8 Plate Movement

8 PLATE MOVEMENT Continental Drift - a theory that explains the relative displacement of continents through geologic time Pangea - a supercontinent that broke apart during the Paleozoic Era and drifted to the positions that we observe today Plate tectonics - a theory in geology that says that the Earth's crust is composed of a mosaic of large, slowly moving plates Lithosphere - the thinnest and the most rigid of the earth that contains all the rocks beneath the oceans (oceanic crust) and on the continents (continental crust) Asthenosphere - a layer of soft, partially molten rock that lies below the rigid lithosphere (crust) Divergent Boundary - a zone in the earth's crust along which tectonic plates are separating Rift valley - in the oceans, a deep central fracture found along the crest of the mid-ocean ridge. On land it is an elongated valley that overlies a region of stretching crust Mid-Ocean Ridge - a submarine mountain chain found along divergent plate boundaries where new oceanic crust is actively forming Sea-Floor Spreading - a theory that explains how new oceanic crust is forming by the convective upwelling of magma at mid-ocean ridges and how it then moves away at rates of 1 to 10 centimeters per year Convergent Boundary - a zone in the earth's crust along which tectonic plates are colliding Subduction Zone - an elongated region where colliding plates force one crustal plate below resulting in deep ocean trenches and chains of mountains or volcanoes Transform Boundary - a zone within the Earth’s crust along which tectonic plates are sliding past each other Hot Spot - a relatively fixed but isolated region of volcanic activity that is marked by a trail of extinct volcanoes Plate Tectonics ☆ About 260 million years ago, the continents were joined together in the supercontinent Pangaea. About 225 million years ago, Pangaea began to break apart. Ever since then, the continents have moved to their now present locations. ☆ The Earth’s crust and upper mantle is broken into sections called plates which move around on top of the mantle due to Convection Currents. ☆ Heat energy from the Earth’s core spreads outwards which causes tremendous amounts of heat in the asthenosphere, resulting in Convection Currents. ☆ These currents cause hot materials to rise and expand and cool materials to sink and contract. Types of Crust: 1. Oceanic Crust - plates that float below oceans. These plates are thinner, desert, composed of basalt, and are high in iron content. 2. Continental Crust - plates that float below continents. These plates are thicker, less dense, composed of granite, and are high in silica content. Types of Plate Boundaries: 1. Divergent - plates that move away from each other. 2. Transform - plates that slide past each other. 3. Convergent - plates that move towards each other. Divergent Plates ☆ Divergent plates move away from each other to form divergent boundaries. As these plates move apart, new materials come up to fill that space. Oceanic Divergent Boundaries: ☆ This activity takes place on oceanic crusts. ☆ Formed at the Mid-sea ocean ridge. ☆ When a divergent boundary develops on land, two slabs of Earth’s crust slide apart. A deep valley called a rift valley forms along the divergent boundary. ☆ Can often cause shallow earthquakes or volcanoes. Continental Divergent Boundaries: ☆ This activity takes place on continental crusts. ☆ Forms at the rift zones, volcanic mountain ranges to split by a rift valley, or where basalt flows. ☆ Can often cause shallow earthquakes or volcanoes. ☆ Transform Plates ☆ Transform plates slide past one another to form transform boundaries. These plates can move in the same direction, but at different speeds. ☆ Features: - Possible earthquake scars. - Often no features visible. ☆ Often causes extensive earthquake activities. San Andreas Fault: Convergent Plates ☆ Convergent plates move towards each other to form convergent boundaries. ☆ Continent-Continent Collision ☆ Two continental crust come together with force and collide and material gets pushed upwards. ☆ Usually from large mountains and cause extensive earthquakes. Continent-Oceanic Collision ☆ dense plate. ☆ Results in deep earthquake activity, subduction of oceanic plates, and explosive volcanism. Oceanic-Oceanic Collision ☆ Two oceanic crusts come together with force and collide and the denser plate will sub duct under the less dense plate. ☆ Results in deep earthquake activity, subduction of oceanic plates, and explosive volcanism.