1. EARTH
OUR HOME IN SPACE

2. Standards Understand the scale and contents of the universe
Explain plate tectonics and understand the evidence that supports it

3. Earth is best studied terrestrial planet
We can draw on our knowledge of Earth to aid us in our understanding of other planets

4. Earth Data

5. Formation of Earth Earth formed out of solar nebula
Formed at same time as other planets (4.6 billion years ago)
Started out as rocky ball of uniform composition and density

6. Earth began to heat & melt
3 sources of heat:
1. gravitational collapse
2. radioactive decay
3. bombardment by meteorites

7. Differentiation occurs
Differentiation is the formation of layers.
Heavier elements sank to middle of molten Earth.
Lighter elements floated on top.

8. Layers of Earth (compositional)
Earth is composed of three main layers, defined by what they are made of:
Core
Mantle
Crust

9. Core Made of iron & nickel Inner core:
solid – hot, but too much pressure to be in liquid state.
1255 km thick.
Outer core:
liquid – rotates around inner core (rotation causes magnetic field).
2220 km thick.

10. Mantle Region surrounding core Makes up bulk of Earth 2900 km thick
Composed of peridotite (rock containing iron and magnesium)
Solid that flows (plastic)

11. Crust Thin, outer layer of Earth Solid Two types: Oceanic crust –
thinner than continental crust.
Made of basalt (volcanic rock).
7 – 10 km thick.
2. Continental crust –
made of granite.
20 – 70 km thick.

12. Other Layers (mechanical)
Defined by how they behave
Lithosphere – layer which includes crust and uppermost mantle.
Asthenosphere – part of mantle directly below lithosphere.

13. How do we know layers of Earth?
Drilling has only been done to a few km depth (still in crust)
Structure known because of seismic waves.

14. Seismic Waves Vibrations that travel through Earth.
Produced by earthquakes or explosions on surface.
Waves refract (or bend) at boundaries between layers (because layers composed of rocks of different densities).

15. 2 types of seismic waves
Surface waves – travel on surface – not good for studying interior.
Body waves – travel through Earth. 2 types:
1. primary or P waves
2. secondary or S waves

16. Primary or P Waves 1st to arrive at seismic station.
Compressional wave.
Can travel through solids & liquids.

17. Secondary or S Wave Arrive after P waves Shear wave
Can travel through solids, but not liquid.
Don’t travel through outer core  outer core is liquid

18. S Wave Shadow Zone
Zone in which no S waves are recorded by seismic stations.

19. Plate Tectonics
Lithosphere is broken up into segments (tectonic plates) that move upon the partially molten mantle – called Plate Tectonics.
Movement of plates responsible for many of Earth’s processes and features, such as mountains, volcanoes and earthquakes.
Movement recycles oceanic crust (crust is created and destroyed).

20. Tectonic Plate Map

21. Types of Plate Boundaries
Plates move relative to each other along one
of three types of boundaries
Convergent boundary
Divergent boundary
Transform boundary

22. Convergent Boundary Where two plates collide. 3 Types:
oceanic-continental
oceanic crust is more dense and sinks beneath continental crust.
Called subduction zone.
Where crust is destroyed.
Cause volcanoes and earthquakes.

23. Mt. St. Helens

24. Convergent Boundary 2. Continental-continental
both crusts of same density, so neither sinks.
Push together and cause mountain building.
Ex: Himalayan Mountains

25. Himalayas

26. Convergent Boundary 3. Oceanic – oceanic:
older oceanic crust is cooler and denser, so the older of the two crusts is subducted.
Forms island arcs, which are volcanically active.
Ex: Soufriere Hills Volcano, Montserrat (island in the West Indies)

27. Soufriere Hills, Montserrat, West Indies

28. Divergent Boundary Where two plates pull apart.
This is where new crust is made.
Associated with volcanoes and earthquakes
Exs: Mid-ocean ridges
Rio Grande Rift (formed Albuquerque Volcanoes).

29. Iceland: Mid-Atlantic Ridge at Surface and Icelandic Volcano

30. Transform Boundary Where two plates slide past each other.
Causes earthquakes
Ex: San Andreas Fault

31. San Andreas Fault
Nimitz Freeway collapse during
1989 Loma Prieta earthquake

32. What Drives Plate Motion?
Convection in Earth’s mantle – hot material rises & cool material sinks
What other body in the solar system has convection?
The sun

33. Other Parts of Earth
Hydrosphere
Atmosphere
Magnetosphere

34. Hydrosphere
Includes all the water on Earth that is contained in the oceans, glaciers, streams, lakes, soil, groundwater & air.
The oceans comprise 70% of Earth’s total surface area
Water moves between these different locations through a process called the hydrologic cycle

36. Earth’s Atmosphere Air above Earth’s surface. Breathable by humans
Mixture of gases:
78% nitrogen
21% oxygen
Trace amounts of argon, carbon dioxide & water vapor
Large amount of oxygen makes Earth’s atmosphere unique in solar system.

37. Structure of Atmosphere
Troposphere – region where convection (and weather) occurs. Up to ~12 km in altitude.
Stratosphere – contains ozone layer
Mesosphere – where meteorites burn up
Thermosphere – topmost layer, above ~80 km. Where aurorae occur.

38. Layers of Atmosphere

39. Origin of Earth’s Atmosphere
Atmosphere of early Earth made up of gases most common in solar system (hydrogen, helium, methane, ammonia & water vapor)
Escaped into space

40. Origin of Earth’s Atmosphere
Secondary atmosphere was outgassed (expelled) from planet’s interior by volcanoes
Surface temperature fell and water vapor condensed, forming oceans
Water in oceans also provided by comets impacting Earth
Life appeared in oceans and began to produce oxygen
Oxygen in present-day atmosphere is direct consequence of evolution of life on Earth.

41. The Magnetosphere
Zone of charged particles at high altitude, trapped by magnetic field.
Completely surrounds planet
Magnetic N & S poles: where magnetic field lines intersect Earth’s surface. Aligned with axis.
Protects Earth from solar particles.
Auroras occur when solar wind interacts with magnetosphere

43. Life
Earth is the only known planet to contain life, and it contains lots of it