Transcript The Mantle
The Layers of the Earth Earth Layers • The Earth is divided into 4 main layers. Inner Core Outer Core Mantle Crust The Crust Outermost layer of the Earth The Earth’s crust is like the skin of an apple. It is very thin compared to the other three layers. The crust makes up 1% of the Earth and is called the “rock and mineral” layer. The crust of the Earth is broken into many pieces called plates. At the junction of these plates some interesting things occur! Plate Tectonics Volcanoes Earthquakes Sea-Floor Spreading And what type of crust would you like with your Earth? • There are two types of crust. – Continental crust – Oceanic crust Continental Crust • Makes up the continents • Contains light colored rocks such as granite. • Floats high on the mantle Oceanic Crust • Makes up the ocean floor • Contains the dense rocks such as basalt • Thinner than the continental crust The Mantle The mantle is the layer between the crust and the outer core. The mantle is the largest layer of the Earth. The mantle is made up of MAGMA (hot molten rock). Because of the heating and cooling of liquid rock, convection currents occur. These currents force the plates of the crust to move. Mantle Zones: Lithosphere • Thin, uppermost part of the mantle and crust; rigid, brittle rock • Floats on the athenosphere, and slides around very slowly. • The upper part of the lithosphere melts rocks, forming a substance called magma. Magma • Magma (melted rock) moves like hot oatmeal. • Uneven heating causes material in the mantle to constantly and slowly rise & fall in convection currents. • Convection Currents: process by which hot fluid rises to the surface, and then sinks again, like soup being heated in a saucepan CONVECTION IN THE MANTLE CRUST MANTLE COOL LIQUID SINKS HOT LIQUID RISES OUTER CORE Mantle Zones: Asthenosphere • Hot, weak zone directly under the lithosphere • Flows at a very slow rate like hot asphalt under a heavy weight • The movement (convection currents) of the asthenosphere is the reason that the crustal plates of the Earth move Core • Deep within the Earth is the core • The core is made mostly of nickel & iron • Twice as dense as the mantle. • Main source of heat that triggers the convection currents • The core is made of two layers Outer Core The outer core of the Earth is a ball of very hot liquid metal. The outer core is made up of mostly iron and is very dense. Because this liquid metal is moving, positive and negative particles are created and released that create the Earth’s MAGNETIC FIELD. Magnetic Field Inner Core The inner core of the Earth has temperatures and pressures so great that the metals are squeezed together and are not able to move. Therefore; the inner core is a solid. The temperature in the core is nearly as hot as the surface of the SUN! Plate Tectonics • Pieces of the lithosphere that move around • Each plate has a name • Fit together like jigsaw puzzles • Float on top of mantle similar to ice cubes in a bowl of water Continental Drift Alfred Wegener 1900’s Continents were once a single land mass that drifted apart. Fossils of the same plants and animals are found on different continents Called this supercontinent Pangea, Greek for “all Earth” 245 Million years ago Split again – Laurasia & Gondwana 180 million years ago http://members.enchantedlearning.com/subjects/astronomy/planets/earth/Continents.shtml Evidence of Pangea Sea Floor Spreading Sea Floor Spreading • Mid Ocean Ridges – underwater mountain chains that run through the Earth’s Basins • Magma rises to the surface and solidifies and new crust forms • Older Crust is pushed farther away from the ridge How Plates Move http://pubs.usgs.gov/gip/dynamic/unanswered.html Different Types of Boundaries http://pubs.usgs.gov/gip/dynamic/understanding.html Divergent Boundary – Arabian and African Plates Divergent Boundary – Iceland http://pubs.usgs.gov/gip/dynamic/understanding.html Divergent Boundary Oceanic http://www.geology.com Divergent Boundary Continental http://www.geology.com Convergent Boundary – Indian and Eurasian Plates Convergent Boundary – Oceanic & Continental http://pubs.usgs.gov/gip/dynamic/understanding.html & http://www.geology.com Convergent Boundary – Oceanic & Oceanic http://pubs.usgs.gov/gip/dynamic/understanding.html & http://www.geology.com Convergent Boundaries Continental http://pubs.usgs.gov/gip/dynamic/understanding.html & http://www.geology.com Transform Boundary – San Andreas Fault www.geology.com