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1 - Earth’s Layers The Earth's rocky outer crust solidified billions of years ago, soon after the Earth formed. This crust is not a solid shell; it is broken up into huge, thick pieces (Plates) that drift on top of the soft, underlying mantle. 2 - The Crust • Outermost layer • 5 – 100 km thick • Made of Oxygen, Silicon, Aluminum 3 - The Mantle • Layer of Earth between the crust and the core • Contains most of the Earth’s mass • Has more magnesium and less aluminum and silicon than the crust • Is denser than the crust 4 - The Core • Below the mantle and to the center of the Earth • Believed to be mostly Iron, smaller amounts of Nickel, almost no Oxygen, Silicon, Aluminum, or Magnesium 5 - Plate Tectonics The Earth’s crust is broken into pieces also called Plates. The plates (pieces) are moving. The plates’ movement is driven by cooling of Earth (convection). ? ? ? Modified from USGS Graphics Convection is like a boiling pot. Heated soup rises to the surface, spreads and begins to cool, and then sinks back to the bottom of the pot where it is reheated and rises again. 6 - Plate Tectonics • Greek – “tektonikos” of a builder • 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 7 - What are the two types of tectonic plates? 1)Lithosphere 2) Asthenosphere 8 - What is the Lithosphere? Lithospheric plate • The 100-km-thick surface of the Earth; • Contains crust and part of the upper mantle; • It is rigid and brittle; • Fractures to produce earthquakes. USGS Graphics 9 - What is the asthenosphere? Asthenosphere: • Is the hotter upper mantle below the lithospheric plate; • Can flow like silly putty; and • It is an elastic solid, NOT liquid!! 10 - Different Types of Boundaries 1) Transform (2) Divergent (3) Convergent 11 - Three Basic Types of Plate Boundaries Divergent Using hands to show relative motion Transform Convergent USGS Graphics 12 - Three Basic Types of Plate Boundaries Divergent Transform Convergent USGS Graphics 13 - Divergent Boundary – Arabian and African Plates 14 Divergent Boundary – Iceland 15 -Convergent Boundary – Indian and Eurasian Plates 16 - Transform Boundary – San Andreas Fault 17 - Tectonic Plates There are a dozen large lithospheric plates (smaller plates not shown). Some plates have continents; some don’t. All are in motion. 18 - Earthquakes There are thousands of small earthquakes every day. “Strong” earthquakes ( about magnitude of 7) occur once a month. Magnitude of over 8 occur about once/year. 19 - Earthquakes & Plate Boundaries Notice that the earthquakes coincide with plate boundaries, and the deepest quakes (blue) are in subduction zones. Modified from USGS Graphics 20 - Volcanoes & Plate Boundaries Volcanoes also tend to occur along the plate boundaries. Modified from USGS Graphics 21 - How fast are the plates moving? Plates move 1-10 centimeters per year (about the rate of fingernail growth). Review • Name the 3 main layers of the Earth • What is a tectonic plate? • Name the three different types of plate boundaries and one location on Earth for each one Review • Name the 3 main layers of the Earth – Crust, mantle, core • What is a tectonic plate? – Pieces of the lithosphere that move around • Name the three different types of plate boundaries and one location on Earth for each one – Divergent, Convergent & transform What type of boundary is this? What type of boundary is this? What type of plate boundary is this?