Earth’s outer shell is made of two materials whose different densities and thicknesses give rise to two distinct “levels” on the planet’s surface.

And evidently these two materials—continental crust and more dense oceanic crust—have cute faces, as seen in the video above. How are mountain ranges made and why is continental crust four times thicker than the ocean crust? MinuteEarth describes this double-humped elevation distribution curve and more in Why Earth Has Two Levels.

Next: What is sea level? What counts as a mountain? And how was the Mariana Trench formed? Then watch more videos from MinuteEarth and try this experiment from San Francisco’s Exploratorium: Speed up geologic time with a DIY squeeze box.

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