Main Menu

1. Whole Lotta Shakin' Goin' On

Expedition Menu

1. Introduction

2. Global Distribution

3.  Earthquakes & Plate Boundaries

4. The Ring of Fire

5. Convergent Boundaries

6. Atlantic Ocean

7. Atlantic Ocean II

8. Alaska Earthquake

9. Vertical Slice

10. 3-D Look

11. California Plate Boundaries

12. Are You Prepared?

13. Mendocino Triple Junction

14. Could It Happen Here?

hand pointerDownload Expedition Worksheet,
if you do not have course workbook

Objectives: Students will learn about the global distribution of earthquakes and volcanoes in both space and time, which is central to our understanding of plate tectonics, the formation of the seafloor, movement of the plates of lithosphere, and interactions at the boundaries between plates.  The movement of the seafloor, resulting from underwater earthquakes poses a significant threat to communities along coastal California.

This expedition serves as a good review of the material in some of the previous expeditions while the concepts presented in the following web pages are closely related to the dangers posed by undersea earthquakes and tsunamis, which will discuss in the next expedition.

Make sure that you read the accompanying worksheet as it also contains important information on this subject.

The screens that follow will show the distribution of the surface locations of earthquakes, or epicenters.   We will see that most of these earthquakes are located along the location of plate boundaries, mainly under the sea or along the coast.   

Earthquakes occur within the Earth down to a depth of 670 kilometers, in other words in the crust or upper mantle. In fact, earthquakes only occur in the lithosphere, the rigid outer layer of the earth that composes the tectonic plates. The diagram at the right, and in your worksheet, shows how the location of an earthquake within the earth is projected upwards, towards the Earth surface, to determine the location of the epicenter.


Don's Introduction
I am here above Stinson Beach where the San Andreas fault comes on onshore in the background at Bolinas Lagoon. The San Andreas fault is one of the majpr sources of devastating earthquakes along California. In this expedition we will look at the distribution of earthquakes, both on the surface of the earth and at depth to see how these earthquakes define the locations of the plate boundaries.

We will look at the earthquake distribution beneath the Pacific and Atlantic Oceans, up near Alaska, including the great Alaska earthquake of 1964, and finally along coastal California to look at the major plate boundaries. We will look at the transform plate boundary along much of California that extends northward to the boundary between three plates, called a triple junction, near Cape Mendocino. We will look at a small plate, the Gorda plate, in this region which is being deformed and not acting as a rigid plate.

Theis expedition provides a transiton between plate tections and hazards to society posed by undersea earthquakes and tsunamis.

Contact Don Reed
Dept. of Geology
San José State University
©Copyright 2007
Last Updated on
September 24, 2007

Let's examine the distribution of earthquakes
over the past 50 years