Dantes Peak
...Mt. Jefferson, and most notably Mt. St. Helens. The range spans from Northern California to Canada. The sign in the movie suggests that the city is located to the east of Seattle in Washington. In relation to the Cascade Range, this is very believable. It could be a real place. The volcano depicted is a stratovolcano, the very type of many Cascades volcanoes. Hot springs are also very common surrounding volcanoes, both recently active and not. In fact, they are a “manifestation of volcanic activity” resulting from interaction with magma or igneous rocks (Encyclopaedia Brittannica 1994). The fast change in temperature by way of magma shooting through the bottom is incorrect. Temperature changes do occur, but usually more slowly and not in a matter of seconds. The magma is probably just a little extra Hollywood glitz. The location with the hot springs, however, is altogether very plausible. Before the eruption, the geologists use many techniques and devices to decide if the volcano is likely to erupt. They talk about issuing warnings to the towns if the results show an eruption to be likely and they monitor volcanic activity from a home base of sorts. All this is based in fact. In the movie it all sounded very reliable and scientific. Most of it is true. When Paul promises to monitor the volcano very carefully, he says they will use every method available. The methods he lists are seismometers, tiltmeters, monitering gas emissions, laser beams, and a robot. The seismometer is used to gauge the magnitude of tremors. It really is a useful device because shallow earthquakes around the volcano are often triggered by a build-up of steam, water, or magma. This was the case at Mt. St. Helens. The tiltmeter, another important instrument, monitors ground deformation. Often, rising magma pushes the volcano “up and out, like a balloon filling with air” (Technology Review 1996). The tiltmeter would record the slightest changes to the volcano and assist in predicting any eruption. Reading gas emissions is also instrumental in predicting an eruption. These emissions are so tell-tale because the denote the upward movement of magma. When magma is deep beneath the surface, pressure keeps the gasses dissolved into the magma. As it rises, however, and pressure subsides, the gasses are released. In 1991 at Mt. Pinatubo, the volcano the geologists draw comparison to in the movie, the unprecedented levels of sulfur dioxide helped make the prediction of eruption possible that saved thousands of lives. Increased gas emissions can have many consequences. Dante’s Peak depicts dying trees and wildlife as a result of increased carbon dioxide. This does happen. The carbon dioxide gets into the soil and low areas, killing trees by the roots and suffocating ground dwelling animals like the squirrels in the movie. In the movie, they check for sulfur dioxide levels and find everything to be fine. They use Cospec readings to figure this out. This follows with fact. Although not mentioned in the movie, the European Space Agency launched a satellite, Envisat, which could detect the presence of volcanic gasses. Perhaps in the future this satellite will be very useful in predicting eruptions. Other methods not mentioned in Dante’s Peak include geological studies of past volcanic activity and checking for gravity changes. The movie suggests that laser beams are bounced off the volcano to check for changes in size. This is a bit far-fetched. The robot that the geologists send into the volcano’s crater to “take its temperature” also doesn’t exist. In reality, temperature changes can be an indication of an impending eruption. Robots do not measure these changes, however. Dante’s Peak does a very good job of capturing the catastrophic nature of a volcanic eruption, and sometimes too good of a job. Earthquakes, lahars, pyroclastic clouds, and lava flows do all result from volcanic eruptions. Seismic activity does occur in connection with volcanic activity, hence the seismometer. At Mt. St. Helens in 1980, 47 earthquakes of magnitude 3 or greater occurred within a 12 -hour period ( Encyclopaedia Brittannica 1994). Just before the big earthquake in Dante’s Peak, just such a quake swarm was going on with each quake having a magnitude of about 3. The largest earthquake at Mt. St. Helens and most other volcanoes was right around 5.0 magnitude. This is where the movie becomes unbelievable. The earthquake that occurs during the town meeting topples telephone poles and church steeples, collapses a freeway, and destroys buildings. The earthquakes typical of volcanic activity, however, causes only “very local minor damage”, not in complete destruction as the movie would have you believe (Encyclopedia Americana 1998). Two of the most destructive hazards of volcanic eruption are lahars and pyroclastic flows. Lahars are “a mass movement feature on the flank of a volcanic cone” (Encyclopaedic Dictionary of Physical Geography 1985). They can be wet or dry, moving “either as a mudslide when saturated with water or as a dry landslide as a result of earth tremors”( Encyclopaedic Dictionary of Physical Geography 1985). The lahar depicted in the movie is wet and appears as a cascading mudslide and flood that sweeps Paul away. This lahar would be composed of rock, debris, ash, and water. When hot lava meets snow, the result is this lahar that can move down a mountain as fast as 60 mph. Pyroclastic flows are more dangerous still. They are a “fluidized emulsion of volcanic particles, eruption gasses, and entrapped air”. Pyroclastic flows have a “low enough viscosity to be very mobile and high enough density to hug the ground” (Encyclopaedia Brittannica 1994). The “pyroclastic cloud”, as Harry calls it, in Dante’s Peak is a fairly accurate representation of destructive power. Typical pyroclastic flows, however, have a temperature that ranges from 100 degrees to 700 degrees Celsius and moves at several kilometers per minute. It would obliterate and incinerate every thing in its path. Though in the movie it gets the obliterates very right, a little incinerate is missing. Also, the heroic truck in Dante’s Peak would not have been able to outrun the flow, even if it were going at top speed....