Lesson 11: Collisional Mountain Ranges
This week's lesson is our third to explore park landscapes formed at convergent plate boundaries. Unlike our previous lessons on subduction zones, however, this week we'll look at what happens where both of the converging plates carry continental lithosphere and are too buoyant to subduct. Continent-continent collisions have created some of the loftiest mountains on Earth, and give us opportunities to study deep crustal rocks and structures after convergence has spent itself and subsequent uplift and erosion have laid bare the interiors of ancient mountain belts. High mountains also receive abundant precipitation and many are the sources of large rivers, so in this week's exercise you'll learn how geologists measure and report river discharge.
As you read through chapter 6 and browse through the websites below please take careful notes so that you can keep track of major points and recall them more easily when we refer to them later in the semester. Be sure that you are prepared to meet the learning objectives outlined below before you move on to the quiz near the bottom of the page.
Weekly Learning Objectives
Upon successful completion of this week's lesson, a student is expected to be able to:
- Contrast hard and soft continental collisions and brieflly describe what you would look for to distinguish one from another.
- Correctly order the sequence of events that shaped the Appalachian region from the time of the Grenville orogeny to the rifting that opened the Atlantic Ocean.
- Describe the fundamental differences in the origins of the rocks that underlie the Valley and Ridge, Blue Ridge, and Piedmont (+ Coastal Plain basement) of the Appalachians.
- Describe how you could distinguish a gently-dipping thrust fault from a low-angle depositional contact between two rock units of known ages. (Hint: Remember the principle of superposition.)
- Calculate the discharge of a stream using data on its velocity and the cross-sectional area of its channel.
Reading and Browsing Assignment
- Read Chapter 6, focusing on the topics outlined in the learning objectives above.
- Check out the brief description of the geology and geologic history of the Appalachian Highlands given on the U.S Geological Survey-NPS "Geology in the Parks" website.
- To learn more about each of the geologic provinces that comprises the Appalachians simply click on the province that interests you on the interactive geologic map on the Geology of Virginia site from the College of William and Mary.
Exercise 11 (Due by 9:00 AM on Monday, 5-Apr-2010)
Collisional mountain ranges are the sources of some of the world's major rivers and so, to learn more about how geologists measure the amounts of water they carry (their discharges), please point your browser to the Virtual River website. This is the gateway to the two different exercises: River Discharge and River Flooding. Click on River Discharge and work through the exercise to learn how geologists actually measure how much water is moving through a river's channel at a given time. Like Earthquake, the previous Virtual Courseware exercise we worked on, River Discharge uses Java applets and Flash animations—so be patient while they load. When you have completed the exercise, fill in the certificate, right-click on colored part of it to save a copy (not on the white part of the web page around it), and then go to Exercise 11 in the Etudes assignment are send your certificate to me as an attachment.
If you would like, after you're done with River Discharge you can return to the Virtual River page, click on River Flooding, and try that exercise as well. River Discharge is a fairly short assignment (< 1hour) but River Flooding is longer and more challenging. I am not making it a class assignment because there is no supporting discussion about how flood recurrence intervals are calculated in our text.
Quiz 11 (Due by 9:00 AM on Monday, 5-Apr-2010)
After you feel you have met the learning outcomes outlined above, please complete Quiz 11 in the Etudes "Assignments Tasks, and Tests" tool. There are ten questions, each worth one point. If you can answer all of them correctly it means that you know your way around collisional mountain ranges and river discharge pretty well and are ready to move on to learn about parklands formed at transform boundaries next week.