Background Material - not part of assignment: The North Cascades site has a HUGE amount of information about geologic time sprinkled throughout, including links to two USGS publications on the subject:
1) "Geologic Time" http://pubs.usgs.gov/gip/geotime/
2) "Fossils, Rocks, and Time" http://pubs.usgs.gov/gip/fossils/

A nice little site which has animations (but is not required reading)  is at: http://www.classzone.com/books/earth_science/terc/content/investigations/es2903/es2903page03.cfm - this starts you at "step 3", and you should continue through and including "step 10".  The rest of the material isn't relevant.

An interesting relative dating exercise that I'm not asking you to do involves the forensics of a murder case and uses material from the above web site.  You might want to look it over.  It can be found at: http://education.usgs.gov/schoolyard/DOWNLOADS/GeoSleuth_TeacherGuide.pdf

Part I: North Cascades

Read the two background pages on geologic time:  http://www.nature.nps.gov/geology/usgsnps/gtime/gtime1.html and http://www.nature.nps.gov/geology/usgsnps/gtime/gtime2.html and then answer the following questions.

1. How old is the Earth?

2. The oldest rocks in the North Cascades Park (there appears to be older rocks outside the park) are approximately 400 million years old.
    a) What era and
    b) What period does 400 million years correspond to.
    c) How much of Earth's geologic history is missing from the North Cascades park?

Go to: http://www.nature.nps.gov/geology/usgsnps/noca/nocageol4.html

3.  Why are the younger volcanic rocks of the North Cascades found primarily in the southern part of this region?

Go to: http://www2.nature.nps.gov/geology/usgsnps/noca/nocageol1.html

4. The North Cascades is a geologic mosaic of what type of materials?

5.  Click on the word terranes.  What is a terrane?

Go to:  http://www2.nature.nps.gov/geology/usgsnps/noca/sb7terorig.html

6.  According to this page, what are the three major settings in which most rocks are born?

7. a) What rocks (sedimentary and igneous) form in the deep ocean?
    b) What rocks represent the metamorphic equivalent of these deep ocean rocks?

8. After metamorphism, are rocks from volcanic arcs easily distinguishable from those weathered off an old continent?

Go to: http://www2.nature.nps.gov/geology/usgsnps/noca/nocageol4a.html

9.  The web site creates the name "domain" for convenience in discussing areas of the North Cascades.
    a) Why do you think the authors divide this region into 3 domains?
    b) Name each of the three domains and give me a brief (few word description of each).
 

Part 2: Relative Dating

There are two geologic cross sections that I would like you to work on.  For each you need to determine the sequence of events - you use a letter associated with a rock layer to indicate the deposition of that layer.  For episodes of folding, tilting, or erosion, you need to actually type the words "folding", "tilting" and "erosion".  You can keep redoing until you get everything correct.

What you need to turn in:  A print out of the page at the point where you quit working on it (it may be completely correct, it may not be if you got tired).  Two exercises means two printed pages.

Exercise 1: http://facweb.bhc.edu/academics/science/harwoodr/Geol101/labs/dating/ - the only problem I had with this was that I could not see the letter "J" in the yellow bricky-textured rock layer, so kept missing it.  For this exercise, you will only use the principles of superposition and cross-cutting.

Exercise 2: http://facweb.bhc.edu/academics/science/harwoodr/Geol101/labs/Dating2/Index.htm - this one is considerably harder than the previous one. For this exercis you will use the principles of superposition, cross-cutting, and inclusions.  Also, where a contact between two layers is slightly wiggly, the author means to indicate the presence of an erosional surface.

Part II  Radiometric Dating

Go to http://www.sciencecourseware.org/VirtualDating/files/1.0_ClocksInRocks.html
 

Work through the site, and print out your certificate at the end. In addition to entering your answers on-line, also type them out in the format provided below.   (Be sure to write down the answers as you work through the exercise).

Half-Life - A Useful Concept:

1. ______

2. ______

3. ______

4. ______

Radioactive Isotopic Decay

1. ______

2. ______

3. ______

4. ______

Parent decay and Daughter Growth Curves:

U-238 ______

Rb-87 ______

C-14   ______

What steps are involved in Rb-Sr dating?
__________________________________________________________
__________________________________________________________
__________________________________________________________
__________________________________________________________

Isochron Diagrams

1. ______

2. ______

3. __________________

4. ________________________________________________________

5. ________________________________________________________

Isochron Diagrams - Rb/Sr - Age in MILLION of years

1. ______

2. ______

3. ______

4. ______

5. ______

Ages of Three Rocks

Granite ________

Gabbro ________

Gneiss _________

Turn in the answers above and ALSO attach your certificate to the end of your homework.