Introduction
Ascending eruption cloud from Redoubt Volcano near Cook Inlet, Alaska
in April, 1990. (Photo: J. Warren, USGS.) When people think of geology, they often immediately think of volcanoes. Volcanoes, along with earthquakes, let us know that the Earth is "alive" and that its landscape is slowly changing over time. As you learned earlier, volcanic activity is connected to plate tectonics. But, oftentimes, when people think of volcanoes, we often imagine a clan of cartoonish “natives” worshiping a fiery pit of hot molten rock (e.g., “Indiana Jones and the Temple of Doom”) or the Southpark version where an active volcano seems to exist in geologically improbable places (and even if a cone volcano did exist in the Rocky Mountains of Colorado, it wouldn’t erupt like it shows in the episode!)
In this section, you will where to find volcanoes and how they work. The geology of Tolkien’s Middle Earth aside, we will learn that volcanoes can only exist in specific tectonic settings and that these tectonic settings result in very different types of volcanoes.
From volcanoes that look like huge craters to volcanoes that look like a perfect isosceles triangles, from volcanoes that spew rocks and ash to volcanoes that have gently flowing lava, we’ll learn that the tectonic settings which create these different types of volcanoes can tell us why they erupt the way they do.
Equipped with this information, you will learn the types of volcanoes and their associated volcanic activity. We’ll also take a look at few examples. Once you know how they work, you can understand why Alaska has many volcanoes whereas the Rocky Mountains haven’t seen a volcanic eruption in over 24 million years – sorry Southpark!
(The links on this page are not required reading.)