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Layers of the Earth Notes

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1 Layers of the Earth Notes
Taken from: Article from Cate ‘ O Donnell 2012

2 Introduction Scientists have only understood the composition of the Earth for about the past 100 years. It wasn’t until the modern seismograph was invented that they had the tools to explore the different layers of the Earth. (A seismograph is a device used by scientists to study earthquakes.)

3 Main Layers The Earth is made of 3 basic layers: Crust Mantle Core

4 The Crust The crust is the least dense, thinnest and outermost layer of the Earth. The Earth’s rocky outer curst solidified billions of years ago, soon after the Earth formed. It is made of oxygen, silicon, aluminum.

5 The Crust Types of Crust Layer Description Density Composition
Location Continental Crust Makes islands and continents Older Less dense when compared to oceanic crust Has less amount of iron, calcium, and magnesium Less dense granite kilometers (Thick) Oceanic Crust Found under the ocean Younger Dense when compared to continental crust Has twice as much iron, calcium, and magnesium More dense basalt 5-10 kilometers (Thin)

6 The Crust This crust is not a solid shell. It is broken up into huge, thick crustal or tectonic or lithospheric plates that drift on top of the soft, underlying mantle. This layer where you see plates is called lithosphere.

7 The Mantle The mantle is the layer of Earth between crust and the core. It is over 20,000 kilometers deep and makes up most of the Earth’s mass. It has more magnesium and less aluminum and silicon than the crust. The mantle is denser than the crust. (Humans have never been to the mantle, but a group of scientists in the middle of the Pacific are trying to change that. They are planning on drilling a hole into the thinnest part of the crust under the ocean. This complicated endeavor will involve six mile long drilling pipes and drill bits that have to be changed every fifty hours. It is estimated that the project could reach the mantle in the early 2020s.)

8 Mantle Layers Upper Mantle Or Aesthenosphere Physical state of Matter
Liquid magma Lower Mantle Mesosphere Solid rock

9 Convection Currents: Because the core is so hot, a current of heat flows from the core to the crust. These currents are called convection currents. Convection currents take place in the mantle. Convection currents cool down as they come closer to the surface of the Earth. The rising of the current stops and it travels in a horizontal direction along the bottom of the crust. When the current cools down more, it falls back towards the core. There, the temperature increases and the current rises again. This process goes on and on.

10 The Core Composition Thickness State of Matter and
Composition Thickness State of Matter and Reason for state of matter Outer Core iron, nickel, sulfur, and oxygen about kilometers thick Liquid Because they have melted in the intense heat of the outer core Inner Core mainly of iron and nickel around kilometers thick Solid Because of the high pressure exerted on them by the outer layers of the Earth

11 The Core (The outer core was discovered by seismologist Inge Lehmann from Denmark. A seismologist is a person who studies earthquakes. By looking at the way earthquake waves moved through the Earth, Lehmann was able to determine that the outer core was liquid.) Seismic waves move much more slowly through liquids than solid rocks. They are also reflected instead of moving in a straight line as they do through solid materials.

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