9.3 Actions at Plate Boundaries I. Divergent Boundaries A) produces new (crust) B) Rift valleys are deep faulted structures, can develop on the seafloor or on land. C) Oceanic ridges. The rifts at the crest of ridges

9.3 Actions at Plate Boundaries I. Divergent Boundaries 9.3 Actions at Plate Boundaries  D) Continental Rifts • the landmass may split into two or more smaller segments, forming a rift.

East African Rift Valley

9.3 Actions at Plate Boundaries II. Convergent Boundaries 9.3 Actions at Plate Boundaries  A) subduction zones -when 1 oceanic plate is forced down into the mantle beneath a second plate.  B) Types • 1) Oceanic  Continental A) Denser oceanic slab sinks into the asthenosphere. B) Continental volcanic arcs form Ex: include the Andes, Cascades, and the Sierra Nevadas.

Oceanic-Continental Convergent Boundary

9.3 Actions at Plate Boundaries II. Convergent Boundaries 9.3 Actions at Plate Boundaries  2) Oceanic-Oceanic • a) Volcanic island arcs form as volcanoes emerge from the sea. • Ex: Aleutian, Mariana, and Tonga islands.

Oceanic-Oceanic Convergent Boundary

9.3 Actions at Plate Boundaries I. Convergent Boundaries 9.3 Actions at Plate Boundaries  3) Continental-Continental • a) two continents collide. • b) can produce new mountain ranges ex: Himalayas.

Himalayas

Himalayas

Continental-Continental Convergent Boundary

Collision of India and Asia

9.3 Actions at Plate Boundaries III. Transform Fault Boundaries 9.3 Actions at Plate Boundaries  A) plates grind past each other w/out destroying the lithosphere.  B) Transform faults • 1) They aid the movement of oceanic crustal material.