Formation of Planets and Earth Structure. Big Bang Theory. What is the shape of our solar system?

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Pamela James
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Formation of Planets and Earth Structure From work of Einstein and Hubble Big Bang Theory ~14 Ga All matter in one point Exploded Expanding still Food for thought What is the shape of our solar

1 Formation of Planets and Earth Structure From work of Einstein and Hubble Big Bang Theory ~14 Ga All matter in one point Exploded Expanding still Food for thought What is the shape of our solar system? A. Spherical (3-D): the Sun is in the center, the planets orbit in spherical shells. B. Disc shaped (3-D): fat in the center, tapering to planar at the edges. Sun in the middle. C. Planar ellipse (oval) that is almost circular (2-D) Top view Edge view 1

Consider H2O and the planets. Which of the following is correct? A.

H2O was not originally present when the Earth formed, and was added to the Earth early in it s history.

Gasses (moslty H and He) compress into dense balls = Star Heat by compression to > 1x106 K Fuse heavier

2 Consider H2O and the planets. Which of the following is correct? A. Earth is the only planet with H2O on the surface. B. Most of Earth s H2O is in the oceans. C. H2O was not originally present when the Earth formed, and was added to the Earth early in it s history. Nebular Theory and formation of solar systems Clouds of gas/matter contract under the force of gravity. Gasses (moslty H and He) compress into dense balls = Star Heat by compression to > 1x106 K Fuse heavier elements Emit light and HEAT Supernova = exploded star Repeat process A super nova Crab Nebula Nebular Theory Look at the shape of these galaxies (not nebulae, but pretend) Draw nebular theory 2

3 How a super nova becomes a solar system Terrestrial vs. Gaseous Planets Accretion of Terrestrial Planets Mercury, Venus, Earth, Mars + Asteroid belt Close to sun - HOT during accretion Only refractory compounds are solid Solar wind blows light particles away Planets too small to retain light elements 3

Accretion of Jovian Planets Jupiter, Saturn, Uranus, Neptune (not Pluto) Retention and accumulation of volatile compounds Condense in cooler

70% of Earth is covered with water. Problem: no water in the region of space where Earth formed.

Heterogeneous Accretion: Some meteorites that collided with Earth near the end of its formation had ~18 wt% H2O locked up in minerals - this is

4 Accretion of Jovian Planets Jupiter, Saturn, Uranus, Neptune (not Pluto) Retention and accumulation of volatile compounds Condense in cooler region - volatile compounds are solid Big Planets can hold light elements (H, He) during solar wind Where does water on Earth come from? 70% of Earth is covered with water. Problem: no water in the region of space where Earth formed. So, the material Earth formed from shouldn t have contained water. Heterogeneous Accretion: Some meteorites that collided with Earth near the end of its formation had ~18 wt% H2O locked up in minerals - this is structural water, not free molecular water. So, Earth s water has been added (1) during accretion, and (2) after formation Where does the water on Earth come from? Planetesimals from beyond the snow line (meteorites) added water to Earth! Note, comets were not a major source of Earth s water. 4

5 Relationships between planets: Why do the Inner Planets have lower mass than outer planets? A. They have greater density B. They formed in a region where the solar wind was strong. C. They formed in a region where temperatures were cold. Relationships between planets: Why do the Outer Planets have lower density than inner planets? A. They have greater mass B. They formed in a region where the solar wind was strong. C. They formed in a region where temperatures were cold. Origin of Earth s Water 5

6 Origin of Earth s Core, and Mantle Origin of Earth s Moon 6

7 Origin of the Moon! Let s watch a summary of what we know Then, let s look at Earth s Structure Topography of the Earth: Why are oceans deep? This is a fundamental observation about the Earth that hints at it s structure There is something fundamentally different between Ocean Crust and Continents! The Hypsometric Curve Continental Crust Ocean crust 7

8 Draw Earth s Structure 1. Composition layers 2. Mechanical layers Composition vs. Mechanical layers of the Earth 8

Now we can understand hypsometric curve Ocean floor is deeper than continents because Ocean lithosphere is thinner than continental lithosphere Oceanic lithosphere is denser than continental

9 Now we can understand hypsometric curve Ocean floor is deeper than continents because Ocean lithosphere is thinner than continental lithosphere Oceanic lithosphere is denser than continental lithosphere Thus, due to relative buoyancy the oceanic lithosphere does not ride as high on the asthenosphere compared to the continental lithosphere. This is the concept of isostacy concept of isostacy Continental lithosphere sinks deeper and rides higher than oceanic lithosphere due to it s thickness and lower density. In this picture the thick board represents the continental lithosphere. The thinner boards represent the oceanic lithosphere. Note, if you remove the top of a continent, it bobs up above the oceanic lithosphere. Isostasy: Buoyancy Model What will happen if the thickness of the block (Z A ) is increased? A. The base of the block will sink deeper. B. The top of the block will rise higher C. Both A and B D. Nothing will happen, the position of the block will not change. Z U Z A Z B model 9

10 Archimedes Principle More Examples of Isostasy: Thick ice sinks deeper and rides higher than thin ice More Isostasy: Glacial isostatic rebound 10

Now we understand this graph! Why are the oceans deep relative to the continental surfaces? A. The ocean water weighs down on the oceanic crust, causing it to sink into the mantle. B.

11 Now we understand this graph! Why are the oceans deep relative to the continental surfaces? A. The ocean water weighs down on the oceanic crust, causing it to sink into the mantle. B. Ice at high latitude on the continents lifts the low-latitudes up like a teeter-totter. C. The continental lithosphere is thicker than the oceanic lithosphere. D. The oceanic crust is thin, so it floats lower on the mantle Review questions 1. How does temperature vary across the solar system? 2. How does planet size and density change with distance from the sun? 3. What caused the variation in planet size and density? 11

12 Review questions How did the Moon form? How does the Moon differ from the Earth (size, mass, density, structure)? When did the moon form? Review questions What does the hypsometric curve tell us about the Earth? How is the continental lithosphere different from the oceanic lithosphere What does the lithosphere float on? Continental Crust Ocean Crust Review questions What are the four elements that compose 90% of the Earth? What are the composition layers of the Earth? Where is most of Earth s water stored? Compare and contrast the Lithosphere and the Mantle. Compare and contrast the Lithosphere and the Asthenosphere. Compare and contrast the Lithosphere and the Crust. What is Isostacy and how does it explain elevated continents and deep oceans? 12

Nebular Hypothesis and Origin of Earth s Water

Nebular Hypothesis and Origin of Earth s Water What is the shape of our solar system? A. Spherical: the Sun is in the center, the planets orbit in spherical shells. B. Disc shaped: fat in the center, tapering