Forces Within. Earth s Layers Continental Drift Seafloor Spreading Plate Tectonics

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1 Forces Within Earth s Layers Continental Drift Seafloor Spreading Plate Tectonics

2 I have a QUESTION for YOU! How does an apple compare to Earth?

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4 Earth s Internal Structure

5 Objectives At the end of this unit you will be able to Describe Earth s internal structure based on composition and physical behavior. Explain the composition of Earth s interior.

6 Essential Questions At the end of this unit, you will be able to answer the following questions. What are the layers of Earth? How are each of Earth s layers different in composition and physical behavior? What process causes the movement of the lithospheric plates and how does it work?

7 Crust The thin rocky, outer layer of Earth. Divided into oceanic and continental crust. Corteza

8 Mantle A solid rocky shell that is the largest layer of Earth. Manto

9 Core The center of Earth. A sphere composed of an iron-nickel alloy. Divided into an inner core and an outer core. Núcleo

10 Lithosphere Earth s outermost layer consisting of the crust and the upper mantle. Solid and rigid. Litosfera

11 Asthenosphere Located below the lithosphere. Also called the convecting mantle. Plastic-like and flowing. Astenosfera

12 Lithospheric Plates The crust of the Earth is broken into many pieces called lithospheric plates. The plates "float" on the soft, semi-rigid asthenosphere.

13 Key Concepts Earth is divided into zones and layers based on chemical composition and physical properties. Earth s interior consists of three major zones defined by its chemical composition and density the crust, mantle and core. Earth can be divided into four layers based on physical properties such as temperature, pressure, strength and ability to flow. Knowledge of both types of layers is essential to an understanding of our planet.

14 Key Concepts Earth s four layers (based on physical properties) are the lithosphere, mantle (asthenosphere and lower mantle) inner core and outer core. The crust earth s relatively thin, rocky outer layer is of two different types continental crust and oceanic crust. Each type of crust varies by composition, density and age. The continental crust is made of lighter, granitic rocks. The average density of continental rocks is about 2.7 g/cm 3. Age over 4 billion years. The crust of the ocean floor is composed of basalt. The average density of oceanic rocks is about 3.0 g/cm 3. Age 180 million years or less.

15 Key Concepts Earth s mantle is the largest layer. More than 82% of Earth s volume is contained in the mantle. Earth s mantle is composed primarily of dense pyroxene and peridotite. The upper mantle can be divided into two different parts the lithosphere and the asthenosphere. The lithosphere consists of the entire crust and the uppermost mantle, and forms Earth s relatively cool, rigid outer shell.

16 Key Concepts The asthenosphere is a soft, comparatively weak layer. Due to the temperature and pressure, a small amount of melting occurs. Earth s core is thought to be composed mainly of a very dense iron-nickel alloy. The average density of the core is 11 gm/cm 3. The core is divided into two regions the outer core and the inner core. The outer core is a liquid layer. Movement of this layer generates Earth s magnetic field. The inner core is solid due to the immense pressures found at the center of the planet.

17 Earth s Layers Composition vs Behavior Earth can be divide into layers based on two different characteristics composition and physical properties (behavior). Compositionally, Earth has three layers the crust, the mantle and the core. The core is the most dense and the crust is the least dense due to the different materials making up each of these layers. Earth s interior can also be divided into four layers based on physical properties and behavior. The lithosphere is very rigid, while the asthenosphere is much more weak. The core is divided into two parts based on whether it is liquid or solid.

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19 Composition ~ Crust, Mantle and Core The Earth is composed of three different layers based on composition. The CRUST is the layer that you live on, and it is the most widely studied and understood. Made of granite and basalt. The MANTLE is much hotter and has the ability to flow. It is divided into the upper and lower mantle. Made of peridotite. The CORE is divided into the outer core and the inner core which are even hotter than the mantle and, with pressures so great you would be squeezed into a ball smaller than a marble if you were able to go to the center of the Earth! Made of iron-nickel alloy.

20 The Crust The Earth's Crust is like the skin of an apple. It is very thin in comparison to the other three layers. The continental crust is about 25 miles (32 km) thick under the continents. Composed of granite. Density 2.7 g/cm 3. The oceanic crust is only about 3-5 miles (8 km) thick. Composed of basalt. Density 3.0 g/cm 3.

21 The Crust The crust is composed of two rocks. The continental crust is mostly granite. The oceanic crust is basalt. Basalt is much denser than the granite. Because of this the less dense continents ride on the denser oceanic plates.

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23 The Mantle The Mantle is the largest layer of the Earth. 82% of Earth s volume is contained in the mantle. The mantle is composed of a very dense rock called peridotite. The upper part of the mantle is very rigid. Below this layer of rigid rock, the mantle is composed of very hot, dense, plastic-like rock that flows.

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25 The Core The Core is like a ball of very hot metals. The composition of the core is thought to be an iron-nickel alloy, with minor amounts of oxygen, silicon and sulfur elements that readily for compounds with iron. The average density of the core is about 11 g/cm 3. It is the movement of the liquid outer core that creates Earth s magnetic field.

26 Physical Properties Lithosphere, Asthenosphere, Outer Core and Inner Core The Earth is composed of four different layers based on physical properties and behavior. The LITHOSPHERE is made up of the entire crust and the uppermost mantle. This layer is very rigid and brittle. The ASTHENOSPHERE is much hotter and has the ability to flow. The top part of the asthenosphere has temperatures and pressures that result in a small amount of melting, creating a weak zone. Within this weak zone, the asthenosphere and the lithosphere are mechanically detached. The result is that the lithosphere is able to move independently of the asthenosphere. The OUTER CORE is liquid and flows. The INNER CORE, while at a higher temperature than the inner core, is solid due to the immense pressure found at the center of Earth

27 The Lithosphere The crust and the upper layer of the mantle together make up a zone of rigid, brittle rock called the Lithosphere.

28 Lithospheric Plates The lithosphere is broken into many pieces called lithospheric plates. The plates "float" on the soft, semi-rigid asthenosphere.

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30 The Asthenosphere The asthenosphere is the semi-rigid part of the mantle. The movement of the plastic-like asthenosphere is the reason that the crustal plates of the Earth move.

31 Asthenosphere Mantle Lithosphere Cool mantle sinks Hot mantle rises

32 The Outer Core The outer core is so hot that the metals in it are all in the liquid state. The outer core is composed of the melted metals of nickel and iron.

33 The Inner Core The inner core has temperatures and pressures so great that the metals are squeezed together and are not able to move about like a liquid, but are forced to vibrate in place like a solid.

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35 Convection Currents The asthenosphere "flows" because of convection currents. Convection currents are caused by the very hot material at the deepest part of the mantle rising, then cooling and sinking again --repeating this cycle over and over.

36 Convection Currents The next time you heat a liquid like soup or water in a pan you can watch the convection currents move in the liquid. When the convection currents flow in the asthenosphere they also move the crust. The crust gets a free ride with these currents, like the cork in this illustration.

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40 Granite Basalt Peridotite and Perovskite Flows

41 Layers Defined by Composition Layers Defined by Physical Properties Crust Continental Rock: Granitic Depth: 8-75 km Density: 2.7 g/cm 3 Oceanic Rock: Basaltic Depth: 7 km Density: 3.0 g/cm 3 Lithosphere Asthenosphere Depth: 100 km Crust and upper mantle Rigid Below Lithosphere Soft and plastic-like Flows Mantle Rock: Peridotite & Perovskite Depth: 2,890 km Density: 3.4 g/cm 3 Outer Core Liquid 2,260 km thick Generates Earth s magnetic field Core Iron-nickel alloy Sphere Density: 13 g/cm 3 Inner Core Solid due to immense pressure Radius: 1,220 km

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43 Label Earth s Layers Practice Quiz Based on composition

44 Label Earth s Layers Practice Quiz Based on physical properties

45 Show What You Know! 1. What is the thinnest layer of Earth? 2. What is the thickest layer of Earth? 3. What makes up the lithosphere? 4. How are the lithosphere and asthenosphere related? 5. What is the core made of? 6. Which part of the core is liquid? 7. What are the two types of crust? 8. What is each type of crust made of?

46 Have we ever seen part of the Mantle? Explain.

47 Answer the Essential Questions What are the layers of Earth? How are each of Earth s layers different in composition and physical behavior? What process causes the movement of the lithospheric plates and how does it work?