Into Which Layer Have We Drilled? Evidence of Earth s Interior Direct and Indirect Evidence 1. Crust 2. Mantle 3. Outer Core 4. Inner Core Why?? How Many Types of Crust Exist? Which of the following is the Continental Crust? 1. One 2. Two 3. Three 4. Four What Are They?? How Do You Know??
Which of the Following Best Describes a Xenolith? 1. Magma rising to the surface from the outer core. 2. Magma rising to the surface from the mantle. 3. Pieces of unmelted rock rising to the surface from the outer core. 4. Pieces of unmelted rock rising to the surface from the mantle. Why are they Important? Examples of Xenoliths Peridotite What Causes Earth s Magnetic Field? How Do You Make A Magnetic Field? Moving electrons can create a magnetic field! 1. Large, solid bar magnet in center of the Earth. 2. Molten rock rotating in Earth s interior. 3. Liquid iron rotating in Earth s interior. 4. Scientists still don t know. Which Layer Creates the Magnetic Field? The material inside the coil, known as the core material, affects the strength of the magnet. The best material for making a strong electromagnet is???
Why A Liquid?? When solid iron gets above the Curie point, it no longer will be magnetized. Curie Point = 770 C = 1043 K The only way to create a field inside the Earth would be to have moving electrons! The rotation of the Earth causes the liquid to move, creating the electric current needed to make the magnetic field. Think About Density! The average density of Earth is 5.5 g/cm 3. The surface rocks have a density of about 2.8 g/cm 3. From this, scientists can infer that the core of the Earth is 1. Scientists still don t know. 2. Made of a material that is more dense than the surface rocks. 3. Made of a material that is less dense than surface rocks. 4. Made of similar rocks as the surface. What Type of Material Could It Be?? P- and S-waves In 2008, scientists published a study indicating that they detected a seismic wave known as the PKJKP wave. This wave travels as a P-wave through the outer core. It turns into an S-wave at the outer-inner core boundary. Travels through the inner core as an S-wave. Then turns back into a P-wave when it re-enters the outer core. Revise Your Model! Use all of the evidence that you have explored to improve your model of Earth s interior. Your model should include the following: 1. An image of what you believe the interior of the Earth looks like if you were to slice it in half. Layer Thickness State of Matter 2. An explanation of your image including why it looks like this. 3. The evidence scientists have for this structure. Your model should be both qualitative and quantitative!
Revise Your Model! Who Is Right? Your model should include the following: 1. An image of what you believe the interior of the Earth looks like if you were to slice it in half. Layer Thickness State of Matter Composition Density 2. An explanation of your image including why it looks like this. 3. The evidence scientists have for this structure. Your model should be both qualitative and quantitative! Rudy: Lizette: Zara: Mateo: Haliaka: Your Task Write a caption for each of these tables. What does this mean?
Why Is There A Discrepancy? Absolute Age Dating For age dating to be accurate, the mineral that is being analyzed must be a closed system. A closed system refers to a mineral that has not gained or lost any parent or daughter atoms during all the different processes that have occurred to the rock. What Does Our Density Data Tell Us About Early Earth? Summary Table Period 6 Period 7 Period 8 Earth s Formation
How Was Earth Formed? There are different theories for how planets form. The main theory is known as the core accretion model. Remaining nebula material clumped together by gravity into larger particles. Solar wind created when the Sun formed blew lighter elements to outer regions of solar system. What Is Accretion? Accretion is the growth of an objecting by the sticking together of particles. Scientists believe accretion was initially rapid, with collisions frequent. As objects got bigger, the process would slow down, and could take millions of years. When reached moon-size or Mars-size, pretty isolated and growth stops. Is it Hot in Here? The impacts that occurred during accretion would create lots of heat. As the Earth got larger, the gravity caused it to compact, which also caused it to heat up. Radioactive elements within the Earth decayed, releasing heat.
Planetary Differentiation Accretion would create an Earth that was uniform in composition. Feedback Loops When a system undergoes a change, how much they change is dependent on the type of feedback mechanism that exists. When the interior became hot enough, everything melted, including the iron. Denser elements began to sink down toward the core, while less dense materials rose to the surface. Negative Feedback - System changes to minimize change and bring things back to a balance. Positive Feedback - System changes to enhance the change. Which Is It? Early Earth s Feedback Loop Earth materials partially melt Negative Feedback Positive Feedback? Denser materials sink More materials melt + Sinking produces heat Temperatures increase
Why Are There Layers? Much of Earth would have melted during the differentiation process, which would cause the materials to sort themselves out by density. Lots of Planets! The core accretion model works really well to explain the formation of the terrestrial planets. It doesn t explain the formation of the gas giants as well! Other theories are being explored! Let s Look At The Rest of The Rocks!