4+Plate+tectonics

Plate Tectonics

Theodore Co Kevin Uykingtian Peter Onglao

I. Plate Tectonics Theory

A. Plate Tectonics Theory 1. This theory explains the movement of the Earth's plates, and also the causes of earthquakes, volcanoes, oceanic trenches, mountain range formation, and many other geologic phenomenon. It also explains the Continental Drift Theory. 2. This is how it works. The plates are all moving in different directions and at different speed, and they sometimes crash together, pull apart, or sideswipe each other. The place where two plates meet is called a plate boundary.

B. Plates 1. The Earth's outermost layer, the lithosphere, is broken into 7 large, rigid pieces called plates, which are all constantly moving at different speeds. a. The 7 major plates are: African, North American, South American, Eurasian, Australian, Antarctic, and Pacific plates C. 3 Types of Plate Movement 1. Convergent plate movement a. This movement happens when two plates move towards each other. b. When an oceanic plate and a continental plate collide, part of the oceanic plate will turn into magma, and will slowly rise up. The movement of an oceanic plate going under another plate is called subduction.This can result in a volcano. The Washington-Oregon coastline of the United States is an example of this type of movement. c. When two oceanic plates meat, one subducts the other. The subducted one will become magma, and will slowly rise up, forming islands/volcanoes. Japan is an example of this movement. d. When two continental plates collide, and since continental plates are less dense than the mantle, the plates do not subduct and forms excessive folding and faulting within the two plates. The Himalaya Mountain Range is an example of this movement. 2. Divergent plate movement a. It is powered by convectional currents from the Earth's mantle. b. Rising convectional currents push on continental plates, and thus, the plates begin to move away from each other. i. Because continental plates are thicker than oceanic plates, the continental plate does not seperate as easily, and becomes a rift-shaped structure.Water flows into the rift, and as the rift becomes bigger, the water increases. The Red Sea is an example of this movement. c. Divergent plate movement can also happen on oceanic plates. i. Magma will rise up, and will form new oceanic crust, and may even form ridges. ii. When plates diverge, it also causes another part of the plate to converge. This makes the amount of crust on the Earth relatively constant. 3. Lateral Slipping plate movement a. 2 plates slide past each other. b. Pressure builds up, and earthquakes happen.

D. Plate Tectonics Formulation 1. Formulated in the 1960s and 1970s as new information was obtained about: a. The nature of the ocean floor b. The Earth's ancient magnetism c. The distribution of volcanoes and earthquakes d. The flow of heat from Earth's interior e. The Worldwide distribution of plant and animal fossils.

E. Effects of Plate Tectonis 1. Formation of fault lines, which can result in earthquakes. a. When plates move past each other or slide over each other, pressure builds up in the boundary between those 2 faults, and sometimes, the pressure is so great that earthquakes form beginning in the boundary of the 2 plates that slid past one another. 2. Volcanoes. a. In convergence, when the leading edge of a plate meets another plate, one of them turns downward. That downward motion is called subduction. Subducted plates move down into and through the asthenosphere and gradually melt, thus this magma moves up while making cracks in the crust, and forms a volcano at the top. 3. New Crust a. Plates diverge at volcanic zones in the ocean basins, the mid-ocean ridges. These are long, huge cracks, and lava rises from below. The lava rises, and freezes into new lithosphere. The two sides of the crack continually move apart, and thus the plates gain new material. 4. Mountains/Mountain Ranges a. In convergence, when two continental plates collide, the massive force creates folding in the middle, and thus mountains. 5. Rifts b. In divergence, when a continental plate is affected, it does not wholly split. This causes a "hole" that increases in size, where water can go into.

F. Evidences 1. One can observe that the 7 major continents seem to fit in like a puzzle. 2. A German scientest, Alfred Wegner got the idea that the continents drifted from to their current positions by studying the chain of mountains and that lie on the ocean floor. He observed that the mountains encircle the world. These were side-effects of the movement of the continents through convergent movement. These were only discovered during the 1950-1960s.

G. Issue related to Plate Tectonics 1. Plate tectonics contribute to the amount of heat energy in the earth's atmosphere with the release of physical heat of volcanoes and terrestrial and submarine lavas, as well as so-called greenhouse gases such as CO2 released from volcanoes (since it is the plate tectonics theory that caused the formation of volcanoes in the first place). 2. There is also the dissipation of heat from friction in compressional and transcurrent plate margins. All of this heat is the indirect result of the heat deep within the earth that drives plate tectonics in the first place.

II. Check-Up Quiz (5 points) Directions: Encircle the term that best fits in the sentence.

1. Plates are moving towards / away from each other. The place where 2 plates meet is called a (volcano, boundary, fault) 2. When plates slide over one another, it's movement is called (Lateral Slipping plate movement, Convergent plate movement, Divergent plate movement) 3. In divergent, one of the plates will turn downward in a movement called (sinking, formation, subduction) 4. One of the contributing forces of global warming is the release of CO2 from (volcanoes, faults, earthquakes). 5. (True, False) Plates move in different directions and at different speeds.

Sources: http://geology.com/nsta/convergent-plate-boundaries.shtml http://geology.com/nsta/divergent-plate-boundaries.shtml http://www.enchantedlearning.com/subjects/astronomy/planets/earth/Continents.shtml http://www.moorlandschool.co.uk/earth/tectonic.htm http://www.seismo.unr.edu/ftp/pub/louie/class/100/plate-tectonics.html http://answers.yahoo.com/question/index?qid=20080408103417AATPqYk http://www.cotf.edu/ete/modules/msese/earthsysflr/plates1.html