1. Earth’s Size and Shape

2. Formation of Earth
 Most researchers conclude that Earth and the other planets formed at essentially the same time.
 Nebular Hypothesis
The solar system evolved from an enormous rotating cloud called the solar nebula.

3. Nebular Hypothesis
• The nebula was composed mostly of hydrogen and helium.
• About 5 billion years ago, the nebula began to contract.
• It assumed a flat, disk shape with the protosun (pre-Sun) at the center.
• Inner planets begin to form from metallic and rocky clumps.
• Larger outer planets began forming from fragments with a high percentage of ices.

4. The Nebular HypothesisC D E B
The nebular hypothesis is about how our solar system formed
The big bang is how the universe was formed

5. Layers Form on Earth
• As Earth formed, the decay of radioactive elements and heat from high-velocity impacts caused the temperature to increase.
• Lighter rocky components floated outward, toward the surface.
• Gaseous material escaped from Earth’s interior to produce the primitive atmosphere.

6. Earth’s Shape Kind of like an egg…
• VERY CLOSE TO BEING A PERFECT SPHERE
• actual shape: OBLATE SPHEROID
FLATTENING AT THE POLAR REGIONS
SLIGHT BULGE AT THE EQUATOR
Kind of like an egg…

7. Therefore the equatorial diameter is larger… about 43km larger then the polar diameter
Polar Diameter: 12,720 Kilometers (7,900 miles)
Equatorial diameter is 12,750 kilometers (7,922 mi) 

8. What evidence is there that we are slightly oblate?
Gravity measurements.
Gravity is the force of attraction between any 2 objects.
Increase mass of objects = increase in gravity
Decrease of distances = increase in gravity
If Earth were a perfect sphere, it would be expected to exert an equal force on objects at equal distances from the center of earth.

9. Weight!!! – measure of gravitational force
We are further from the center of the Earth at the equator – gravity is less
This means we weigh LESS!!!
We are closer at the poles…
We weigh MORE!!!!
The least amount of gravity is farther from the center of Earth
The amount is minimal but still evidence for the shape of earth

10. Why is the earth not perfectly round?
Earth’s rotation causes…
Bulging at equator
Flattening at the poles

11. Evidence for how we know the earth is round at all and not FLAT
1.) Photographs from outer space 2.) Ships appear to sink gradually below horizon 3.) Spherical shadow cast during an eclipse of the moon 4.) The angle of polaris above the horizon would not change on a flat earth

12. 2.) Ships appear to sink gradually below horizon
EVIDENCE
that Earth is round and not flat.
1.) PHOTOGRAPHS FROM OUTER SPACE
2.) Ships appear to sink gradually below horizon

13. EVIDENCE
3.) SPHERICAL SHADOW CAST DURING AN ECLIPSE OF THE MOON

14. Lunar Eclipse
Only a sphere can cast a shadow that appears round. During a lunar eclipse, the earth casts its shadow on the moon during the full moon phase.

16. EVIDENCE
4.) The angle of Polaris (the north star) above the horizon would not change on a flat Earth.
Polaris is the star that lies in space practically over the geographic North Pole of the earth.
If you stood at the North Pole, Polaris would be almost directly overhead.
Polaris

17. Why do observations of Polaris help determine the Earth’s shape?????
The North Star appears lower and lower in the sky as you travel toward the equator because of earth’s spherical shape.
At the North Pole, Polaris appears directly overhead.
At the Equator, Polaris appears at the horizon.
Polaris cannot be seen below the Equator in the Southern Hemisphere.

18. Ang OF POLARIS = LAT OF OBSERVER
Polaris Changes in Altitude – Polaris is a fixed point above the North Pole.
Because of this, in the Northern Hemisphere, the altitude (angle measured in degrees above the horizon) of Polaris tells observer his latitude position.
If observer’s latitude changes in the Northern Hemisphere, the altitude of Polaris will exactly match observer’s latitude.
Ang OF POLARIS = LAT OF OBSERVER
90º

20. Earth Facts…
The earth is approximately (7,922 mi)  diameter at the equatorial and (7,900 miles)diameter at the polar equatorial
The earth has a OBLATE SPHEROID shape
The total surface area is 510 Million sq kilometers
Water takes up 361 million sq kilometers (approx 70% )
Land takes up 149 million sq kilometers (approx 30%)
Tallest mountain from base to peak = Mauna Kea Hawaii 33,480 ft
Deepest point in the ocean = Challenger Deep in the Mariana Trench in the Western Pacific Ocean 35,840 ft deep
Age of the earth = 4.5 to 4.6 Billion years

21. What are the 4 big evidences for why we know the earth is NOT flat?
What is earths shape?

22. Atmosphere Hydrosphere Lithosphere Biosphere Earth's Layers
EARTH IS MADE UP OF A SERIES OF SPHERES HELD TOGETHER BY GRAVITY
ARRANGED FROM LOWEST TO HIGHEST DENSITY
Atmosphere
Hydrosphere
Lithosphere
Biosphere

23. ATMOSPHERE
The layer of gases that surrounds the earth above the surface Composed mainly of nitrogen and oxygen
Farthest from the earth’s center because it is the least dense
Stratified into layers or zones each with its own distinct Characteristics:
Troposphere
Stratosphere
Mesosphere
Thermosphere
Exosphere

24. The atmosphere is divided into five layers
The atmosphere is divided into five layers. It is thickest near the surface and thins out with height until it eventually merges with space.
The troposphere contains half of the Earth's atmosphere. Weather occurs in this layer. 
Many jet aircrafts fly in the stratosphere because it is very stable. Also, the ozone layer absorbs harmful rays from the Sun.
Meteors or rock fragments burn up in the mesosphere.
The thermosphere is a layer with auroras. It is also where the space shuttle orbits. 
The atmosphere merges into space in the extremely thin exosphere. This is the upper limit of our atmosphere.

26. Convection cycle Method of heat transfer in a fluid
Think lava lamp!
Cold is more dense = sinks
Hot is less dense = rises
This process results in circular convection cells
Also causes pressure gradients which create wind!
Also applies to the interior of the Earth

27. HYDROSPHERE
The layer of liquid water that lies between the atmosphere and most of the lithosphere
Covers approx 70% of earths surface
Average 3.8 Km thickness
Mostly hydrogen and Oxygen (H2O)

28. Crust Mantle Core GEOSPHERE
Below the atmosphere and ocean is the geosphere, it is not uniform so we split it into three main parts based on composition
Crust
Mantle
Core
Inner
outer

29. GEOSPHERE Most important sections to us…
Lithosphere – rigid outer layer of earth including crust and upper mantle
Continental Crust – part of the lithosphere is lese dense than the oceanic crust
Oceanic Crust – part of the lithosphere, is more dense than the continental crust
Asthenosphere – a weak layer of the mantle below the lithosphere where the rock is easily deformed. Magma flow CONVECTION CYCLES in this level is mainly responsible for plate tectonics.

30. Earth’s Layered Structure

31. Earth’s Magnetic Field
Geodynamo - The Earth’s magnetic field is produced by the geodynamo -Flow in the liquid iron outer core creates a magnetic field
Magnetic field - region affected by force emanating from a magnet - grows stronger as separating distance decreases - attracts or repels magnetically charged or moving electrically charged objects - compasses work because Earth is a large magnet

32. Northern & Southern Lights
Form because of our dipole magnetic field!

33. BIOSPHERE
The biosphere is all about life.-biosphere is our living world.
This is where all of the trees, bugs, and animals live. The biosphere extends to the upper areas of the atmosphere where birds and insects can be found. It also reaches deep into the ground at a dark cave or to the bottom of the ocean at hydrothermal vents.
The biosphere extends to any place that life (of any kind) can exist on Earth.

34. BIOSPHERE
The biosphere is the one place where all of the other spheres of the planet work together. Think about the interactions for a second. The land interacts with the water (hydrosphere). The land interacts with the air (atmosphere and climates). The land even interacts with forces deep inside the Earth and the energy coming to the Earth from space. All of those forces work together to create our living world.

35. End of Note Questions
What is the current theory for how earth was created?
Earths shape is most like a _______
List the four evidences that show earth is round.
Describe the atmosphere.
Describe the hydrosphere.
Describe the geosphere.
What 2 layers are we most interested in for this class?
Describe the biosphere.