Bad Geology Movies: The Core, 2003

The Core


Aaron Eckhart, Hilary Swank

Premise: What if the Earth’s liquid outer core stopped spinning, resulting in total catastrophe? Can it be set spinning again?

One thing this movie got right: the Earth’s magnetic field is generated in the liquid outer core. The rest, well—

I enjoyed the opening scene with the main character giving a geology lecture about using seismic waves to understand the interior of the Earth. I’ve given that very lecture. I’m just glad my students aren’t so lethargic. It’s pretty amazing actually, since my classroom is considerably darker. I do have one student who’s often working on his nails, but that’s ok. He plays classical guitar.

Moving on to the geological problems with this movie, and there are many…

1) The whole movie oversimplifies the structure of the Earth, dividing it only into crust, mantle, and inner and outer core. It’s substantially more complex than that. The mantle is divided into two parts (upper and lower), and the movie fails to distinguish between the lithosphere (crust and uppermost mantle) and asthenosphere (part of upper mantle). That’s fine though, I guess. If they keep it simple, they can’t be wrong.

The structure of the Earth

2) As our intrepid terranauts are drilling toward the core and about to pass from the crust to the mantle, one of the ground crew comments that passing through the crust is different than the mantle as “the crust is just rock.” Last I checked, the whole planet was ‘just rock,’ with the only possible exception of the liquid outer core.

3) Our explorers find great empty spaces in the mantle, filled with amethyst crystals. Two problems here: a) Any empty spaces would have been most likely recognized by the behavior of seismic waves through the mantle. Shear waves won’t pass through liquids and NO waves would pass through an empty void. There are no empty spaces in the mantle. B) These (impossible) empty cavities are filled with huge amethyst crystals in the movie. Amethyst is a variety of quartz. If one takes a moment to look at Bowen’s reaction series, one would find that quartz is common in felsic rocks, like continental crust. The mantle is ultramafic rock. There isn’t enough silica to make quartz. Quartz would not be stable there. Quartz does not exist in the mantle. But, to give credit where credit is due, at least they got the shape of the crystals right!

4) Somewhere low in the lower mantle, our terracraft bumps into (literally) a bunch of enormous diamonds. I can see the movie-maker’s thinking here: Diamonds form under intense pressure, thus there must be huge diamonds near the Earth’s core. One problem though. Diamonds are composed entirely of carbon. There just isn’t enough carbon in the mantle to make diamonds. At all. Certainly not the gigantic ones portrayed in the movie. That point aside, I have no idea on what basis the identification as ‘diamond’ is made. They certainly don’t have the proper octahedral shape of diamonds. I guess because they show up as black and are thus impenetrable, then they can only be diamonds.

5) They set off the nukes and achieve “full rotation” of the liquid outer core (whatever that means). As I understand the flow of the outer core, it’s not quite as simple as shown in the movie. We call the flow of the liquid outer core, and how it generates the Earth’s magnetic field, the magnetic geodynamo. This link will take you to several other pages that will explain better how this works.

6) The final facepalm of the movie was when the terracraft finds itself launched out from the core and back to the sea floor through a “space between tectonic plates near Hawaii.” Hawaii is smack-dab in the middle of the Pacific Plate. There are no plate boundaries there. Now it is a hot spot, and the crust might be thin, affording an easy exit for our terranauts, but there is no plate boundary.

So these are the major geologic problems with the movie “The Core,” or at least the ones I spotted in the feverish state I was in while watching the film. Read my review of “Journey to the Center of the Earth,” for a completely different yet equally incorrect perspective on what Earth’s interior might be like.

Be careful should you start to think that what’s portrayed in movies has any basis in reality (at least as is understood by science).

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