Earth Science – Chap. 2 – Sect.1

1. Earth Science – Chap. 2 – Sect.1 Objectives 1. List the characteristics of earth’s three compositional zones and 5 structural zones 2. Explain how studies of seismic waves have provided information about earth’s interior 3. Define magnetosphere and identify the possible source of earth’s magnetism 4. Summarize Newton’s law of gravitation

2. STATE SCIENCE STANDARDS • Recognize that the force of gravity keeps planets in orbit around the sun and influences objects on Earth and other planets (i.e., tides, ability of humans to move and function). Differentiate between an object’s mass and weight. • Investigate how thermal convection relates to movement of materials. Apply this knowledge in explaining the cause of movement of the Earth’s plates. • Describe energy sources, processes, and transformations of Earth materials as they progress through the rock cycle to form new sedimentary, metamorphic, and igneous rocks. Discuss how the cycling of rock is continuous.

3. Earth Stats • Earth is not a perfect sphere • Earth is an oblate spheroid • Circumference around poles = 40,007 km • Circumference around the equator = 40,074 km • The spinning of the earth causes centrifugal force, causing the poles to flatten and the equator to bulge • Distance between highest mountain and lowest part of ocean = ~ 20 km. • Average diameter of earth = 12,735 km.

4. OBLATE SPHEROID

5. Hydrosphere • Earth cover by 71% water • 97% of that water is salt water • 3 % fresh water is in lakes, river, streams, groundwater and frozen in glaciers and icecaps. • 1% available for use by living organisms • All of earth’s water is know as the hydrosphere

6. HYROSPHERE

7. Atmosphere • The gases in the earth’s atmosphere supply oxygen to living organisms and shield the earth from harmful solar radiation • 78% - nitrogen • 21% - oxygen • Last 1% includes: CO2 , argon and helium

8. CARBON DIOXIDE IN THE ATMOSPHERE • What does 400 ppm mean? • .04% of atmosphere • 400 parts of Carbon Dioxide per 1 Million parts of atmosphere • Why is carbon dioxide so important in today’s society?

9. LIVING ORGANISMS AND NITROGEN • Nitrogen is an essential component for life on Earth and makes up 78% of the atmosphere. • If humans need nitrogen to survive do we get t from the atmosphere like we get Oxygen? • If not, where do we get it?

10. NITROGERN-FIXING BACTERIA

11. PLANTS WITH NITROGEN_FIXING BACTERIA

12. LET’S EXPLORE NITROGEN_FIXING BACTERIA • With your partner gather some samples of clover from the A.I. Nature Area • Be careful to gently pull the plant from the ground preserving the root system • Locate the nitrogen-fixing bacteria nodules attached to the roots • Carefully place them onto a slide and observe them under a microscope • Make some observations in your notebooks!

13. Earth’s Interior • Scientists use seismic waves to speculate on the composition of earth’s interior • Seismic waves are vibrations that travel through the earth • Seismic wave studies have helped scientist determine that the earth is made up of three (3) major zones – compositional • (5) structural zones

14. EARTH’S LAYERS

15. Compositional Zones of the Earth • Crust: thin, outermost zone of earth • Makes up 1% of earth’s mass • Oceanic crust found beneath oceans • Between 5 and 10 km. Thick • Dense • Composed of mostly iron and magnesium • Continental crust makes up continents • Between 15 and 80 km. Thick (thickest beneath mountain ranges) • Less dense • Composed mostly of silicon and oxygen

16. Compositional Zones Continued • Mantle: zone below crust • Nearly 2,900 km thick (1,798 miles) • Makes up almost 2/3’s of earth’s mass • Core: below mantle and forms center of earth, made mostly of iron, makes up approx. 1/3 of earth’s mass

17. 5 - STRUCTURAL ZONES Lithosphere: the uppermost part of mantle and the crust. A rigid layer 15 – 300 km. Thick Asthenosphere: just below the lithosphere, approx. 200 km. Thick, plastic like (solid rock with ability to flow due to enormous temp. and pressure) Mesosphere: Below the Asthenosphere – solid rock- Approx. 2900 km • Outer core: dense, liquid layer about 2,250 km. Thick (1395 miles) • Inner core: dense, solid sphere with a radius of 1,228 km. (761 miles)

18. Seismic Waves • Primary waves (p-waves): travel through solids, liquids and gases. Travel faster than s-waves • Secondary waves (s-waves): only travel through solids, slower than p-waves • Speed and direction of p and s waves affected by composition of material they travel through • Both waves travel faster through more rigid materials

19. The Moho • In 1909 AndrijaMohorovicic, a Croatian scientist, discovered that the speed of seismic waves increases abruptly 32 to 70 km below earth’s surface. This change in speed marks the boundary between the crust and the mantle and is known as The Mohorovicic Discontinuity or simply The Moho. • The increase in speed indicates that the mantle must be denser than the crust.

20. AndrijaMohorovicic- -THE MAN!

21. Other Changes in Wave Velocity • Approx. 100 km below the Moho the waves decrease in velocity at the boundary between the lithosphere and the less dense asthenosphere • Seismic waves increase in speed after this boundary until approx. 2,900 km. • At 2,900 km, p-waves slow down and s-waves disappear entirely. This marks the boundary between the mantle and the outer core (liquid) • At a depth of approx. 5,150 km (3,193 miles) the p-waves speed up again marking the boundary between the outer core and the inner core (dense solid)

22. Shadow Zones • Locations on earth’s surface where neither s-waves nor p-waves are detected (or where only p-waves are detected) • Caused by earth’s non-uniform composition of materials which causes the waves to bend and change direction due to speed differences of the waves • S-waves cannot travel through the liquid outer core and p-waves bend with different density materials forming shadow zones

23. SHADOW ZONE

24. Earth as a Magnet • Earth has two magnetic poles: • The Northern Geomagnetic Pole and the Southern Geomagnetic Pole with lines of force between the two • Magnetosphere: the area of space that extends beyond the atmosphere that is affected by the magnetic field • Magnetic field thought to be generated by the flow of liquid iron in the outer core due to the conductivity of the iron producing electrical currents • Problem: the moon and sun both have a magnetic field but the sun has very little iron and the moon has no liquid core. This indicated that there may be some other force producing the magnetic fields.

25. Earth’s Gravity • Gravity: the force of attraction that exists between all matter in the universe, discovered by Sir Isaac Newton and described in his law of gravitation • Law of Gravitation: states that the force of two objects depends on their masses and the distance between them. The larger the masses of the two objects and the closer together they are, the greater will be the force between them.

26. Earth’s Gravity • The mass of the earth exerts a force of gravity that pulls objects toward the center of the earth. • Weight: the measure of the strength of the pull of gravity on an object. (measured in Newtons- on earth’s surface 1 kilogram of mass weighs about 10 N) • How much would a mass of 2-kg weigh? • How much would a mass of 10-kg weigh?

27. Weight and Mass • Mass: the amount of matter in an object • Weight: the force of gravity on an object • Mass of an object does not change with location, weight does • The weight of an object depends on its mass and the distance from the earth’s center • An object would weigh approx. 0.3 % less at the equator than at the North Pole due to the difference in distance from the center of the earth.

28. QUIZ – CHApter 2, sect 1 • QUIZ

29. HOMEWORK • Read Chapter 2, sections 2 & 3 • Do section reviews 2.2 & 2.3- • 1 – 12, 1 - 10

30. EXIT TICKET • Would a person weigh more at the North Pole or the Equator? Why? • What is meant by 400 ppm? Why is it significant in today’s society? • Describe the Moho. • Describe the difference between a “P” wave and an “S” wave.