Misconception – The Earth’s core is hollow, or that large hollow spaces occur deep within Earth

There are many misconceptions about geological concepts. There is a list here, developed by Kent Kirby of the University of Minnesota. This post is to debunk one of those misconceptions. There will be others. Find them here.

Misconception: Earth’s core is hollow, or that large hollow spaces occur deep within Earth

The idea of a hollow Earth has been propagated by many things, including popular movies like Journey to the Center of the Earth, and The Core. There are also numerous religious groups that hold that the Earth is hollow and it is in this hollow center that either resides the Garden of Eden or maybe Hell itself. Some just think that the Earth must be hollow.

The Earth is not hollow. Nor is the interior of the Earth molten (with the exception of the liquid outer core), as I discuss here.

OK, so how do we know this?

Earthquakes. Yes earthquakes provide the answer.

You see, when earthquakes happen on one side of the planet, the vibrations created pass through the Earth and can be recorded by seismographs on other parts of the planet. These vibrations, or waves, that pass through the Earth are categorized as P-waves (primary) and S-waves (secondary or shear). The P-waves hit the seimographs first, followed soon after by the S-waves.

These waves differ in how they travel through the interior of the Earth. P-waves travel by compression, like sound does through the air. S-waves travel by a side-to-side motion, or shear.

What’s most crucial here is that P-waves will travel through solid and liquid materials. S-waves can only travel through solid materials.

When waves from an earthquake pass through the Earth and hit a seismograph on the other side, we can tell if the waves passed through liquid or solid rock, depending on whether or not we see S-waves. Great hollow caverns in the Earth (or a liquid mantle) would be completely obvious. The only feature in the Earth’s interior that eliminates S-waves is the liquid outer core.

Thus, we know without any doubt that the Earth is not hollow.