2. Longest mountain system Encircles the Earth Peaks up to 12,000 feet high New oceanic crust is made here by magma erupting from the mantle

3. Steep sided valley splits the top of the mid-ocean ridge...called a rift valley Bill Nye_Seafloor Spreading Video Clip  Rift valley is 15–30 miles wide  This is where tectonic plates are moving apart and where magma erupts to form new oceanic crust

4. The Mid-Atlantic Ridge is splitting Iceland. The East African Rift Zone may be the next major ocean.

5.  Tectonic plates here are moving apart and new oceanic crust is created by magma erupting from the mantle ...like two giant conveyor belts slowly moving in opposite directions and transporting newly formed oceanic crust away from the rift valley seafloor spreading animation

6.  strange rocks shaped like tooth paste squeezed from a tube  form only when magma erupts underwater and quickly hardens  Magma = molten rock, minerals, gases  http://www.pmel.noaa.gov/vents/nemo/explor er/concepts/pillow_lava.html http://www.pmel.noaa.gov/vents/nemo/explor er/concepts/pillow_lava.html

7.  Basalt is volcanic rock  Rich in iron and magnetite  Grains of magnetite behave like little magnets, aligning with Earth’s magnetic field  Magma cools and “locks in” magnetite

8.  Earth’s magnetic poles have reversed themselves many times.  Stripes of rock parallel to mid-ocean ridge alternate in magnetic polarity.  The stripes match perfectly on both sides of the ridge. Khan Academy_Magnetic Reversals animation with magnetic reversals

9.  Rock samples further away from the mid ocean ridge are older than rocks closer to the mid ocean ridge.  Newly formed oceanic crust pushes older crust outward and away from the rift

10.  Oceanic crust created along the mid-ocean ridge is destroyed and recycled at a deep ocean trench  This is where tectonic plates are colliding.  The plate carrying denser oceanic crust is forced under the other plate and back into the mantle  Seafloor spreading and subduction recycle ocean floor about every 200 million years and move continents around

14.  Khan Academy." Khan Academy. N.p., n.d. Web. 24 Mar. 2012..  Kious, W. Jacquelyne, and Robert I. Tilling. "USGS Developing the Theory." This Dynamic Earth: The Story of Plate Tectonics. USGS Publications Warehouse, n.d. Web. 23 Mar. 2012. http://pubs.usgs.gov/gip/dynamic/dynamic  Thinkfilm Inc. (Producer). (2005). Greatest Discoveries with Bill Nye: Earth Science. [Full Video]. Available from http://www.discoveryeducation.com/