Earth’s Structure & Motion

1. Earth’s Structure & Motion Chapter 4.1: Earth’s Formation

2. Key Idea • Earth formed from a whirling cloud of gas and debris into a multilayered sphere, which has since been losing heat.

3. Geology • The study of the planet Earth: • It’s structure • Composition • How it has changed over time • The Earth as we know it is the result of changes that have occurred over billions of years (It didn’t get like this over night)

4. Origin of the Solar System • Nebular Hypothesis (most widely accepted) • About 4.6 billion years ago…. • A large cloud of gas and dust began rotating slowly in space • As time passed, the cloud shrank under the pull of its own gravity. The rate of rotation increased as it shrank • Most of the material in the cloud gathered around the center • The compression of the material made its interior so hot  hydrogen fusion occurred • Result: the sun and planetismals were born • Over time: nearly all of the material from the original cloud became orbiting planets as well • See: Origin of Solar System Animation

5. Earth’s Size and Shape • Earth is not a perfect sphere – oblate spheroid • Sphere that bulges in the center • Cause: the spinning motion of the Earth • How do scientists know this? • They can measure the weight (in Newtons) of an object at several places on the Earth’s surface • Recall: the weight of an object, in Newtons, is the force with which gravity pulls an object toward the center of the Earth • The further an object is from the center, the lighter it is, and the closer, the heavier it is

6. Example of Scientific Evidence • An object at the North or South Poles weighs 195 Newtons • At the equator, that same object weight 194 Newtons • What does this evidence tell you? • An object is closer to the Earth’s center at the poles than the equator • If Earth were a perfect sphere  an object would be the same distance from the center at ALL points and so would the object’s weight!!!

7. Quick Facts About Earth • 29% land or 149 million square miles • 71% water or 361 million square miles • Earth’s original surface was very similar to the surface of the moon • Earth was most likely composed of the same material from the surface all the way to the center

9. Layers of the Earth

10. Science Burrito Lab Follow Up • Video Wrap Up

11. Earth’s Heat • Events that formed Earth produced heat • Heat came from: • Meteorite impacts • Weight of overlying materials caused compression in Earth’s interior • Decay of radioactive isotopes

12. Earth Has Been Slowly Losing Heat • Reasons: • Some rocks lose heat more quickly than others • The thickness of the crustal rock varies from place to place • The percentage of radioactive materials in rocks varies

13. Earth’s Magnetic Field • Earth’s Magnetic Field • Imagine a bar magnetic inside the Earth tilted 11 degrees away from the poles • The field is the resulting lines of force that loop from one end of the bar magnet to the other • 11 degree tilt explains why the magnetic north pole and geographic north pole are not in exactly the same place • North end = attracting = • positive end • South end = repelling = • negative end