- Cascadian Background -
0:06:20 - The location for the movie is a mountain in the Cascade range
monitored by the Cascades Volcano Observatory, specifically, a mountain in the state of Washington. The reason this region has so many volcanoes including Mount St Helens and Mt Rainier is due to the plate tectonics of the region. I will go into this more in the plate tectonics section of the website (under construction) but for now this region is volcanic because of the proximity of a subduction zone. Simply put, this is where one plate goes beneath another plate and starts to melt. The melted rock then rises in the earth and forms the volcanoes (bottom picture to the right).
This type of area along continental edges forms volcanoes with explosive capabilities called "stratovolcanoes." This type of volcano produces the variety of eruption seen in the movie by Dante's Peak (the volcano). The reason the volcanoes are explosive is because of the type of magma that is erupting. Looking at the igneous rocks part of the website you can see there are 3 main types of rocks based on silica content. The less silica in the rock the more "mafic" it is and the hotter the rock is when it erupts. This magma is more common in volcanoes like Hawaii. The magma erupting in the Cascades has a higher silica content (felsic) causing it to cool faster, which results in an eruption consisting of more gaseous and solid material (San Diego State University Geology Department).
We will go in to the type and order of the eruption that is presented in more detail below, but just so you know we are basing this on the typical eruption of the area.
Also so you know the Cascades Volcano Observatory is a real place which was developed following the eruption of Mount St Helens, although it is located in Vancouver not Portland as mentioned.