Types of Plate Boundaries After completing this section, students will identify that the Earth is made of geologic plates (Standard PI-041) and investigate the types of plate boundaries (Standard PI – 043)

According to geologists, the Earth’s crust is broken into moving sections called plates. The plates move toward each other, move away from each other, or move past each other

Scientists classify plate boundaries according to how they move. There are three types of plate boundaries Divergent Boundaries Convergent Boundaries Transform Boundaries

Divergent Boundaries

Divergent boundary – boundary between two plates that are moving apart Also known as spreading centers

Most divergent boundaries lie along the ocean floor and have rift valleys Rift valley – deep valley at the center of a mid-ocean ridge

Molten rock forces its way upward through cracks along the valley The molten rock cools and forms new sea floor

Convergent Boundaries

Convergent boundaries are boundaries between 2 plates that are moving toward each other There are 2 classifications of convergent boundaries: subduction zones and collision boundaries

Subduction zones occur when an oceanic plate slides beneath another plate Deep-sea trenches form at these boundaries, as well as chains of volcanic islands

Subduction can also occur between an oceanic and a continental plate Mountain chains and volcanoes form at these boundaries

Collision boundaries forms when 2 continental plates collide Mountains ridges form at these boundaries, like the Himalayas

Transform Boundaries

Transform boundaries occur when 2 plates slide past each other The San Andreas Fault is an example of a transform boundary