Tearing Down Mountains: Weathering, Mass Movement, & Landslides
This is Spring Creek. We're in the Spring Creek Canyon just downstream from Penn State's University Park Campus. People have been coming here to Fisherman's Paradise for a century almost, to catch wild brown trout in this world famous trout stream. The creek once flowed way above our heads, way up there, and it has cut this canyon and left these glorious 200 foot high cliffs here.
Right next to me there is a big rock and that big rock used to be at the top of the cliff and it fell down. If you have a kitten and you put something on a table or a shelf, the kitten tends to knock it off. There aren't kittens up there knocking down the rocks but there are ice crystals growing in cracks that widen the cracks. And there are tree roots growing in the cracks, and there are little earthquakes shaking things. The weather attacks the rocks. It breaks them up, things get in the cracks, and they knock them down. Once it gets down here, the stream may break it up more. The stream eventually will pick it up and take it down to the Chesapeake - to the ocean. And then sometimes the rocks dissolve on the way and there are things we can't see in the water that get taken down to the ocean, and they get made into seashells down there. And the pieces, and the seashells, eventually may get scrunched in an abduction zone or taken down a subduction zone to feed volcanoes, to make new rocks that can be attacked by the weather again. And if you see a cycle here, it's because there is a cycle.
We will tell you later how we know the times. The fastest this cycle can run is about 10 million years. Right here, these rocks are about 500 million years old so it's been a pretty slow cycle here, but pieces of it can be fast, because if you're in the way when that rock falls down it could kill you in a second. So there's very interesting things we have to understand here and we're going to deal with them in this module.
Fans of old-fogey rock music may recall that Paul Simon was "slip-sliding away." Paul was singing about human relations, not about debris flows. But, our hillsides really are “slip-sliding away,” too. Weather attacks rocks to make loose blocks, which may fall off cliffs rapidly or hang around to make soil before sliding downhill. So, crank up the tunes, watch out for rolling boulders, and let’s slip on into Module 5.
Learning Objectives
- Explain why the wind blows.
- Discuss why wind going up mountains produces rain and then becomes warmer going down the other side.
- Explain how weathering changes rocks physically and chemically at the Earth’s surface.
- Discuss mass movement and the downhill motion of loose rocks and soil.
- Explain how weathering and mass movement of old rocks are part of a cycle that leads to new rocks that experience weathering and mass movement.
What to do for Module 5?
You will have one week to complete Module 5. See the course calendar in Canvas for specific due dates.
- Take the RockOn #5 Quiz
- Take the StudentsSpeak #6 Survey
- Submit Exercise #2
- Begin working on Exercise #3
Questions?
If you have any questions, please feel free to send an email through Canvas. Remember to include all of the teachers and all of the TAs in the "To" line. Failure to email all teachers and all TAs may result in a delayed or missed response. Directions for how to send an email can be found in the Resources module.