Tectonics

Tectonics

The changing shape of a planet's surface because of forces from inside.

Stress

A force that pushes, pulls, or squeezes rocks.

Fault

A crack in rock where the rocks move past each other.

Brittle deformation

When rocks break instead of bending.

Ductile deformation

When rocks bend, stretch, or flow without breaking.

Plate tectonics

The movement of large pieces of a planet's outer rocky layer.

Normal faults

Caused by extension, which pulls rocks apart.

Thrust or reverse faults

Caused by compression, which squeezes rocks together.

Strike-slip faults

Caused by shear, which makes rocks slide sideways past each other.

Graben

A lowered block of land formed when the surface is pulled apart.

Rift

A long area where the surface is pulling apart.

Effects of a rift opening

It can eventually become an ocean.

Thrust faults and mountains

They push and stack rocks together, making the land higher.

Subduction zone

A place where denser oceanic rock sinks underneath less dense material.

Rocks folding instead of breaking

Caused by warm temperatures, high fluid pressure, or slow forces.