TEKS 8 9 B Relate plate tectonics to

TEKS 8. 9 (B) Relate plate tectonics to the formation of crustal features.

There are three main types of tectonic plate boundaries: convergent, divergent and transform

TYPES OF STRESS THAT CHANGES CRUSTAL FEATURES

STRESS DIRECTIONS Compression Rocks are being squeezed Result is Mountain formations Tension Rocks are being stretched Result is Rift Valley & Sea floor spreading Shear ⇄ Rocks move in opposite directions and are distorted Results faults

Convergent Boundaries Two tectonic plates collide due to compressional forces or stress.

Continent-Continent Convergent Boundary As a result of this boundary folded mountain chains are created such as the Himalaya Mountains. No new crust is formed or created

Ocean-Continent Convergent Boundary The Andes Mountains were created as result of this type of plate boundary. Rising magma forms new crust in the form of mountains and volcanoes Sea Trench rge e nv ate o c r pl n s n w e e i o t o i v d t ea la. H c p ed u z o Melting of d e e b w u u T q S s old crust

Ocean-Ocean Convergent Boundary A deep-ocean trench is a valley on the ocean floor created when an older, denser oceanic plate subducts under a younger, less dense oceanic plate. Volcanic activity is common at this boundary. Aleutian Trench Old crust is melted and recycled.

Divergent Boundary 2 plates move away from one another (“diverge”) due to tensional (pulling) forces or stress.

Divergent Boundary Sea-floor spreading As a result of sea floor spreading new crust is formed and mid ocean ridges develop. Magma rises up and new crust is formed

Divergent Boundary Mid-Atlantic Ridge Indian Ridge

Divergent Boundary

The East African Rift Valley is land that has sunken by divergent boundary

Divergent Boundary Rift Valley in Africa

Transform Boundary two tectonic plates slide past each other due to a shearing force

Transform Boundary Shearing causes faults (weak spots in rocks) and earthquakes. San Andreas fault in California is on a transform boundary.

Transform Boundary