Cascade Mountain Range
The Cascade Mountains are comprised of a series of volcanoes and related volcanic features. On a clear day, flying east or west across the range allows for an incredible view of these snow-capped peaks lined up to the north and south. This volcano chain is the product of the Cascadia Subduction Zone, where the Juan de Fuca plate is being subducted underneath the North American plate.
Log in to BBLearn, go to Module 2, and select the Study Area icon. In the study Area, under Interactive Animations, select the 'Subduction Zones' animation. Use the animation to answer the following questions:
1) How would you characterize andesitic magmas associated with the continental crust compared to the basaltic magmas associated with the oceanic crust?
2) What kind of volcanoes are associated with subduction zones?
3) What island chain in Alaska is an example of a present-day subduction zone island arc?
Log in to BBLearn, go to Module 2, and select the Study Area icon. In the study Area, under Interactive Animations, select the 'Subduction Zones' animation. Use the animation to answer the following questions:
1) How would you characterize andesitic magmas associated with the continental crust compared to the basaltic magmas associated with the oceanic crust?
2) What kind of volcanoes are associated with subduction zones?
3) What island chain in Alaska is an example of a present-day subduction zone island arc?
The Cascades are formed as the Juan de Fuca plate, an oceanic plate comprised primarily of heavier basaltic crust, slides beneath the North American plate. Melting rock deep in the Earth becomes more buoyant magma and rises to the surface. How do you think the rock melts? Where is the heat coming from?
If you aren't sure, bring the palms of your hands together and rub them back and forth vigrously, like you might do on a cold winter day. What force generates the heat in your hands? It's the same force that generates a much greater amount of heat as the two plates rub past each other; enough heat to melt solid rock.
If you aren't sure, bring the palms of your hands together and rub them back and forth vigrously, like you might do on a cold winter day. What force generates the heat in your hands? It's the same force that generates a much greater amount of heat as the two plates rub past each other; enough heat to melt solid rock.
Next to Mt. St. Helens, Mt Rainier is probably the most well-known of the Cascade chain volcanoes thanks to its impressive height (14,410 ft) and its status as a National Park. A view of Mt. Rainier in Google Earth looking northwest (above) reveals evidence of the volcano -- can you see the circular feature at center near the peak in the photo above? That is the currently quiet caldera, filled with snow and ice. Mt. Rainier has erupted many times over the last several thousand years, with minor eruptive activity last recorded in the late 19th century. That is only just over 100 years ago! While most people in the greater Seattle and Puget Sound region worry about the potential for earthquakes, they often don't realize that the greater danger may actually be from Mt. Rainier.
What do you think happens to all of that snow and ice when hot magma rises to the surface and spills out of the volcano? There is much evidence of past mudflows from volcanic eruptions throughout the Puget Sound region, and today hundreds of thousands of people live and work in the areas where mudflows (also called lahars) have happened in the past.
What do you think happens to all of that snow and ice when hot magma rises to the surface and spills out of the volcano? There is much evidence of past mudflows from volcanic eruptions throughout the Puget Sound region, and today hundreds of thousands of people live and work in the areas where mudflows (also called lahars) have happened in the past.