![obduction geology obduction geology](https://perso.univ-rennes1.fr/romain.bousquet/Papers/bouazzer/img/Fig9_c.jpg)
So after that collision, we have the proto-Appalachians. This big duck represents the mountains at the end of that mountain building phase. And that's what we had 300 million years ago with the Appalachians. In fact, as they crashed together, they formed larger and larger mountains that wrinkled up. And when these continents collided, because they're both about the same density, neither one subducted beneath the other.
![obduction geology obduction geology](https://ars.els-cdn.com/content/image/1-s2.0-S1674987115001516-fx1.jpg)
And these are all the ridges and valleys that spread up and down the east coast of North America known as the Appalachian Mountains.Ībout 300 million years ago, North America and what's now Europe and Africa all collided to form a super-continent known as Pangaea. So why are we in a tub with rubber duckies? Imagine that these ducks represent the mountains that surround us right here in Happy Valley. Now, what does all that have to do with rubber duckies, and why am I in the bathtub surrounded by rubber duckies? Well, let's find out. And we're gonna talk a little bit about icebergs. We're going to be talking about how the Appalachians were built, why they're still as high as they are now. Welcome to the GEOSC 10 Tectonics III Section, Mountain Building. When erosion lowers a mountain range, the root floats up, bringing metamorphic rocks to the surface that have been "cooked" by heat and pressure deep within the Earth.īefore we go any further, take a look at the following short video introduction by Dr. Higher mountains have deeper roots (for the same reason that toy boats can float in less water than aircraft carriers, and the iceberg that sank the Titanic stuck farther down in the water than did the ice cubes in the drinks on deck). Nittany near Penn State's University Park campus, and all of the Appalachians were formed by just such a collision when Africa and Europe hit the Americas, causing a long, thin slab of crust to become a short, thick one by folding and thrust-faulting. The answer is obduction, a BIG collision. Old, cold sea floor goes down subduction zones beneath warmer sea floor or continent, but what happens when a high-floating continent or island arc tries to go down a trench under another continent or island arc? Ansel Adams, The Spirit of the Mountains Alley "No matter how sophisticated you may be, a large granite mountain cannot be denied-it speaks in silence to the very core of your being."