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California Geologic History Simplified and related to the Monterey Bay and Canyon Formation Part 1 Introduction The earth is very old – 4.5 billion years old Most of California of relatively new The mountains are still changing, and most features are very young (geologically)—only a few million years old. The earth’s solid surface (crust) is active and broken into pieces called plates, which slide slowly over the soft layer (Asthenosphere) Plates Current plates and boundaries Types of Plate Boundary Ca Geology Extremely complex Only a few fragments of rocks older than 500 million years 500 million years ago California, Oregon and Washington were still ocean Dinosaur Era 245-65 mya (Mesozoic) The Sierra Nevada Mountains were pushed up (uplifted) by the formation of the granitic rocks underground The ocean plate continues to push under North America adding a series of slices of old sea floor to the land. California stages 170 mya - no central valley or coast range 130 mya - central valley is a sea, and coast ranges are starting 40 mya - central valley is dry. Coast ranges bigger and higher Evidence The slices which were pushed onto Ca contained special deep mantle rocks rarely found on land. These are purple on this map By 100 Million years ago the spreading centers off the Ca coast were getting closer to the subduction zone. The spreading centers formed a series of underwater mountains including the Davidson Seamount