Lesson 8: Ancient Passive Margins
This week's lesson is a continuation of last weeks, but instead of studying modern passive margins we'll explore an ancient one that has been uplifted and deeply incised by erosion on the Colorado Plateau. We'll also consider how the movement of shorelines in response to uplift, subsidence, or sea-level changes affects the sequences of sediments deposited along passive margins.
As you read through the second half of chapter 4 it will be helpful to take 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 this week's quiz. Also, this is the week I will be returning your first outlines and helping you get started on writing an abstract of your first article.
Weekly Learning Objectives
Upon successful completion of this week's lesson, a student is expected to be able to:
- Locate the area where sedimentary rocks deposited on an ancient passive margin are preserved in the western United States, and explain how they are related to North America's past geologic setting and history.
- Order the sequence of major events that are recorded in the rocks of Grand Canyon National Park and neighboring regions of the Colorado Plateau.
- Correctly interpret a continuous of sequence of marine sedimentary rocks (sandstone-shale-limestone) deposited on an ancient passive margin as the product of a marine transgression or regression.
Reading and Browsing Assignment
- Read the second part of Chapter 4, pages 81-86, and focus on the topics outlined in the learning objectives above.
- Browse through the following sites for nice overviews of the geology of the Grand Canyon: Grand Canyon Explorer or Geology of the Grand Canyon Area in Wikipedia. Don't worry about all of the details, just get a sense of what the major events were during the region's history and about when they occurred. (Note: Some of the images on the Grand Canyon Explorer site don't seem to be loading correctly.)
- Finally, check out the page Evidence of Ancient Life that shows fossils in the marine limestones that were deposited on the part of North America's ancient passive margin that lay west of Grand Canyon in what is now the Mojave National Preserve.
Exercise 8 (Due by 9:00 AM on Monday, 8-Mar-2010)
Once you recieve your outline back it will be time to prepare your first abstract. In the left-hand column of this page click on "Documents" and then scroll down and click on "Writing Assignment".
This week we'll be completing step three of the assignment. Working from your outline, write an abstract of your article's major points following the format of the "sample abstract" linked to the writing page. For the purpose of this abstract, act as though you are the author of the article. In this assignment format is very important, and the easiest way to make sure your abstract is formatted correctly is to download the "abstract template" linked to the writing page. Print one copy for reference and then simply "type over" each part of the digital copy on your computer with the appropriate information relevant to your article (title, author information and citation, abstract body, etc.) That way each part of the abstract will be formatted correctly and positioned correctly on the page. (Note that this template is in Word format. If you are using another word processor check the link on the writing assignment page for abstract specifications such as column widths, margins, etc.) When you are done, save your abstract in a place (and with a name) that you'll remember. This is the file you'll send a copy of to me.
The abstract template is a two column document, so if your text in the left-hand column is too long it will "push" the text in the right-hand column down. If this happens, shorten your abstract and remove any blank lines at the top of the right-hand column so that the first line of of text is flush with the title at the top of the left-hand column. Be sure to include your PIN ( last five digits of your Etudes user id) and the course name and date at the appropriate places in the right-hand column. Also, pick three keywords that someone searching for your abstract might be expected to use in a search engine. Proper names (e.g., Mount Shasta) and accepted phrases (e.g., global warming) are okay, but otherwise try to stick to single words. Be sure to only capitalize keywords that are proper names.
Write your abstract in complete sentences and be sure that it is well-organized and coherent. It's a good idea to check out the abstract grading rubric that is also linked to the writing page so that you can see which criteria I will use for evaluation. Complete your abstract and send it to me as an attachment (preferably a Word document) to Exercise 8 in the Etudes "Assignments, Tasks, and Tests" tool by next Monday 8-Mar-2010. I will score your abstract and return it to you with a copy of the grading rubric in about one week. Your abstract is worth twice as many points (20) as a typical weekly exercise, so take your time and work carefully as you write it.
Quiz 8 (Due by 9:00 AM on Monday, 8-Mar-2010)
After you feel you have met the learning outcomes outlined above, please complete Quiz 8 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 North America's ancient passive margin pretty well and are ready to learn about parklands formed at convergent margins next week.