10 March 2012

Learning moments in geology movies

Posted by Jessica Ball

Between digging into fluid dynamics papers, figuring out stability fields for alteration minerals and generally dealing with being a grad student, I haven’t had a lot of time to post lately. (Plus I had to do my taxes this weekend…) But I did get great comments on the “Survival Geology” post, especially about using movies and TV to teach science, and I thought I’d run with some thoughts on those.

It’s pretty easy to nitpick a movie or TV show for science mistakes, but it’s an interesting challenge to turn the nitpicking into an opportunity to learn instead. Instead of saying, “That’s wrong!”, it’s ultimately much more satisfying to say, “How could it work in the real world – and if not, why?” One example that stands out in my mind was a paleontology lab I did in undergrad after we watched Jurassic Park. The scene where our heroes are chased (in their Jeep) by a cranky Tyrannosaurus brought up a few questions while we were watching it – namely, “Are you really telling me they couldn’t outrun that thing?” So our professor had us do a lab to calculate, based on what we knew about T-Rex physiology, what the dinosaur’s top speed actually was. (If I’m remembering right, it was around 25 mph, so it might have been a much shorter chase scene. I can just imagine the T-Rex standing there going “screw this, I’m going to go eat something slower.”)

So here are a few of my favorite geology movies, and potential “learning moments” that we could draw from them.

The Core

There are a lot of things about this movie that make me cringe (other people have covered them extensively), but I think my favorite moment is early on when Dr. Keyes is describing the function of Earth’s geomagnetic field using a peach and a homemade flamethrower. I wish I could find a way to do a demo like this someday, because demos can be an effective way of communicating a concept (especially if they’re flashy or explosive). Without our magnetic field, we might not necessarily burst into flame, but we would be exposed to cosmic rays and ultraviolet radiation that would certainly cause some problems. Solar weather (like the big storm that’s going on right now) would probably do more damage than it does now. And using a peach to represent the Earth is actually not a bad example: a peach has a very thin skin compared to its innards, just like the Earth’s crust and mantle, and the peach pit comes close to being the size of the core, if you have a smallish peach. (The analogy stops there, however, since the outer core isn’t solid.)

Dante’s Peak

For the most part, this isn’t a bad depiction of an explosive volcanic eruption, albeit one that occurs on an accelerated timescale. (There are even lahars!) But one big sticking point is the arrival of Hawaiian lava flows on a Cascades volcano. Now, this is something you’re not likely to see happening over the course of one eruption. But there are conditions under which you can get explosive eruptions and lava flows at the same volcano over the course of many eruptions.

"Gareloi Volcano, elevation 1573 m, in the western Aleutian Islands, Alaska. Levied lava flows from a 1980s eruption drape the south flank of the southern summit crater. The white zone on the crater headwall is an extensive fumarole field." From the Alaska Volcano Observatory website, http://www.avo.alaska.edu/images/image.php?id=1992. The summit craters produced explosive eruptions in 1929, and the lava flows were erupted between 1949 and 1980.

How, you ask? Well, there are a number of factors, but most of them center on the magma fueling the eruption, and its viscosity. Viscous magmas tend to contain lots of volatiles (gases like water vapor and carbon dioxide); more phenocrysts or a higher silica content also make the magma “stickier”. Temperature can play a part as well, and magma with a higher silica content also tends to be cooler and has a harder time flowing. So if a volcano erupts different batches of magma with variations in these factors, the eruption will behave differently. The differences could be due to magma having more time to cool and crystallize in a magma chamber, or it could be that a new, hot magma of a different composition was introduced to the reservoir. It’s possible for magma to evolve during the course of an eruption, but usually not on the scale of hours – so you’re not going to get simultaneous explosive and effusive activity like Dante’s Peak portrays.


Image from http://imcdb.org/vehicle_161312-Ford-Aspire-1994.html

There are a couple of lessons to learn from this one. The first concerns the (lack of) connection between volcanic eruptions and tar pits. The La Brea Tar Pits featured in the movie are formed from petroleum released from the oil-bearing mudstones of the Miocene Monterey formation, at the bottom of a series of marine and fluvial deposits – not exactly volcanic material. In fact, the closest volcanoes to Los Angeles are in the Coso volcanic field, over 100 miles away (and they haven’t been active in the last 10,000 years). There are certainly a lot of faults in the Los Angeles area – and we know that faults can provide pathways for magma in volcanic eruptions – but that does require actual magma. If there were magma under Los Angeles…well, that would be another story! (And another excellent geologic reason not to live there.)

The interaction between Anne Heche as our heroic geologist and Tommy Lee Jones as our even-more-heroic Office of Emergency Management official is the second thing that I find merits discussion. The role of volcanologists in dealing with eruption monitoring and hazard mitigation is a tricky one. Things can get messy in an organizational and legal sense when scientists double as decision-makers in hazard mitigation situations, so what happens is that scientists take the responsibility of informing civil authorities about the hazards, but leave the decision-making to the crisis managers. It’s our responsibility to make sure the crisis managers are adequately educated about the dangers and possible repercussions of a particular situation, but we tend to stay in the background when it comes to calling the shots. The USGS’s Volcano Disaster Assistance Program is a prime example of this – their volcanologists will help set up monitoring equipment and develop hazard assessments, but they don’t call the shots.

Journey to the Center of the Earth (new)

This movie does require some major suspension of belief. But when I was working at AGI before going to grad school, we were actually asked to help create an educator’s booklet to be used along with the movie, and that required me to look for topics that we could turn into lessons.

A few that made it into the booklet are:

  • Plate tectonics – Brendan Fraser’s character is a seismologist who runs a “Center for Plate Tectonics” at his university. The visual highlight of the Center is, of course, the nifty computer displays that show seismic activity around the world.
  • Rock types – Our heroes start off their journey in Iceland, where we get to see lots and lots of lovely volcanic rocks. But when they enter an abandoned mine and begin descending into the Earth, they start seeing other rock types (including a few notable minerals like feldspar and muscovite). So we added a section about different rock types and where they form (although because the booklet was drawn in comic-book style, the sedimentary rock kind of looks like a potato, but it is pretty hard to draw a cartoon of a rock).
  • Earth structure – “What’s really in the center of the Earth?” is the question posed here, because I think everyone who watches this movie has some idea that it’s probably not hollow and full of dinosaurs. So there’s a basic cutaway diagram accompanied by a little description of how we know what the structure is (seismology, geochemistry, etc etc.)

I really liked that the people making the movie wanted to help teach as well as entertain, and I think the booklet was a great compromise between the movie’s fantasy world and our real one. (You can still download a PDF from AGI here.)

It’s a balance that’s tricky to strike. As I mentioned before, it’s really easy to spend all your time complaining about what’s wrong in movies and TV, but it takes much more time and effort to use those mistakes as an opportunity to learn about what’s actually right. (It took me several days just to come up with the discussion in this post, and I’m familiar with the movies and the science!) I’d really like to see more entertainers taking the route that Walden Media did with Journey, and invite the experts to help make the science better. We’d love to help!