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.
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.
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
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.