1. Planet Earth The Composition and Layers of the Physical Earth. Earth Science Review Book - Chapter 1 Earth Science Review Book - Chapter 1 Holt Text – Chapter 2 Holt Text – Chapter 2 Earth as a System Topic1A

2. 2 Chapter Objectives: The Earth as a system. How large is the Earth? What is the Earth’s shape? Evidences… The spheres of the Earth and their compositions. AtmosphereHydrosphereGeosphere

3. 3 Earth as a System Earth is a dynamic body with many separate but highly interacting parts or spheres Earth as a system Consists of a nearly endless array of subsystems (e.g. hydrologic cycle, carbon cycle) Sources of energy Sun - drives external processesSun - drives external processes –Weather and climate, Ocean circulation & Erosional processes Earth's interior – nuclear, chemical & thermal energy drives internal processesEarth's interior – nuclear, chemical & thermal energy drives internal processes –Volcanoes, Earthquakes & Mountain building Humans are part of the Earth system

4. 4 Earth’s Size Earth’s circumference - distance around the earth was first measured by Eratosthenes 2000 years ago. Measured distance between Egyptian cities of Alexandria and Syrene. Measured sun’s angle at noon at each location. Difference in angle is a fraction of a circle. Multiply distance by fraction to get circumference. Obtained 46,250 km, very close to the real 40,000 km circumference!

5. 5 Eratosthenes Method

6. 6 Earth’s Numbers Polar Equatorial Polar Equatorial Diameter 12,714 km 12,756 km Polar Equatorial Polar Equatorial Circumference 40,007 km 40,074 km

7. 7 The Earth’s Shape The shape of the Earth is usually thought of as a _______________. Sphere Oblate Spheroid Oblate Spheroid From observations & measurements by earth scientists we know that the Earth is slightly flattened at the poles and slightly bulging at the equator. Thus the shape is called a(n) _____________ _____________

8. 8 Earth’s Shape – Due to the Earth is spinning on its axis so it slightly bulges at the equator and flattens at the poles. Earth Looks Spherical from Space

9. 9 Evidence of Nearly Spherical Shape 1.As we now know that the Earth is not flat as was once believed. Columbus 2.Another evidence is Star paths through the sky. One of the best known stars is the North Star (POLARIS) We can observe many stars traveling in a circular or curved pattern over time around Polaris.

10. 10 Star Trails (Time Lapse Photography) Photograph by Josh Walawender: http://www.ifa.hawaii.edu/~joshw/Astrophotos/2006_06_30/KeckLGS_Trails.html

11. 11 Other Evidences… 3. Ship masts appear 1st on horizon. 4. The angle of the North Star changes when you move north or south. This could only happen on a spherical surface. 5. Earth’s shadow is curved when seen during a lunar eclipse. 6. Astronauts have photographed the earth from space.

12. 12 Spheres of the Earth Geosphere: Consists of all the rock and fluid inner layers of the Earth. Hydrosphere: Consists of all the water on Earth’s surface; oceans, rivers, lakes streams etc. Covers ~71% of surface. Atmosphere: Consists of the shell of gases that surrounds the Earth.

13. 13 Spheres of Earth

14. 14 Average Chemical Compositions ESRT - Front Cover

15. 15 Percent Composition of the Atmosphere Our atmosphere is mostly nitrogen (78%) followed by Oxygen (21%); CO 2 makes up less than 1%

16. 16 Atmosphere Layers

17. 17 Properties of the Atmosphere ESRT - Page 14 Troposphere Stratosphere Mesosphere Thermosphere OZONE

18. 18 OZONE DEPLETION The ozone absorbs harmful UV rays from the Sun. Depletion caused by CFC’s (ChloroFluoroCarbons) found in aerosols, Styrofoam and refrigerants. Problem from ozone depletion is increased skin cancer in humans and animals.

19. 19 Ozone Depletion

20. 20 Atmospheric Phenomena Aurora Borealis in Ionosphere over Canada Light IONS Sun Rays Ionosphere Photograph of Northern Lights from Space - NASA

21. 21 Northern Lights

22. 22 Hydrosphere All the water on the Earth = ~71% of Surface. Freshwater [2%] – Rivers, Lakes, streams, & marshland. Marine [97%] – Saltwater Oceans Ice [1%] – Continental and Mountain glaciers

23. 23 The Structure of Earth’s Geosphere Moho Page 28 in Text

24. 24 Compositional Zones Crust- The thin solid outer most zone- Continental & Oceanic crust 1% of Earth’s mass. Lower boundary is the MOHO. Mantle- Below the crust; denser than crust and 66% of Earth’s Mass. Core- Composed mainly of Iron and Nickel. Outer core is a dense liquid, Inner Core is dense solid. 33% of Mass.

25. 25 Structural Zones The three compositional zones are divided into five structural zones. Lithosphere- Crust and cool brittle upper mantle. 15-300 km thick Asthenosphere- Less rigid layer with the ability to flow due to enormous heat and pressure. (plasticity) 200-250 km thick Stiffer Mantle- Layer of solid mantle rock. Outer Core- dense liquid mostly iron Inner Core - dense solid of iron and nickel

26. 26 ESRT – Page 10 1.What happens to density from the crust towards the inner core? 2.What happens to pressure as you go towards the core? 3.What happens to temperature as you go towards the core? 4.Which layers are Liquids (Above the melting point?) 5.What is the depth of the boundary between the Mantle & Outer Core? Density Increases Pressure Increases Temperature Increases Depth

27. 27 How do We know? From Seismic Waves. Scientists studying earthquakes have found that seismic waves travel through the Earth’s interior at different speeds and directions. The differing speeds are due to different densities of the existing zones or layers. These Seismic waves are called P and S waves.

28. 28 Seismic Waves The Seismic Waves change speed and direction as they pass through layers of different densities. Notice the S-waves do not travel through the liquid outer core.