Plate Tectonics -- Exam #1

A
Plate tectonics cause seafloor spreading, mid-ocean ridges, subduction zones, earthquakes, volcanoes, and mountain ranges. Seafloor spreading occurs at divergent boundaries. Seafloor spreading is when two plates move apart and lava flows up to fill the gap. Iceland is on a divergent boundary.[1] [1]
Mid-ocean ridges, earthquakes, and volcanoes occur when two oceanic plates collide and produce mountains. The total length of the underwater mountain range is about 60,000km.[2] these mountains may form island chains. [1]
B

Rocks in Earth's core become heated by the core, and lose density. The rocks rise and cool off and fall again. This creates a circular motion in Earth's mantle, thus creating currents through the magma and pushing plates.[1]


C
Plate tectonics are believed to have caused continental drift.[3] Scientists think that the continents move about one yard per century. "These plates move relative to one another above a hotter, deeper, more mobile zone at average rates as great as a few inches per year." [3] Island chains are formed by underwater volcanoes that erupt multiple times and form islands. The debris from the volcano builds up into a large volcano that pierces the sea level. (See image titled "Oceanic-oceanic convergence") Transform boundaries create geological differences by sliding past each other(California is an example). Such boundaries form faults such as the San Andreas.
Hawii was formed by a hot spot that stayed in one stationary spot, forming volcanoes. The tectonic plate beneath Hawaii moved Northwest, resulting in many volcanoes being formed in a chain. [4] These volcanoes erupted multiple times to form the Hawaiian islands.
California might eventually break apart due to a change in tectonic plates. The plates have been moving at a rate of about 5cm per year, and scientists predict that the western side of California will separate all together. The plate boundary lies on the San Andreas fault. As I said before, this is a Transform boundary, so we don't see the 5cm difference. Eventually this boundary may become divergent, creating a much wider fault.
[1] http://www.platetectonics.com/book/page_5.asp, Plate Boundaries, November 23, 2009, Thomas, Lewis
[2] http://www.waterencyclopedia.com/Mi-Oc/Mid-Ocean-Ridges.html, Mid-Ocean Ridges, 2009, Gilman, Larry & Lerner, K.
[3] http://www.infoplease.com/ipa/A0001765.html, Continental Drift and Plate-Tectonics Theory, 2007, U.S. Dept. of the Interior, Geological Survey
[4] http://en.wikipedia.org/wiki/Hawaii#Geography_and_environment, Hawaii, 2009, Wikipedia