Plate Tectonics Theory PDF

Plate Tectoni cs. Take a look at the map below  Earth is like a big jigsaw puzzle, some continents are like puzzle pieces snapped together. Earth began as a single landmass or supercontinent called “Pangaea”. The term Pangaea comes from the Greek words “pan” means “All” a...

Plate Tectoni cs. Take a look at the map below  Earth is like a big jigsaw puzzle, some continents are like puzzle pieces snapped together. Earth began as a single landmass or supercontinent called “Pangaea”. The term Pangaea comes from the Greek words “pan” means “All” and “Gaea” means “Earth”. Pangaea means “All of Earth”. It is surrounded by a vast sea or superocean called Panthalassa.  It has been proposed that today’s continents were once joined together and gradually drifted apart as a result of tectonic forces. The continents cradle by continental tectonic plates found on the lithosphere. Layers of the Earth (Chemical Composition)  What is the Lithosphere? The crust and part of the upper mantle = lithosphere –100 km thick –Less dense than the material below it so it “floats”.  What is the Asthenosphere? The plastic layer below the lithosphere =asthenosphere The plates of the lithosphere float on the asthenosphere  Drift Theor y  Continental Drift Theory- is a theory that explained how continents shift position on Earth's surface. It is proposed by Alfred Wegener.  His theory was based upon his observations which included the following: 1. The apparent fit of the eastern coastline of South America and western coastline of Africa. 2. Similarities of plant and animal fossils in South America and some parts of African continent, which were separated by a vast ocean.  3. Similarities in the sequences of rock layers of opposite sides of the Atlantic Ocean.  Pangaea would later break into two smaller continents: 1. Gondwana- is composed of Africa, Antartica, South America, Australia and the subcontinent of India. 2. Laurasia- is composed of Asia, North America and Europe. Sprea ding Theor y In 1960, an American geologist named Harry Hess, proposed the seafloor spreading theory. “The seafloors or ocean floor are moving -not the continents- move and carry the continents along.  Plate Tectoni c Theory  Earth’s lithosphere is composed of many independent massive slabs of rocks called plates which floats on an inner pliable manner. This movement is due to the convection currents  7 Primary Plates: Eurasian Plate Australian Plate Pacific Plate- “largest primary plate” North American Plate South American Plate African Plate Antartic Plate  8 Secondary Plates: Juan de Fuca- “smallest plate” Nazca Plate Cocos Plate Carribean Plate Philippine Plate Arabian Plate Indian Plate Scotia Plate