with permission from Amulet Books, an imprint of ABRAMS.
The earth looks a lot like a boba tea drink.
You know those boba tea drinks they sell in some stores where they shake it, but when they give it to you, all the different things in it have floated to a different spot in the cup? The ice floats to the top, then the fruit pieces float underneath, and the boba balls all fall to the bottom?
Well, the same thing happened to Earth. When it was a big ball of lava billions of years ago, all the different things in it floated to another level. The lighter rocks floated to the top, the heavier rocks floated just below, and all the metal stuff sank to the bottom.
The Earth is roughly round, so when the heavy stuff sank, it went to the center of the Earth, and when the lighter stuff floated, it went to the outer part of the Earth.
This makes the inside of the Earth look like what happens when you cut an avocado or a hard-boiled egg in half, and you can see all the layers.
I told my aunt to have someone make a boba tea drink with avocado and eggs, and she said that wouldn’t help my bathroom situation at all.
My aunt says that if you tried to dig a hole on the other side of the Earth, this is what would happen: First you would dig through loose stuff, like dirt or sand. It could be a little bit, but it could also cover an entire football field (about 0.1 kilometer).
Then you would hit the first layer of stone.
The dirt and rock layer are called the crust. That’s because it is. . . crispy. It is usually made of rock that is extra brittle or crumbly. It is 5 to 70 kilometers thick, which seems like a lot, but it is quite thin compared to the entire Earth. It is about the thickness of an eggshell for its egg.
Then the second layer you have to dig through is called the mantle. This is made of heavier rocks and is quite thick. You’d have to dig 1,700 miles to get through.
The mantle is where lava comes from. There it is formed as magma before shooting up through the cracks in the crust. If you ever dig through the mantle, you better hope you don’t accidentally dig into some magma.
After the mantle is the core of the Earth. This is a large ball in the center of the planet that is made mostly of a metal called iron. The first 1,400 miles of it is called the outer core, and it’s moist and molten, meaning you can’t dig through it. And at the center is a solid metal ball called the inner core, which is 1,500 miles wide.
So if you tried to dig to the other side of the world, it would take a long time, you’d encounter some magma, and you’d have to swim through liquid metal and cut through solid iron.
Not only that, my aunt said it’s SUPER HOT in the Earth. It’s still a bit hot from when the Earth was a big ball of lava, AND there’s a lot of radioactive stuff in the Earth, which heats up the rocks and metal.
The Earth’s surface is nice and cool because we are close to space, which is very cold. But in the mantle the temperature is 3,500°C and in the core it is 6,000°C. That’s quite warm when you consider that the surface of the sun is also about 6,000°C.
There is also a lot of pressure inside the Earth. That’s because of all the rock and metal trying to compress due to gravity. If you dug that deep you’d be crushed to a pulp pretty quickly.
Speaking of busy, I still had to go to the toilet.
Jorge Cham is the best-selling, Emmy Award-nominated creator of . . . many things: from the popular PBS show Elinor wonders why named after the popular non-fiction book for adults We have no ideaalong with the popular podcast Daniel and Jorge explain the universe and the popular webcomic PHD comics. He is without a doubt an expert at explaining things about the world in interesting and fun ways. He received his PhD in robotics from Stanford University and was a lecturer and research associate at Caltech from 2003 to 2005. He is originally from Panama.