he Plate Tectonics is a theory to explain the observed evidence for large scale motions on the surface of earth's crust.The Plate Tectonics theory surpassed the previous theories of Continental Drift and Sea floor spreading. The tectonic plates are like cracks in the earth's surface. There are 7 major plates and many smaller plates that cover the earth's crust. Figure 1-A shows the plates on the earth and the movement of the plates. If you look at Figure 1-B, you will see the plates movement from Pangaea, to present form. The Tectonic Plates Move at a pace of about 1-2 cm every year. If you look at Figure 1-A, you will see the arrows showing the direction the plates are moving. If you look at the Eurasian plate and the Indian Plate, you will see that they are going towards each other, and subduction is going on there in the northeastern corner of the Indian Plate and subduction is when 2 plates collide and one of the plates goes below the other plate, in this case, in the Indian Plate in going under the Eurasian Plate creating a huge mountain range called the Himalayas. Figure 2-A shows what subduction looks like. When you look at it, you will see that one plate is going down, the part that is going down is the more dense plate of the two plates that are hitting each other. You will also see the volcano, there is commonly volcanoes by subduction zones because of the gap in the land and that is letting magma from the mantle leak through, there for creating a volcano. As the more dense plate goes farther down into the mantle, it will eventually melt, then becoming part of the rock cycle. When plates slide past each other, and example could be the Juan de Fuca plate and the North American Plate. The North American Plate is going southeast and the Juan de Fuca plate is going northwest, so friction will create and earthquake will happen, that is why there is a bunch of earthquakes in California. Where the earthquakes happen, there are plate boundaries form and then there is a fault, a fault is where a bunch of sesimec activity happens. The San Andreas fault is the sliding plate boundary in California. Juan de Fuca plate and the North American plate are the plates that create the San Andreas fault. When the plates move, they don't move in a steady motion, they will stay still for periods of time, then they will start to move.

Figure 1-A


Figure 1-B


Figure 2-A

external image subduction.gif

Figure 3-A

On the picture, you will see the stone from the Juan de Fuca plate and the dirt from the North American Plate, this is part of the San Andreas fault.