Plate Boundaries PDF

# Plate Boundaries **Cut and paste the pictures and statements below into your books under the following headings: Divergent, Convergent and Transform.** ## Divergent Plate Boundaries - This often creates a zone with many volcanoes and earthquakes. - Leads to subduction zones where the sea floor...

# Plate Boundaries **Cut and paste the pictures and statements below into your books under the following headings: Divergent, Convergent and Transform.** ## Divergent Plate Boundaries - This often creates a zone with many volcanoes and earthquakes. - Leads to subduction zones where the sea floor (oceanic crust), which is very dense pushes under the lighter continental crust. - Also known as constructive or extensional plate boundaries. - New crust is generated e.g. the mid-Atlantic Rift. Upwelling magma is ejected at the surface. As the newly-formed basalt cools, it adds to the plates. ## Convergent Plate Boundaries - When tectonic plates slide and grind against each other. - May lead to the formation of mountains either by physically pushing up the continental crust or by the melting and buoyant rise of less dense rock material generated during subduction. - Most are locked in tension before suddenly releasing, sliding and causing earthquakes. - Subduction zones are also being considered as possible disposal sites for nuclear waste, where the action would carry the material into the planetary mantle. - Rock closest to the boundary is younger than rock further away on the same plate. - The Southern Alps rise dramatically beside the Alpine Fault on New Zealand's West Coast. - Initially produce rifts which produce rift valleys if occur on continents. - Convection in the mantle causes material to rise to the base of the plate boundary, supplying heat & reducing pressure that melts rock beneath the rift area, filling the gap left when they part. - Where two plates move towards each other. - Also called destructive plate boundaries. - Continental collisions in which the colliding plate material is of similar density may also cause mountain-building. - Most are found on oceanic plates, but the most famous are continental, e.g. San Andreas Fault. - Subduction causes oceanic trenches, such as the Mariana trench, where one plate begins its descent beneath another. - Without subduction, plate tectonics could not exist. Earth's crust would not have split into continents. Oceans and all of the solid Earth would lie beneath a global ocean. ## Transform Plate Boundaries - Also known as fault/ strike-slip/sliding/ conservative plate boundary. - The plates move away from each other. - Most exist between oceanic plates, causing oceanic rifts. - During collisions between two continental plates, large mountain ranges, such as the Himalayas are formed.