Bad Geology Movies: Dante’s Peak, 1998

Dante’s Peak


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.

11 thoughts on “Bad Geology Movies: Dante’s Peak, 1998

  1. I hate when they talk about a movie being realistic. It’s a movie non of it is realistic just enjoy the movie.

  2. I hate when they talk about a movie being realistic. It’s a movie non of it is realistic just enjoy the movie.

  3. I hate when they talk about a movie being realistic. It’s a movie non of it is realistic just enjoy the movie.

  4. I hate when they talk about a movie being realistic. It’s a movie non of it is realistic just enjoy the movie.

  5. The truck scene over the lava sent me over the edge and to this review. I am no scientist but I do know that the truck would not have made it 15 yards in that lava.

  6. I like your style, Penny. I too enjoyed this movie however much it was hollywoodized. I think the director had some appreciation of our ‘craft’ and a scholastic background in it. Not many flicks out there that can really do justice to the awe inspiring magnitude of this field

  7. I was curious, was that acidic lake scene where grandma Ruth sacrifices her life to save the family and yet the scientist who paddles with a coat over his arm and go unscathed, legit. I thought it was silly how the water melted the boat away and killed grandma Ruth (stubborn women) my father who is a doctor says it’s possible for the body to die of shock or infection especially in those conditions. But my question is the water that dangerous and acidic with a volcano?The movie was on tv tonight I was sick and it was either this show or reruns of how I met your mother.

  8. Kat, I was curious about the science behind the lake, too.

    It turns out that, yes, lakes around or on a volcano can get that acidic, though arguably the heat and potential tsunamis are probably more dangerous.

    In the movie, he measures the water in the hot springs at a pH of 3.48, making it less acidic than common household vinegar (pH is a logarithmic scale, so the roughly .75 point difference is fairly large). Given the kids’ comments and the effects of carbon dioxide, it’s likely a mix of carbonic and sulfuric acids (carbon dioxide and sulfur dioxide dissolved into water) at that time, though technically the water’s pH is on par for a volcanic spring on an inactive volcano and actually rather high (as I understand it, but I’m not a volcanologist). Based on what I know, I find it a stretch that the bodies would have suffered the chemical burns they did, unless they had been stewing for some time (and died of something else, such as a spike in heat or CO2 poisoning), or the pH abruptly dropped, then elevated again (a gas plume of sulfuric acid being the most plausible to me).

    What about the boat melting scene? The characters notice the fish are all dead, suggesting a further drop in pH. Aluminum (what the boat appears to be made of) can be dissolved with acid, and there’s evidence that volcanic lakes can reach an acidity even into negatives. So it’s not a stretch that it would start dissolving the boat, though the speed is questionable. Also, the propellers of the motor dissolve, but not the shaft, because the shaft is likely steel, while cheaper motors use aluminium propellers.

    However, aluminum corrodes easily, and can start severely corroding in as high a pH as about 4, making it a bad choice for use on a volcanic lake too begin with (unless these particular lakes had higher pHs before). The slowest part would be dissolving the protective oxide barrier that aluminum gets. Once that’s gone, the aluminum is soon to follow. The speed at which the boat dissolves is also pretty realistic (albeit probably still a bit dramaticized) when you understand that even common household items like heated baking soda, vinegar, sodium hydroxide (commonly found in drain cleaner), etc can dissolve aluminum fairly quickly, especially if we assume the pH has dropped to somewhere around 1.

    A pH of 1 or 2 would explain the difference in the fish (consider this: digestion takes time even in a carnivore’s stomach which has a pH of 1, so a low enough pH could kill them, but not immediately dissolve them) and the boat (highly reactive below a pH of 4). But what about the humans? That comes back to the individual materials. Ruth’s clothes are relatively thin natural materials, while the coat Paul used was thicker, layered, and water resistant to begin with (the lake is not pure acid, but an aqueous dilution of acids, so waterproofing would require the acidity to first work through it before the liquid as a whole can reach the skin). Odds are good he still suffered some burning, but he bought himself time with the wrapping, and mitigated enough of it to keep going.. Ruth also submersed herself in the water for a good minute or so, giving a large amount of time and surface area for burning and allowing her clothes to soak in it, continuing to burn her even after she was out, while Paul’s paddling limits that somewhat (and he soon has to stop, as the water soaks through).

    tl;dr – the drama of the boat has more to do with the reactivity of aluminum to any acid than the actual acidity of the water.

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