Changes Within the Earth Geography

The Earth’s Layers Core – center of the earth, consists of very hot metal Mantle – a thick layer of rock around the core, mobile Crust – rocky surface layer of the earth, thin like frosting on a cake

The Earth’s Layers

Plate Techtonics Lithosphere – the surface features of the earth, including soil, rocks, and landforms The lithosphere is broken into a number of moving plates Plates vary in size and thickness They slide over a hot and flexible layer of mantle The earth’s oceans and continents ride atop the plates as they move

Plate Tectonics Most earthquakes, volcanoes, and other geologic events occur along plate boundaries

Subduction and Convergence Convergence – a collision of plates Subduction – when one plate meets another and the lighter plate slides below the denser (more solid) plate Oceanic plates are more dense than continental plates

Convergent Boundary – Oceanic/Continental As the oceanic plate sinks the rock it is made of melts. Some of this will cool. Effects: Volcanoes made from eruptions of the melted plate that did not cool http://geology.com/nsta/convergent-boundary-oceanic-continental.gif

Cascade Mountains

Convergent Boundary – Oceanic/oceanic The denser plate slides beneath the other Effect: an arc of volcanic islands may form around the plate boundary http://geology.com/nsta/convergent-boundary-oceanic-oceanic.gif

Japan

Convergent Boundary – Continent/continent When two continental plates collide neither will sink Convergence is slow and violent Effect: Spectacular mountain ranges http://geology.com/nsta/convergent-boundary.gif

The Himalayas Still colliding at a rate of about 2 inches per year