TYPES OF PLATE BOUNDARIES Chapter 9 Plate Tectonics

TYPES OF PLATE BOUNDARIES Chapter 9: Plate Tectonics

WHEN PLATES COLLIDE • • • A collision between plates creates a convergent boundary Compression pushes the plates together Depending on the type of crust, there are three possibilities: 1. Continental-continental: crust gets pushed upward to form mountains (Himalaya Mountains) 2. Oceanic-oceanic: the more dense oceanic plate is pulled down under the other oceanic plate, creating volcanic islands (or island arcs) and trenches (Aleutian Islands, Japan, Mariana Trench) 3. Continental-oceanic: also called subduction, the more dense oceanic plate is pulled under the less dense continental plate, creating trenches and volcanic mountain ranges along coastlines (Peru-Chile Trench and Andes Mountains)

TYPES OF CONVERGENT BOUNDARIES CONTINENTAL-CONTINENTAL OCEANIC-OCEANIC CONTINENTAL-OCEANIC

DIVERGENT AND TRANSFORM • Where plates move away from one another due to tension, a divergent boundary is created. An example is the Mid-Atlantic Ridge, East Pacific Rise, and Red Sea Rift Zone. • The most common feature at a divergent boundary is a mid-ocean ridge or rift zone. • Where plates move past each other horizontally, a transform boundary is created. • Shearing is the stress that makes the plates move past one another, as seen at the San Andreas Fault in California. Here, the Pacific plate is moving to the northwest past the North American plate. • The movement along transform boundaries is rarely smooth. Instead, there are lots of jerks and jolts along the way. Sometimes, the plates will get stuck for long periods of time and then jerk past each other very suddenly, creating violent earthquakes all along the San Andreas Fault.

DIVERGENT & TRANSFORM

RECAP OF THE BOUNDARIES