Earth Systems 3209

1. Earth Systems 3209 Reference: Chapters 1, 17 and Appendix A Unit: 1 Introduction to Earth Science –The Evolution of Planet Earth

2. Unit 1: Topic 2.3 Formation of Earth (Geosphere) Focus on . . . • describing how Earth (Geosphere) segregated into layers. • identifying that segregation was influenced by radioactive decay, collision of particles, gravity and density.

3. Solar Nebula Hypothesis: Overview • To understand the origin of Earth, we must focus on how Earth formed billions of years ago. Earth formed as a direct result of the“Solar Nebula Hypothesis”, which states, “a great cloud of gas and dust shrank under its own gravitation and transformed into the planets and natural satellites that make up the present solar system” Text Reference:pages 19 – 20

4. Early Earth • It is thought that Earth was not always layered as it is today • Some scientist suggest that Earth was a lot like the moon in appearance billions of years ago • The composition of the ancient Earth was thought to be the same throughout. It separated later in Earth’s history

5. Segregation of Earth (Geosphere) • Shortly after Earth formed, the interior segregated and took on a layered structure • Heat generated from the collision of particles and the decay of radioactive isotopesproduced heat and was responsible for melting Earth’s interior

6. Segregation of Earth (Geosphere) • Gravitation caused great streams of hot heavy liquidsto move toward Earth’s center and melted the lighter rock material forcing it to the surface • This sorting of material by density early in Earth’s history, is still occurring today, but on a smaller scale • Gases are released from Earth’s interior through volcanoes

7. Segregation of Earth (Geosphere) Inner Core Crust Outer Core Mantle • The heavier material (nickel and iron) which concentrated close to Earth’s center formed the inner and outer core • The lighter and less dense material which moved upwards closer to the surface formed Earth’s crust • The material in between formed earth’s mantle and continues to separate today

8. Segregation of Earth (Geosphere) Atmosphere Hydrosphere Geosphere • Atmosphere and oceans formed as a result of the gases given off by volcanic out gassing throughout Earth’s history • This will be discussed in another presentation

9. Example 1: Which factors were most responsible for the segregation of Earth into layers? Earth’s rotation, meteorite impact, radioactive decay Earth’s rotation, volcanic outgassing, density gravity, volcanic outgassing, meteorite impact gravity, radioactive decay, density

10. Example 2: What is thought to be the primary reason for Earth’s internal temperature remaining higher than expected? friction caused by the rubbing of plates gravitational pull from the moon increasing sedimentary layers on the surface radioactive decay of unstable elements

11. Your Turn . . . Take the time and complete the following question . . .(Solution to follow) Questions: How does the solar nebular hypothesis explain the segregation of the geosphere into layers?

12. Solutions . . . Questions: How does the solar nebular hypothesis explain the segregation of the geosphere into layers? NOTE: Be sure to “refer to page 19 - 20 in text. Second paragraph top left of!! • Billions of years ago, the decay of radioactive elements coupled with heat generated by the colliding of particles, caused Earth’s interior to melt. • This allowed a differentiation of Earth’s interior based on density. • The denser elements, nickel and iron, would sink to the interior while the lighter rocky components (silicates) floated toward the surface. • This segregation by density is thought to still occur today on a smaller scale and was responsible for the apparent layering of Earth’s interior into layers of material with different physical properties.

13. Additional Question and Solution: Describe the process that could lead to the segregation of layers within a newly-formed planet.? A newly-formed planet would have a homogeneous solid interior that is the same throughout. Over time the planet would experience numerous impacts from meteoroids and asteroids. This would cause the particles within the planet to collide and heat up as a result of friction. In addition, heat may result when radioactive elements, common in space rocks, decay to become stable elements. The resulting heat would build up within the planet and eventually cause the interior to melt. Heavier, more dense elements would move toward the center of the planet and the lighter, less dense elements would move toward the surface of the planet. This process would continue for extended periods of time and result in the planet becoming segregated into layers according to the density of the material that makes up the planet.

14. Summary . . . Overview of Points covered: • When describing how Earth segregated, include the following main points: • Primitive Earth was one homogeneous solid sphere. • Interior heated up and melted as a result of;1) collision of particles and 2) decay of radioactive elements. • Gravity caused the more dense materials (nickel and iron) to move toward the center of Earth which formed the inner and outer cores. • Lighter materials (silicates) were forces toward the surface and formed the crust. • Material in between formed a layer called the mantle. This layer is still segregating today. • Throughout the segregation process, volcanic gases escaped which eventually formed the atmosphere and the hydrosphere.