Plate Boundaries Plate Tectonics Plate Tectonics the theory that the Earths lithosphere is divided into tectonic plates that move around on top of the asthenosphere The lithosphere is made of two types of crust Continental Less dense, Thicker on average Oceanic More dense, Thinner on average What Directions Do Plates Move? 3 types of plate boundaries 1. Convergent Plates are moving towards each other 2. Divergent Plates are moving away from each other 3. Transform Plates are moving past each other Convergent Plates are moving towards each other Subduction subduction occurs when one tectonic plate is pushed underneath another DENSITY!! More dense plates will sink below less dense plates Convergent Plate Boundary Arrows Picture Land Features Trenches, Island Arc, Underwater Volcanoes Oceanic-Oceanic Ocean-Continent Arrows Picture Land Features Very active volcanoes, Trench from subduction zone Continent-Continent Arrows Picture Land Features Mountain Ranges Divergent Plate Boundary Divergent Plates are moving away from each other Sea-floor Spreading at divergent boundaries magma rises and cools, slowly pushing the plates apart Where the magma comes up is called an Oceanic Ridge Transform Plate Boundary Transform Plates are moving past each other Strike-Slip-Fault Plates are moving past each other causing friction and earthquakes Famous Example San Andreas Fault