Plate Tectonics

Earth’s Layers The Earth's rocky outer crust solidified billions of years ago, soon after the Earth formed. This crust is not a solid shell; it is broken up into huge, thick plates that drift atop the soft, underlying mantle.

The Crust Outermost layer 5 – 100 km thick Made of Oxygen, Silicon, Aluminum

The Mantle Layer of Earth between the crust and the core Contains most of the Earth’s mass Has more magnesium and less aluminum and silicon than the crust Is denser than the crust

The Core Below the mantle and to the center of the Earth Believed to be mostly Iron, smaller amounts of Nickel, almost no Oxygen, Silicon, Aluminum, or Magnesium

Tectonic Plates

Plate Tectonics Greek – “tektonikos” of a builder Pieces of the lithosphere that move around Each plate has a name Fit together like jigsaw puzzles Float on top of mantle similar to ice cubes in a bowl of water

The Keys Features of Plate Tectonics (1) The Earth’s crust is constantly being created and destroyed (recycled). (2) Ocean crust, formed at divergent margins, is mafic and dense. (3) As ocean crust ages and cools, its great density relative to the continents results in subduction as plates converge. [As a result, old ocean crust cannot persist, whereas old parts of the buoyant continents can survive for eons.] (4) The other kind of plate margins, transforms, are parallel to the current motion of the plates.

How Plates Move

Mechanisms of Plate Tectonics: Ridge- Push Mantle drag convective flow of mantle 2 1 3

Mechanisms of Plate Tectonics: Plume- Driven 4

A Divergent B Convergent C Transform plates are moving apart new crust is created Magma is coming to the surface plates are coming together crust is returning to the mantle plates are slipping past each other crust is not created or destroyed

A Divergent B Convergent C Transform Continental crust  rift valley Oceanic crust  mid- ocean ridge 2 continental plates  mountain range Plates move against each other Stress builds up Stress is released  earthquake 2 oceanic plates or oceanic + continental  subduction

Different Types of Boundaries

Divergent Boundary – Arabian and African Plates

Divergent Boundary – Iceland

Divergent Boundary - Oceanic

Divergent Boundary - Continental

Convergent Boundary – Indian and Eurasian Plates

Convergent Boundary – Oceanic & Continental &

Convergent Boundary – Oceanic & Oceanic &

Convergent Boundaries - Continental &

Transform Boundary – San Andreas Fault

Scripps Classroom Connection Ridge Segment Divergent and transform boundaries can occur together at mid-ocean ridges