North Cascades Homework

Homework #3: North Cascades - due Wednesday May 16, 2010 - no late labs accepted after Monday May 31. This web site assumes you are familiar with the various types of rocks. Please refer to the chapters on igneous, sedimentary, and metamorphic rocks if you need a refresher. Be aware that in some cases nswers may be found in figure captions.

You were introduced to the three domains in the North Cascades in the previous homework. Now we'll look at some details.

Go to: http://www2.nature.nps.gov/geology/usgsnps/noca/twestdom.html

1. Why are the youngest rocks of the Western Domain beneath the older rocks?

2. How were the lowest rocks exposed?

Go to: http://www2.nature.nps.gov/geology/usgsnps/noca/t1nooksack.html

3. a. What rocks are found in the Nooksack Terrane?
b. In what environment did these rocks form?

Go to: http://www2.nature.nps.gov/geology/usgsnps/noca/sb6sand.html

4. Turbidites (rocks with graded bedding) are often characteristic of a deep marine environment. How did the sand get so far out into the quiet water of the deep ocean?

Go to: http://www2.nature.nps.gov/geology/usgsnps/noca/t2chilliwack.html

5. Finding older rocks on top of youngers ones is a sure sign of what?

6. In what environment did the rocks of this terrane form?

Go to: http://www2.nature.nps.gov/geology/usgsnps/noca/t3bellpass.html

7. I often joke that melange is French for "big mess". What is a melange?

8. What environments are suggested by these rocks?

Go to: http://www2.nature.nps.gov/geology/usgsnps/noca/t4easton.html

9. a. What sort of rocks were the precursors of the Skuksan Greenschist and the Darrington Phyllite?
b. In what environment were these precursor rocks formed?

10. a. What metamorphic conditions are required to produce the unusual minerals found in the Shuksan Greenschist and Darrington Phyllite?
b. In what environment do those conditions usually occur?

Go to: http://www2.nature.nps.gov/geology/usgsnps/noca/tcordom.html

11. All four of the terranes in this domain began as volcanic arcs. In addition, the Chelan Mountains Terrane contains material that did not form in a volcanic arc. In what environment did this material form?

Go to: http://www2.nature.nps.gov/geology/usgsnps/noca/t6nason.html

12. The Nason Terrane consists of metamorphosed sediments. In what environment were those sediments deposited?

Go to: http://www2.nature.nps.gov/geology/usgsnps/noca/t7swakane.html

13. The rocks of the Swakane Terrane are most likely either metamorphosed volcanic rocks or metamorphosed sedimentary rocks from a volcanic arc environment. Why can't they be both?

Go to: http://www2.nature.nps.gov/geology/usgsnps/noca/t8littlejack.html

14. What does the peculiar assemblage of the Little Jack Terrane suggest?

Go to: http://www2.nature.nps.gov/geology/usgsnps/noca/tmethdom.html

15. In general, what does the sequence of rocks in the Methow domain represent?

Go to: http://www2.nature.nps.gov/geology/usgsnps/noca/t9hozomeen.html

16. How can you tell that some of the basalt of the Hozomeen Terrane erupted underwater?

Go to: http://www2.nature.nps.gov/geology/usgsnps/noca/t10methow.html

17. What has helped geologists establish the history of the Methow Ocean?

Go to: http://www2.nature.nps.gov/geology/usgsnps/noca/nocageol6.html

18. Where were the rocks of the Metamorphic Core Domain metamorphosed?

19. What do stitching plutons that intrude many terranes show geologists?

20. When were many of the stitching plutons emplaced?