Bad Geology Movies: Dante’s Peak, 1998

Dante’s Peak

1998

Pierce Brosnan, Linda Hamilton

Premise: What if a seemingly dormant volcano in the Cascades suddenly exploded back into life?

As “Bad Geology Movies” go, Dante’s Peak is not the worst. It has some errors, but at least it gets quite a few things right:

1) The Cascades is a great place to have a volcano suddenly go off, because it is volcanically active and it has had volcanoes (relatively) suddenly explode. Mount Saint Helens, in 1980, only gave a few months of warning before it blew its top. Other volcanoes have been known to go from dormant to exploding in even shorter time frames.

2) The killing of plants and fish by carbon dioxide emitted from vents originating from deep magma bodies is also known to happen. But this does not always mean eruption is imminent.

The movie was not without its errors however.

1) I found it troubling that the volcanologist, played by Brosnan, seemed not in the least bit alarmed by a pH of 3.58 in the mountain lake. That’s a pretty low number, which means it’s pretty acid. With a pH so low, the fish in the lake would surely have been affected in some obvious way (especially since the carbon dioxide had already killed trees). I wouldn’t go in that lake.

2) When the volcano first went off, there was a severe lack of lahars. Lahars are fast-moving slurries of ash, mud, and water that tend to take out towns at the bases of volcanoes. Usually, the water comes from the sudden melting of the snow and ice capping the previously quiet volcano. Dante’s Peak had a significant snowcap, but there were no lahars, at least not right away. There finally were some lahar-like flows toward the end of the movie, but I felt like they needed to be earlier on.

3) Brosnan’s character shouts during an earthquake, “They weren’t tectonic! They were magmatic,” suggesting that somehow, by the way the Earth shook he could tell that the earthquake was not from motion on a fault, but from the movement of magma below the surface. In real life, a person experiencing an earthquake first-hand is not going to be able to make such a distinction.

4) The flows! Ah, the flows! They’ve mixed their flows! An eruption such as this is most likely to only have magma (lava once it erupts) of a single composition. The composition of a magma (how much silica, iron, and magnesium it has, for example) dictates how it flows. One of the earlier eruptions of the volcano has smooth, fast-flowing, ropey magma (known as pahoehoe), indicative of what’s called “Mafic” magma. Later, the characters are stopped by a slow-moving, lumpy flow, similar to what we call A’a’. This type of flow is more expected of “intermediate” to “Felsic” magmas. The truth is that one would not expect mafic magma from a volcano in the Cascades. If I recall, I laughed out loud when I saw that fast flow chasing down the main characters. The slow-moving, lumpy flow is more of what we would expect from a volcano in the Cascades.

5) Whatever the composition, it must be said that one would never, ever be able to drive a truck across an active lava flow. The heat would be so intense that the vehicle and its occupants would begin to burn almost immediately. The main characters should have been incinerated. But it’s Hollywood, so that’s ok.

6) Speaking of characters being killed, there were two more ways in which the entire cast should have died. First, inhaling all that ash that was snowing down would be lethal. It’s nothing more that microscopic shards of glass. Any animal inhaling that would die of massive hemmoraging in the lungs. As it happens, this is how some of the most spectactular fossil localities that we have were formed. Second, when they all stopped to look back and watch the volcano explode, they weren’t far enough away to be safe. The ash and debris would have buried them, if a mudslide hadn’t of taken them out.

But all told, the premise of the movie was realistic – much moreso than others I have watched of late. There is definitely some Hollywoodization taking place, but it has to be there.

I liked the movie and only cringed a few times because of bad science.

If you want a different insight into the film, check out this website.

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