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

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

3. Seismic Waves Pattern in Earth with no layers

4. Pattern of Seismic Waves in Earth with layers

5. 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

6. 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

7. 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”

8. 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

9. 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

10. 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

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

12. 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

13. 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

14. 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

15. Homework Read Unit D, Chapter 1, Lesson 1, pD6-11
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