Plate Boundaries Earth’s crust plus the upper mantle forms the lithosphere. Earth’s lithosphere is broken in a number of different pieces. How these pieces move and interact is what plate tectonics is all about.

Convergent boundaries When 2 plates collide with one another.

Convergent boundaries When oceanic plates collide, one subducts under the other. This forms a valley in the ocean floor called a trench.

An example of a trench is the Marianas Trench.

Convergent boundaries When continental plates collide mountains form.

Convergent boundaries What happens if an oceanic plate and a continental plate collide? Which plate would subduct? The oceanic plate must subduct under the continental plate. A continental plate is simply too buoyant to subduct under an oceanic plate.

Divergent boundaries A divergent boundary is the line between two plates where they are moving apart.

Divergent boundaries Divergent boundaries can be found on continents as rift valleys. When a rift valley forms on land, it may eventually split the landmass.

Divergent boundaries Divergent boundaries can also be found in the ocean Sea floor spreading occurs at a mid ocean ridge.

Plate boundaries An edge of a lithospheric plate that slides by another plate is called a transform fault boundary.

Transform fault boundaries When seen from above, the feature will appear to make a zig- zag. Causes Earthquakes San Andreas Fault

Earth’s lithospheric plates Can you identify the three types of plate boundaries labeled A, B, and C?.