After seeing the movie, I have to say that its presentation and delivery was more than satisfactory.
Its story, however, is nothing new specially here in the volcano-infested Philippine archipelago. Dante's
Peak is a good adventure/"natural catastrophe" movie that can make the viewers get a feel for how
geologists work. . .

The Movie is set in the Cascade Range of the Pacific Northwest, U.S.A. Dante's Peak is, of course,
not a real Cascade volcano, and although Idaho is adjacent to states with Cascade Volcanoes (Oregon and
Washington), and another state with an active magma chamber there are no Cascade (or any other active or
dormant volcanoes) in Idaho. There is, however, plenty of evidence of past volcanic activity, as there is in
most parts of the world including here in the Philippines.

But before we talk about volcanoes, what is a volcano? Here are some things I learned in my
spine-tingling, exciting and fun-filled class of Nat Sci II!

What is a volcano?

When Volcanoes in the Cascade Range and Alaska erupt, they frequently do so explosively and
produce pyroclastic flows, ash falls and "mud" or debris flows (lahars). According to the USGS, "Lahars
destroyed houses, bridges, and logging trucks during the May 1980 eruption of Mount St. Helens, and have
inundated other valleys around Cascade volcanoes during prehistoric eruptions. Lahars at Nevado del Ruiz
volcano, Colombia, in 1985, killed more than 23,000 people." Near a volcano, the falling volcanic ash is
quite heavy (high density), and the newspaper used as a proxy for volcanic ash in the movie looked more
like snow (low density) as it fell. For geologists who have seen the movie, the hot, runny lava, seen issuing
from the volcano, is the most bothersome issue. Generally, runny, fast-flowing lava (basalt) erupts from
Hawaiian or "shield" volcanoes; but we understand that this makes for a more exciting movie. Lava flows
at Cascade volcanoes are usually thick, and rarely move !
far from the vent (for example Mount St. Helens Dome: see the center photo at the top of this page: the
dome is a mound of rather thick lava that has partially or wholly solidified) unlike the Hawaiian-type flows
and lava fountains shown in Dante's Peak. Stratovolcanoes like the Cascades do not usually produce
pyroclastics and lava in the same eruption. Also, lava is VERY hot (over 1500 F), and most flammable
material (rubber, wood, people) brought near the lava would burst into flame. The radiative heat alone is
sufficient; flammable materials do not even have to touch the lava. We think a car would last only seconds
on a lava flow before it would burst into flames, consuming the occupants. It is worth pointing out here that
lava itself does not burn (most of the constituents of lava are already in their "most oxidized" state), and
what we see burning around lava flows consists mostly of grass, houses. trees, shrubs, animals, etc.

A friend of mine who is also a Geology major noticed that the lake near Grandmother's house becomes
acidic quite fast in the movie, but hey, you need to pack a lot into a movie these days to draw a crowd.
There are very acid lakes around volcanoes and yes, you would not want to swim in them... and yes metal
parts can corrode in acid lakes; a thin metal cable might dissolve on a movie timescale. The acids may be
sulfuric and hydrochloric acid, plus others, and the acidity (roughly measured by how low the pH is) can be
quite high, hundreds to thousands of times as acidic as lemon juice or vinegar, or EVEN Coca Cola! A pH
on the order of 0 to 2 would not be unexpected.

The hot springs in any geothermal area can turn on or off, or change temperature abruptly, but
these changes are usually related to rapid changes in the "underground plumbing" (the system of cracks and
fractures present in underground rock that allows hot or cold underground water to flow from one spot to
another brought about by earthquakes that are usually not directly related to the magmatic activity in the
area). Since most undergound hot water flows through fractures that may be active as faults, changes in the
fracture/fault system during earthquakes can redirect flow, or increase or decrease it.