# Earth's interior

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I have attached a PPT for you in order to answer these two questions. they must be answered from the power point not somewhere else!

1) List in order from the surface to the center the four main layers of the earth. Give their composition, thickness and how each behave (as a solid or liquid).

2) Subdivide the crust in to its two types and subdivide the mantle into its three main layers. For both the crust and the mantle, describe the composition and characteristics of each sublayer.

The Earth’s Interior How did we know that we have a layered planet? Density of the total planet 5.5 g / cm3 Density of the crust, mantle and hydrosphere 2.7 g / cm3 Water 1.0 g / cm3 Ocean Crust 2.9 g / cm3 http://earthquake.usgs.gov/image_glossary/images/crust.jpg How do we know what earth’s layers are made of, where they start and where they end? Direct Evidence: Rocks found at the surface; Rocks brought to the surface From below: Xenoliths, and Ophiolites From space: Meteorites Indirect Evidence Experiments: Diamond Anvil Gravity Studies Magnetic Studies Seismic Studies Most of our knowledge of Earth’s interior comes from seismic studies, that is the study of earthquake waves. Figure 12.1 Nuclear explosion or 1. Primary (P) waves What do they do to material as they travel through it? --> P Wave Animation Push-pull (compress and expand) Try the ribbon! Does this change the volume or the shape of the material? Changes volume only b) What type of material can P waves travel through? Try the balloons! What type of material can P Waves travel through? Solids? Does a solid have elasticity? When squeezed and released will it “rebound?” Liquids? Does a liquid have elasticity? When squeezed and released will it “rebound?” Gases ? Does a liquid have elasticity? When squeezed and released will it “rebound?” Solids? Yes Liquids? Yes Gases? Yes Secondary (S) Waves: What do they do to material as they travel through it? S Wave Animation The material is sheared. Does this change the volume? NO Does this change the shape? Yes, there is a temporarily change the shape of the material that transmits them. What type of material can S Waves travel through? (balloons!) Can S waves travel through Solids ? Yes When you attempt to change the shape of the water balloon and then release it, does it resist and rebound? Can S waves travel through Liquids? No Try changing the air-filled balloon shape. What happens? Does it resist and rebound? Can S waves go through Gases? No Which has a greater velocity, P or S? P wave travels 2000 km in 4 minutes = _____km/sec? 8.3 km/sec S wave travels 2000 km in 7 minutes= ____ km/sec? 4.76 km/sec P wave is faster. How many times faster? 8.3/4.76 ~~= 1.7 times faster Seismogram Seismic Wave Summary What we know so far….. *Compressional waves (P waves) can travel through liquids, solids, and gases. *Shear waves (S waves) travel through solids only. * P waves travel faster than S waves. What does the seismic wave path look like if the earth is homogeneous? Homogenous planet What happens to seismic waves when they travel from one type of material to another? Like light waves, they bend. Denser, more elastic rock Less dense, less elastic rock What happens to the density? It increases Elasticity increases too. Compact elastic materials transmit seismic waves best What can happen to the velocity with depth? It tends to increase with depth (more elastic). Denser, more elastic rock Less dense, less elastic rock What does the seismic wave path look like as it goes deeper into the earth? Think about Seismic Wave Summary ▪ Compressional waves (P waves) travel through liquids, solids, and gases. ▪ Shear waves (S waves) travel through solids only. ▪ P waves are ~1.7 times faster than S waves. ▪ Wave velocity tends to increase with depth due to pressure forming a more elastic material. ▪ Wave path is can bend (refract) at discontinuities, both major and minor. Seismic Wave Velocity Equations Depending on the angle that they hit, some waves go straight through. Some Waves reflect off of the surface too! How would these paths look in a layered earth? Any Volunteers? Layered structure. Who discovered a lot of this? I am the “Father of Seismology.” Andrija Mohorovičić THE CRUST: What do you know? Composition Ocean : Rock name & main elements Basalt, Rich in Fe-Mg Continental: Rock name & main elements Granite, Rich in Si-Al Physical properties Ocean Crust: Rigid and rocky Continental Crust: Rigid and rocky How about density?? Density of the crust, mantle, and hydrosphere 2.7 g / cm3 Water 1.0 g / cm3 Ocean Crust 2.9 g / cm3 3.3 g / cm3 http://earthquake.usgs.gov/image_glossary/images/crust.jpg Mantle Total planet is 5.5 g / cm3 How do we know there are layers of different density beneath the crust? Direct Evidence: Rocks found at the surface; Rocks brought to the surface From below: Xenoliths; ophiolites From space: Meteorites. Indirect Evidence Experiments: Diamond Anvil Gravity Studies Magnetic Studies Seismic Studies Density studies Discovery of the Mantle: 1909 Andrija Mohorovičić 6 km / sec 8 km / sec The Moho Mohorovičič Discontinuity How else do we know about the mantle? Rock Samples: Xenoliths & Ophiolites Meteorites: Chondrites Meteorite: Chondrite Contains olivine and pyroxene Xenolith Gabbro from an ophiolite How else do we know about the mantle? Experiments: Diamond Anvils Uwgd.edu What happens if the laser hits the diamond instead? The mantle is not homogeneous. Seismic tomography shows hot & cold areas in the mantle. The Mantle Peridotite: mainly olivine and pyroxene Kimberlite pipe Figure 12.12 At ~ 410 km At 660 Km: Spinel to Perovskite (Mg, Fe) (SiO3) The mantle is not homogeneous. ?? ?? The P Wave Shadow Zone: Discovery of the Core Mantle Boundary (1914) Beno Gutenberg The Discovery of the Core-Mantle Boundary Abrupt refraction suggests an entirely different material at 2,900 km depth Why do they bend inward? What does the P-Wave bend direction tell us about the outer core compared to the mantle? It is less elastic. The S-Wave Shadow Zone: More on the Core’s Physical properties Why would S waves disappear? Is the Entire Core Liquid? Discovery of the Outer Core-Inner Core Boundary Inge Lehmann Would P waves arrive sooner or later than if it was solid? Figure 12.10 Lehmann discontinuity The Effect of Temperature The Nebular Hypothesis Gravitational sorting The Core Density is 11 g /cm3 Composition: 95% Fe + 5% Ni Figure 12.C Outer core gives Earth's magnetic field, which effectively extends several tens of thousands of kilometers into space, is called the magnetosphere This force acts like a shield, protecting the Earth from solar charged particles that would destroy the atmosphere. Do the Particles Sneak Through? How strong are the Earth’s Magnetic Currents? Do they change in strength? Do they change in direction? South Atlantic Anomaly Four defining layers by Composition: 1. Crust 2. Mantle 3. Outer Core 4. Inner Core Defining layers Physical Properties: 1. Lithosphererocky 2.Asthenosphereflows (partly melted) 3. Mesopheresolid &flows 4.Outer Coremolten 5. Inner Coresolid

MrFifth
School: Rice University

EARTH'S INTERIOR
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EARTH'S INTERIOR

1) List in order from the surface to the center the four main layers of the earth. Give
their composition, thickness and how each behave (as a solid or liquid).

A. The Crust
The crust is the first layer of the earth which is subdivided into two
types namely the Oceanic crust and the Continental crust. It is constantly
movi...

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Anonymous
Totally impressed with results!! :-)

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