What Are Earth’s Layers Unit D, Chapter 1, Lesson 1, pD6-11

Earth’s Layers Where does information about Earth’s structure come from? Drills Samples taken from first 10-12 km Hypothesis Patterns of earthquake waves traveling through Earth Materials that come out of active volcanoes

Seismic Waves Pattern in Earth with no layers

Pattern of Seismic Waves in Earth with layers

Earth’s Layers Crust: Earth’s outermost layer Continental crust made of granite Less dense Oceanic crust made of basalt More dense Mantle: layer directly below the crust 1600°C at the top and 4000°C at the bottom Hot enough to melt rock Solid rock Intense pressure pushes rock into a solid Only upper mantle is partly melted

Earth’s Layers Core: innermost layer Outer core Inner core Hot, liquid iron and nickel Inner core Hotter than 5500°C Hot enough to melt metal Solid iron Intense pressure pushes metal into a solid

Earth’s Layers Zones Lithosphere Asthenosphere Includes all crust and part of upper mantle Cool, solid part of Earth Lithos- Greek for “stone” Asthenosphere Part of the upper mantle Partly melted rock in upper mantle Asthenes- Greek for “weak”

Earth’s Plates 7 major lithospheric plates Float on asthenosphere – partly melted rock Plasticity: it can flow (like silly putty) Convection currents in asthenosphere caused by heat from Earth’s center Hot mantle Less dense hot mantle pushed up by more dense cooler rock Hot rock spreads out & cools Cooler, more dense rock sinks Lithospheric plates move asthenosphere flows Plates constantly move A few centimeters each year Lithospheric plates constantly change in shape and size Plates slit across new lines Combine with other plates Slide under another plate to become mantle rock again Earthquakes and volcanoes usually found at plate boundaries

Earth’s Plates African Plate: Major plates names after continents or oceans they carry North American Plate: North America & Atlantic Ocean South American Plate: South America & Atlantic Ocean Australian-Indian Plate: Australia, India, & Indian Ocean Antarctic Plate: Antarctica & Pacific, Atlantic, & Indian Oceans Pacific Plate: Pacific Ocean African Plate: Africa & Atlantic & Indian Oceans Eurasian Plate: Europe & Asia & Atlantic Ocean

Earth’s Plates Plate tectonics: theory scientists use to explain plate movements Tectonics Greek word meaning “builder” Plate movements build Earth’s largest landforms Plates move, break apart, collide

Earth’s Plates Most plates contain both oceanic and continental crust Oceanic crust Newer, thinner, under oceans Continental crust Older, thicker, land

Changes to Earth’s Surface Earth’s surface is constantly being changed Movement of plates Move continents around the globe Form mountains Causing earthquakes & volcanic eruptions Erosion and deposition Water and wind erosion carve out valleys, cliffs, and caves Rivers deposit sand and rock on its banks & at mouth Wind picks up sand and deposits it on dunes

Changes to Earth’s Surface Earth’s surface is constantly being changed Glaciers Erodes land and deposits rock, sand, and mud Rocks & pebbles pulled by glacier act like sandpaper Gravity pulls glacier downhill Glaciers melt and deposit material Form ridges, hills, gravel-covered plains Objects from space Meteoroids – chunks of rock moving through solar system Enter Earth’s atmosphere Friction causes it to heat-up & burn Meteor = streak of light, “shooting star” Meteorite = meteoroid that hits the ground Most too small to notice Comets & asteroids

Summary Earth is composed of inner core, outer core, mantle, & crust Lithosphere = crust + part of upper mantle Theory of plate tectonics explains how lithospheric plates move causing changes to Earth’s surface Other changes to Earth’s surface caused by: Wind & water Glaciers Space objects that hit Earth

Homework Read Unit D, Chapter 1, Lesson 1, pD6-11 Answer ?s on Google form