1. California Geologic History
Simplified and related to the Monterey Bay and Canyon Formation
Part 1

2. 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.

3. The earth’s solid surface (crust) is active and broken into pieces called plates, which slide slowly over the soft layer (Asthenosphere)

4. Plates Current plates and boundaries
Volcanoes occur mostly where one plate is going under another – subduction zones – especially the ring of fire around the pacific ocean. Places where the plates are separating include the mid Atlantic ridge

5. Types of Plate Boundary
Point out the details in the subduction areas with volcanoes above the descending plate as this created much of Ca
And the oceanic spreading ridge which created seamounts like the Davidson

6. Ca Geology Extremely complex
Only a few fragments of rocks older than 500 million years
Students should have a print out of this for each table
Point out the Monterey Bay area , the Sierras and the many “slices”

7. 500 million years ago
California, Oregon and Washington were still ocean
Quickly show this one

8. 3 D illustration of island arc formation

9. 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.
Show granite sample and have students find the small ones in their boxes

10. California stages Spend plenty of time on this slide
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
Spend plenty of time on this slide
Point out the succession of added slices, the gradual growth of the Sierras

11. Evidence
The slices which were pushed onto Ca contained special deep mantle rocks rarely found on land.
These are purple on this map
Return to this and point out the slices and thin layers of PURPLE rock

12. 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
The spreading zones are where arrows are shown in opposite directions. There are several not too far off shore.
The Davidson seamount is part of the Marine sanctuary.
Do cut and paste activity before proceeding to part 2