Download
1 / 14
140 likes | 150 Views
Explore the fascinating world of plate tectonics and its impact on the Pacific Northwest. Learn about the Earth's layers, how plates move, and the different types of plate boundaries. Discover the processes behind divergent, convergent, and transform-fault boundaries, and their effects on the region's geography. Delve into the unique geological features and formations created by plate tectonics in the Pacific Northwest.
E N D
Plate Tectonics Pacific Northwest Mr. Rice February 14, 2011
In the beginning… • Scientific evidence shows that out of a cloud and fire storm from the sun, four billion six hundred million years ago, earth was created… • The sun burns the barren earth where there are no seas and poisonous gases gasp the inhospitable world… • For thousands of years the earth is covered by molten lava and is racked by volcanoes and asteroids.
Eventually… layers form! • Slowly, the earth cools and separates into multiple different layers. • Heavy metals, mostly iron, settles to the inner core at the center of the earth. • The inner core is slowly concealed in a nickel and iron outer core that is less dense. • Surrounding the inner and outer core is the mantle, that is itself split in to many layers. • Over the mantle is the Earth’s crust, a thin veneer of rocky material that covers the planet like the cracked, twisted, lumpy crust of an apple pie.
Plate Tectonics • Once thought to be one solid piece of rock, the earths crust is theorized to be made up of many jostling plates. • The plates are between 4-40 miles thick. • These enormous blocks of Earth’s crust vary in size and shape, and have definite borders that cut through continents and oceans alike. • There are nine major plates and many other smaller plates.
How do Plates Move? • Because the inner core is hot, because of radioactive activity and the immense pressure, rock melts as it dives downward. • Then because of hot things rise and cold things sink the liquid hot magma rises and hard rock sinks, creating circulation. • This circulation is called convection currents • Convection currents are the reason that the light plates move over the mantle.
Types of Plate Boundaries • Divergent Boundaries – Where earth is created as two or more plates pull apart from each other. • Convergent Boundaries – Crust is destroyed and recycled back into the interior of the Earth as one plate dives under another. • Oceanic-Continental Convergent • Continental-Continental Convergent • Transform-Fault Boundaries – Where two plates are sliding horizontally past each other.
Oceanic-Continental Convergence • When an oceanic plate pushes into and subducts under a continental plate, the overriding continental plate is lifted up and a mountain range is created. Even though the oceanic plate as a whole sinks smoothly and continuously into the subduction trench, the deepest part of the subducting plate breaks into smaller pieces.
Continental-Continental Convergence • When two continents meet head-on, neither is subducted because the continental rocks are relatively light and, like two colliding icebergs, resist downward motion. Instead, the crust tends to buckle and be pushed upward or sideways. The collision of India into Asia 50 million years ago caused the Eurasian Plate to crumple up and override the Indian Plate. After the collision, the slow continuous convergence of the two plates over millions of years pushed up the Himalayas and the Tibetan Plateau to their present heights. Most of this growth occurred during the past 10 million years.
