Lesson 16: Transverse Ranges and Continental Borderland

Anacapa Island at sunset, Channel Islands National ParkCalifornia's Transverse Ranges trend roughly east-west and cut across the northwestern alignments of other provinces—such as the Sierra Nevada and Great Valley—that formed in response to Mesozoic subduction. Based on the principle of cross-cutting relationships you would infer that the Transverse Ranges are younger than those Mesozoic provinces, and that's exactly the case. The Transverse Ranges and Continental Borderland developed during late Cenozoic time as movement on the San Andreas fault squeezed and rotated crustal blocks along the western margin of North America. These fault movements have uplifted several large mountain ranges, including those whose summits stick above sea level to form the Channel Islands (Anacapa Island, right) and others whose slopes expose ancient metamorphic and igneous rocks. Movements along the San Andreas have also created deep basins where thousands of meters of sediments have accumulated and entombed tiny marine organisms whose remains produced rich deposits of petroleum and natural gas. The Transverse Ranges province is still very active tectonically, and even though the adjacent San Andreas fault has not produced a large earthquake since 1857 related faults beneath the Los Angeles Basin have taken heavy tolls in lives and property during the 20th century. We'll only have a chance to touch on the diverse geology of this dynamic region this week, but the links below offer additional information if you would like to learn more.

In chapter 16 Harden describes the geologic structures that accomodate compression in the Transverse Ranges, reviews the record of uplift and deposition recorded by the sediments that fill the region's basins, and discusses how block rotations have led to local crustal extension and bimodal volcanism. She also describes the variety of pre-Cenozoic rocks—from the Pelona schist to the Proterozoic crystalline rocks of the San Gabriel and San Bernardino Mountains—that form the "basement" of the province and have been exposed by Cenozoic uplift and erosion. Finally, she explains how petroleum has formed and migrated in to traps within the region, and outlines some of the environmental problems that petroleum extracton has caused. For this week's exercise you'll be writing the abstract of your second article by pulling together what you learned from both your first abstract and your second outline.

As you read about the geology and geologic history of the Transverse Ranges be sure to take careful notes on the topics covered by the learning objectives below. As during previous weeks, you'll find that writing out key facts in your own words or making neatly labeled drawings will help you better understand the significance of what you've read and spot any gaps in your knowledge. Don't hesitate to post any questions you have to the Discussion Board so that your classmates or I can help you figure them out. Having good notes will also make it easier for you to review for this week's quiz and and access what you've learned when you want to refer back to it for future assignments. Be sure that you are prepared to meet the learning objectives outlined below before you move on to the quiz at the bottom of the page.

Weekly Learning Objectives

Upon successful completion of this week's lesson, a student is expected to be able to:

Reading and Browsing Assignment

Exercise 16: Abstract of Second Article (Due by 9:00 AM on 9-May-2011)

Once you recieve your outline back it will be time to prepare your second abstract. To get started, go to the Writing Assignment page.

During week 14 you completed the first two steps of this assignment, and this week we'll be completing step three. 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 (it's a Word document). 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, citation, abstract body, etc.) That way each part of the abstract will be formatted 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 formatting specifications such as column widths, margins and so on.) 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 Assignment page so that you can see what criteria I will use for evaluation. Complete your abstract and send it to me as an attachment in MS Word format to Exercise 16 in the Etudes "Assignments, Tasks, and Tests" tool. 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 16: Transverse Ranges (Due by 9:00 AM on 9-May-2011.)

After you feel you have met the learning outcomes outlined above please complete Quiz 16 in the Etudes "Assignments, Tests, and Surveys" tool. There are ten questions about the California's coast and the processes that are shaping it, and each is worth one point. If you can answer all of them correctly it means that you know your way around the geology of the Transverse Ranges-Continental Borderland province pretty well and are ready to start learning about the Penninsular Ranges next week. Like all of our weekly quizzes, this one is timed (you'll have 30 minutes) and must be completed in one "sitting". (That is, you will only be granted access once.) So, be sure you're ready to complete your quiz when you start it—and be sure you're using Firefox. Good luck.