The Earth Moon System

1. The Earth Moon System Formation, Development, and Current State

2. We were wrong… • It was once believed that Earth was created, instantly, 6000 years ago. • Ancient thinkers like Aristotle and Leonardo da Vinci saw fossils as evidence the Earth was much older. • Lord Kelvin used heat to determine an age of 24-400 million years old • Arthur Holmes was the first to get a near accurate age of the Earth using, determining the earth to be about 1.6byo using radioactive decay. • Later, improved methods of radiometric dating led to a much more accurate age of the Earth.

3. Formation • About 4.5 billion years ago, Earth, along with the other planets in our solar system began to take shape. • They formed in accretion disks. • The material that formed the Earth was created in supernovas.

4. Proto-Earth • Within 10-20 million years Earth, slightly smaller than today, had formed from the accretion disk located about 150,000,000km from the sun. • It is hypothesized that another, even smaller planet was also forming at about the same distance. • This planet, Theia, was about the size of Mars.

5. Giant Impact Hypothesis • Shortly after the formation of these two planets, Theia struck Earth with a glancing blow. • This impact liquefied Earth and ejected a large amount of molten material. • The ejected material formed the Moon. • The remainder of Theia sunk to the center of Earth to help form its iron core. • http://upload.wikimedia.org/wikipedia/commons/d/d1/Big_Slash.gif • There are some other, less likely idea’s as to how the Moon formed

7. Co-Formation Hypothesis • Before, we visited the Moon and were able to analyze its contents, it was thought that the Moon formed at the same time and location as Earth. • This would have left the Moon rotating directly above the equator with much more Iron than it currently has.

8. Fission Hypothesis • It was also once believed that centrifugal forces pulled a chunk of earth out into space leaving a basin behind which later formed the Pacific Ocean. • This would have required the Earth to be spinning much faster than it does today. • It also would have formed the Moon rotating directly above the Equator. • These facts make this an unlikely hypothesis.

9. Capture Hypothesis • Because the Moon’s orbit is not directly above the equator, it was once believed that the moon was formed elsewhere in the Solar System and later captured by Earth’s gravity. • For this to have occurred the Earth would have needed a much larger atmosphere to slow down the approaching Moon. • This too is very unlikely.

10. Explanation • The Giant impact Hypothesis is the most likely because it helps explain other features about the Earth Moon system. • Large amount of Iron in the core • Still molten mantle • Tilt of the Earth • Speed of Rotation of Earth

11. A Changing Planet Time Line • 4.5 bya - Magma Earth • 4.4bya - Ocean Earth • Carbon dioxide atmosphere, iron rich oceans • 3.4bya - Continents form • Granite floats on magma • 2.2-1.5bya - Blue Planet • Stromatolites release oxygen that turns oceans and sky blue.

12. Time Line (cont) • 1.0bya Rodinia • Super-continent • Trilobites best evidence • 700mya Snowball Earth • Caused by massive super-continent • 630mya Cambrian Explosion • Shallow seas allows for evolution of a wide variety of life • Evidence found in Burgess Shale

13. Time Line (cont) • 300mya - Animals/Plants moved on land • Oxygen in atmosphere created ozone that protected animals and plants from UV rays • 250mya - Massive volcanic eruptions • Led to extinction of 95% of living things • Creation of Pangea • 235mya - Dinosaurs began to rule • “Lukewarm” blooded, allowed them to survive in hot, oxygen rich environment.

14. Time Line (cont) • 180mya - Pangea breaks up. • Dinosaurs survive • 65mya - KT Boundary • Asteroid/Comet impacts Mexico • Volcanoes erupting in India • Most dinosaurs go extinct

15. Time Line (cont) • 50mya - Mammals began to flourish • Uplift and Erosion shape surface of Earth • 2mya - Human ancestors leave Africa • Ice Ages send glaciers back and forth across the continents • 10,000ya - Last Ice Age retreats • Human civilization begins

16. The Future • +15000y - New Ice Age • Within the next 15000 years a new Ice Age will begin. • +200my - New Super-Continent forms • +2by - Mantle and Core cool • Stops tectonic movement • Stops magnetic field

17. Earth • Earth is the 5th largest planet. • 12,800km diameter. • Not a perfect sphere • Centrifugal force makes the circumference around equator bigger than circumference around poles. (difference of 67km) • Oblique Spheroid

18. Earth’s Axis • Earths axis is an imaginary line that runs through the Geographic North and South Poles. • The Earth spins about this axis once every 23hours 56minutes. • The axis is tilted at an angle of 23.5º from vertical. • This tilt is responsible for the seasons.

19. Seasons • The seasons have differing weather patterns for two reasons • 1. The angle of the Sun’s rays varies from most direct in the summer (hotter) to least direct in the winter (cooler) • 2. The length of day varies from longest in the summer to shortest in the winter, giving the Sun’s rays less time to warm the Earth. • The Northern and Southern Hemispheres have opposite seasons.

21. Solstices • The solstices occur on when the amount of daylight is the greatest or least and the angle of the Sun’s Rays are the most or least direct. • Winter Solstice - December 21st • Summer Solstice - June 21st

24. Equinoxes • An equinox occurs when there is exactly 12hours of daylight and the Sun’s rays are pointing directly at the equator. • Spring Equinox - March 21st • Fall Equinox - September 23rd

26. Earth’s Structure • Earth is comprised of several layers. • These layers are separated due to their density. • Crust • Upper Mantle • Lower Mantle • Outer Core • Inner Core

28. Crust • The Crust is the layer of the Earth we all walk on. • 0-35km below the surface of the Earth. • Two different types • Granite Crust - Covers continents, thicker • Basaltic Crust - Ocean Floor, thinner • Crust contains rock in all phases of the rock cycle.

29. Mantle • The Mantle is the area of rock between the core and the crust. (35-3000km) • The rock is plastic in characteristic and flows too slowly to be considered a liquid. • The difference between the upper and lower mantle is due to the way seismic vibrations pass through. • Seems to be pressure related.

30. Outer Core • Liquid layer of Iron and Nickel located between the inner core and the lower mantle. • 3000-5000km deep • Predominantly responsible for Earth’s magnetic field due to the rapid movement of the liquid metal.

31. Inner Core • The center of the Earth. • Solid alloy of nickel and iron. • 5000-6400km deep • Thought to be hotter than the surface of the sun. (Remains solid due to immense pressure)

32. Earth’s Magnetic Field • As a result of the rapidly spinning liquid metal found in the outer core, Earth has a magnetic field, similar to a giant bar magnet. • This magnetic field protects us from harmful rays and particles emitted from the sun.

36. Magnetic Poles • Just like a bar magnet, Earth has magnetic north and south poles. • A compass is a small magnet that aligns its self to Earths magnetic field, always pointing to the North and South Magnetic Poles. • A compass above either magnetic pole will point in random directions. • These poles do not align with Geographic poles. • They can move up to 15km a year.

37. The Moon • The Moon is Earth’s only natural satellite. • It is the fifth largest moon in the Solar System. • The Moon’s orbit ranges from a distance 363,000km to 406,000km. • The moon is about 3500km in diameter • This gives the moon roughly 1/6th the gravity of here on Earth.

38. Moon (cont) • The moon takes 27.3 days to orbit the Earth. • As the Earth is also moving during this time the Moon completes its cycle of phases over a period of 29.5 days.

39. Structure of the Moon • Like Earth, the Moon has a crust, mantle and core. • Unlike Earth, only a small portion of the Moon’s core is still liquid. • The Moon has cooled significantly since it was formed.

41. Surface of the Moon • The Moon’s surface has several important features. • Maria - dark, relatively featureless plains on the moon. • Formed as lava filled depressions left by impacts. • Terre - Lighter colored highlands of the moon • Mountains exist only around the edges of Maria and were not formed by tectonic movement.

42. Surface of the Moon (cont) • Regolith - the “soil” of the Moon • Result of many impacts breaking up rock into very fine particles. • Maria has 3-5m of regolith, Terre has 10-20m. • Impact Craters - form as asteroids, meteors, and comets impact the Moon. • Lack of atmosphere leaves these craters undisturbed.

44. Motion of the Moon • If we could view the Earth moon system from above the North Pole, the moon would rotate around the Earth counterclockwise. • It also rotates once about its axis, again in a counterclockwise motion.

46. Tides • One of the most obvious effects of the relationship between the Moon and Earth are tides. • Tides are the result of the gravitational pull of the Moon and the Sun on Earth’s oceans. • They can cause the level of the ocean to change as much as 17 meters depending on the location

48. Types • There are two types of tides. • Spring tides occur when the Moon, Earth and Sun form a straight line. • These tides are the most extreme, highest and lowest. • Gravity of Sun and Moon work together. • Neap tides occur when the Moon, Earth, and Sun form a right angle. • These tides have the least variation between high and low tide. • Gravity of Sun and Moon are work against each other.