Three ways plates meet

A plate boundary is where neighboring tectonic plates interact. The three basic types describe their relative motion. Real boundaries may combine motions or spread deformation across a network of faults.

Conceptual diagrams, not to scale. Divergent and convergent views are cross sections; transform is viewed from above.

Divergent: making room for new crust

Plates move apart, and material rises into the opening. At oceanic spreading ridges, magma cools to form new oceanic crust. The Mid-Atlantic Ridge is an example. Divergence also occurs in continental rift zones.

Convergent: collision and subduction

Plates move toward one another. An oceanic plate may descend beneath another plate at a subduction zone, such as along the west coast of South America. When continents collide, the crust can thicken and form mountains, as in the Himalayas.

Transform: sliding along the boundary

Plates move sideways past each other. The San Andreas Fault system is a familiar example. Friction can prevent smooth motion; accumulated strain is released when a fault slips in an earthquake.

A plate boundary is bigger than a fault line

A plate boundary describes how large regions of the lithosphere move relative to one another. A fault is a fracture or zone where rock has moved. A single boundary can contain many faults, and faults can also occur within plates.

In Explorer, the boundary overlay shows the global arrangement. It is not a detailed inventory of every local fault, and its line color does not distinguish the three boundary types. Pair the map with these examples to interpret what you see.