Download Earth`s Inner Layers

Earth’s Inner Layers
Dana Desonie, Ph.D.
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Printed: September 15, 2014
AUTHOR
Dana Desonie, Ph.D.
www.ck12.org
C HAPTER
Chapter 1. Earth’s Inner Layers
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Earth’s Inner Layers
• Identify Earth’s internal layers.
• Describe the characteristics of Earth’s layers.
• Distinguish the lithosphere and from the asthenosphere.
What’s below our feet? What’s way below?
If we could cut Earth open, we’d see the following layers from inside to outside: inner core, outer core, mantle, and
crust. Alternatively, you can think of the brittle lithosphere riding on the plastic asthenosphere. Whew!
Layers by Composition
The layers scientists recognize are pictured below ( Figure 1.1).
Core, mantle, and crust are divisions based on composition:
1. The crust is less than 1% of Earth by mass. The two types are oceanic crust and continental crust.
2. The mantle is hot, dense, dark (ultramafic) rock. It represents about 68% of Earth’s mass.
3. The core is mostly iron metal. The core makes up about 31% of the Earth. Earth’s metallic core has two
layers: a solid inner layer and a liquid outer layer.
The terms core, mantle, and crust will be described in more detail in the next three concepts.
Layers by Mechanical Properties
Lithosphere and asthenosphere are divisions based on mechanical properties:
1. The lithosphere is composed of both the crust and the uppermost mantle. The lithosphere is a brittle, rigid
solid. It is easily cracked or broken.
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FIGURE 1.1
A cross section of Earth showing the following layers: (1) crust (2) mantle (3a)
outer core (3b) inner core (4) lithosphere
(5) asthenosphere (6) outer core (7) inner
core.
2. The asthenosphere is below the lithosphere. The asthenosphere is also in the upper mantle. This layer is
solid, but it can flow and bend. A solid that can flow is like silly putty.
This animation shows the layers by composition and by mechanical properties: http://earthguide.ucsd.edu/eoc/teach
ers/t_tectonics/p_layers.html .
Vocabulary
• asthenosphere: Layer below the lithosphere, made of a portion of the upper mantle; the asthenosphere can
flow.
• core: Innermost, densest layer of a celestial body.
• crust: Rocky outer layer of the Earth’s surface.
• lithosphere: Layer of solid, brittle rock that makes up the Earth’s surface.
• mantle: Middle layer of the Earth; made of hot rock.
Summary
•
•
•
•
By composition, Earth is divided into core, mantle, and crust.
By mechanical properties, the crust and upper mantle are divided into lithosphere and asthenosphere.
The core-mantle-crust divisions are based on composition.
The lithosphere-asthensophere divisions are based on mechanical properties.
Explore More
Use the resource below to answer the questions that follow.
• NASA SCI Files - Layers of the Earth at http://www.youtube.com/watch?v=227okXKJpXA (3:51)
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Chapter 1. Earth’s Inner Layers
MEDIA
Click image to the left for use the URL below.
URL: http://www.ck12.org/flx/render/embeddedobject/58890
1.
2.
3.
4.
5.
What is the core?
Explain the core’s structure.
What is the mantle?
What is the crust?
Why does the Earth have layers?
Review
1. What are the the layers of Earth, based on composition? Where are they located?
2. What is the composition of the different layers?
3. How do the lithosphere and asthenosphere differ from each other?
References
1. Courtesy of the US Geological Survey. Composition of Earth’s layers. Public Domain
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