Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
#20 Plate Tectonics Plate Tectonics 20 Earth’s crust is broken into large pieces called _________________ . tectonic plates These plates move across the surface of the Earth because of __________________ in Earth’s convection currents ___________________ . mantle Continents have ___________ , ______________ collided broken apart and _________________________ at different times reformed in Earth’s past. Pangea _______________________________ is the super continent that formed _______________________ . About 240 million years ago Pangea "whole earth" __________________ means ____________________________ . There are three main kinds of plate boundaries: Convergent: two plates run into each other _______________________________________ Divergent: two plates move away from each other ______________________________________ Transform: two plates slide past each other ______________________________________ page 5 Plate boundaries are mapped in the ESRT on _____ 1 #20 Plate Tectonics Divergent Boundaries What happens here: • Two pieces of crust move apart. • Magma from the mantle seeps into cracks created by expansion • New crust is created Land forms associated with divergent boundaries: a. midoceanic ridges b. volcanoes Evidence supporting the existence of divergent boundaries: a. crust gets older as you move apart from ocean ridges b. alignment of magnetic field in ocean crust 2 #20 Plate Tectonics Convergent Boundaries What happens here: Two pieces of crust collide into each other Differences between oceanic and continental crust: a. Oceanic: Thinner and more dense b. Continental: Thicker and less dense Land forms associated with Convergent Plate boundaries: a. Mountain Ranges b. Island Arcs c. Ocean trenches d. Fault zones & volcanoes Original Horizontality: The idea that strata (layers of rock) were originally flat layers. As plate collisions happen, rock is bent, deformed and uplifted. Deposition: rocks formed in flat layers Deformation: rocks lifted, bent, flipped over OceanicContinental Collision • A piece of oceanic crust collides with a piece of continental crust • The oceanic crust is more dense, so it subducts. • The continental crust is less dense, so it overrides. • Intense pressure causes rock to melt into magma below the collision • Magma rises and creates a mountain range that may contain volcanoes. Rock is uplifted and deformed. Rock becomes metamorphic. 3 #20 Plate Tectonics ContinentalContinental Collision • Two pieces of continental crust collide with each other • They have similar densities, so material from both plates is uplifted • Intense pressure causes rock to melt into magma below the collision • Magma rises and creates intrusions of igneous rock OceanicOceanic Collision • Two pieces of oceanic crust collide with each other • One subducts (dives down), the other overrides (goes over top) • Intense pressure causes rock to melt into magma below the collision • Magma rises and creates a chain of volcanoes called an island arc. 4 #20 Plate Tectonics Transform Boundaries What happens here: Two plates slide past each other Things associated with transform boundaries: a. Fault zones: a line of breaks in the Earth's crust, like the San Andreas Fault. b. Earthquakes: as the plates move, they often jam against each other. Energy builds up until it is released all at once, causing an Earthquake 5