The outer layer of the Earth, the crust, isn’t all one piece. It’s made up of many shifting pieces, like a giant jigsaw puzzle. Those pieces are called Tectonic Plates. They’re moving around all the time - the ground beneath your feet is actually moving right now. It's just so slow that we don’t notice it - the fastest they go is about 4 inches per year. When tectonic plates get stuck while moving past one another, eventually they will break through the part that was stuck, and that big movement is what we feel as an earthquake.

The core of the Earth is a solid ball about ¾ the size of the Moon. We haven’t been able to observe it directly, but we can make guesses about it based on analyzing how waves created by earthquakes bounce around, and by looking at the Earth’s magnetic field, which the core has a lot to do with. Scientists believe the core is made mainly of an iron-nickel alloy, and to be about 9,800 °F, or 5,430 °C - about the temperature of the surface of the Sun.

The biggest earthquake ever recorded happened on May 22, 1960 just off the coast of southern Chile. It generated a massive tsunami (giant wave) that traveled all the way across the Pacific Ocean to cause destruction in Hawaii and Japan.

The Earth is round, and so is every other planet we’ve ever discovered. Is that a coincidence? Nope! Planets are round because of gravity, pulling everything inward all the time. The only stable resulting shape from a constant force like that is a sphere - anything else would be sort of smoothed out. It’s sort of like if you took a lump of clay and rolled it around on the table, applying even pressure from all sides. Eventually, it would become a sphere, and that’s similar to why the Earth and other planets are shaped the way they are.

Scientists estimate the Earth is 4.54 billion years old (give or take 50 years). Scientists figured this out by measuring the ages of certain rocks and meteorites. They use meteorites because they assume that meteorites formed around the same time as the Earth did, and because rocks on Earth may have been melted down and mixed with other rocks over the course of 4 billion years, making them less likely to have been around unaltered since the formation of the Earth.

The Earth’s outer layer, the crust, is made up of a bunch of different pieces that are constantly moving around. When two pieces push against one another, they will eventually crumple, pushing the land above them upwards. If you take two pieces of aluminum foil and push them slowly into one another, you can see a similar process take place.

Mt. Everest is higher above sea level than any other mountain, but it’s not necessarily the biggest. After all, why should we measure mountains by how high they are above the surface of the sea? What about mountains that start underneath the sea? Measured from base to peak, Mauna Kea in Hawaii is the tallest mountain on Earth, beating out Mt. Everest by around 4,000 feet (or 1400 meters).

As rain water seeps into the ground, it picks up small amounts of carbon dioxide gas, creating carbonic acid - which is also in the soda you drink (soda is acidic!). As the water seeps down, it may pass through limestone, and if it does, it will dissolve a mineral called calcite that’s in the limestone. When that water finally reaches a cave, the carbon dioxide is released into the air - just like when you open up a can of soda. That makes the calcite un-dissolve (or redeposit) at that point. Over time, the calcite builds up, creating stalactites (which hang from the ceiling) and stalagmites (which come up from the ground).