240PreLab04CAFaults - EXERCISE#4 PRELAB revised summer08 OK...

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Color Fig. 1a. Satellite image of California. From: http://www.ss.ca.gov/museum/map/spring.jpg Fig. 1b. Major provinces of California. From: California Geology, 1998, by D.R. Harden. EXERCISE # 4 PRELAB revised summer’08 OK GEOLOGY 240 Week of Sept. 29 – Oct. 3, 2008 EXPLORING MAJOR ACTIVE FAULTS IN CALIFORNIA INTRODUCTION California has some very distinctive features – mountains, valleys, deserts, and numerous faults . Can you see a correlation between the color satellite image and the major provinces illustrated in Fig. 1b? For example, how might you recognize the Mojave Desert province on the color satellite image? Can you delineate two major faults that border the Mojave? In lab this week, you will be examining topographic and geomorphic features associated with faults, and plotting some major faults on a road map. To understand the natural diversity of California (and the major provinces), let’s begin with a brief overview of the geologic history, beginning in the Mesozoic Era. 1 of 8
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PART I. A BRIEF GEOLOGIC HISTORY From: http://www.sonoma.edu/users/f/freidel/california/390geology.htm About 200 million years ago, in early Mesozoic time, Pangaea began to break up, creating the North American plate as we see it today. Between 100 and 50 million years ago the North American plate moved westward, breaking away from what is today the European continent. Approximately where today we see the Sierra Nevada Mts ., (see Fig. 1b.) a subduction zone formed off the west coast of the North American plate. This subduction zone resulted in the collision and accretion of belts of oceanic rock that gradually built the continental margin westward. During the Mesozoic subduction, magma rose up from beneath the descending plates, causing the formation of chains of andesitic volcanoes at the surface and plutons of granitic magma beneath them. Plutonic rocks from this period are found in the Klamath Mountains , Sierra Nevada , Basin and Range , Mojave Desert and Peninsular Ranges (see Fig. 1b.) During this time the Farallon plate was subducted and consumed beneath the North American Plate. By 100 million years ago the subduction zone had shifted westward to the approximate position of today's Coast Ranges (Fig. 3). Portions of the Farallon plate, along with
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This note was uploaded on 10/06/2008 for the course GEOL 240 taught by Professor Sammis during the Fall '08 term at USC.

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240PreLab04CAFaults - EXERCISE#4 PRELAB revised summer08 OK...

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