Name:
Objective: I can compare and contrast Earth’s
physical layers.
Date:
Homeroom:
Handout #: 1.2
Objective: I can
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DO NOW
Answer in complete sentences where appropriate.
1. What are Earth’s chemical layers in order from hottest to coolest?
1. Draw a picture of Earth’s chemical layers.
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2. Explain in two complete sentences how the crust and mantle differ.
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Objective: I can compare and contrast the lithosphere, asthenosphere, and mesosphere.
The Physical Structure of the Earth
Another way to look at the Earth is to examine the physical properties of its layers. The
Earth is divided into five physical layers—the lithosphere, asthenosphere, mesosphere, inner
core, and outer core. As shown below, each layer has its own set of physical properties.
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1. What is the difference between categorizing Earth’s layers by chemical composition and
physical properties?
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2. What are the five physical layers of Earth?
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Lithosphere
Tectonic Plates
Pieces of the lithosphere that move around on top of the plasticlike asthenosphere are
Shoulder partners: Look at the picture below. How does the size of the plates compare to
the size of continents? Also, what do tectonic plates remind you of? What else do you
notice about the plates?
called tectonic plates. But what exactly does a tectonic plate look like? How big are
tectonic plates? How and why do they move around?
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3. Name an example of a plate that has only oceanic crust.
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4. Name an example of a plate that has oceanic and continental crust.
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Composition of Earth’s Plates
Tectonic plates are made of the crust and upper mantle. These two parts combined are the
lithosphere. This rigid layer is about 100 km thick and generally is less dense than material
underneath. The plasticlike layer below the lithosphere is called the asthenosphere. The
rigid plates of the lithosphere float and move around on the asthenosphere.
The figure below shows what the South American plate might look like if it could be lifted
out of its place. Notice that is consists of both oceanic and continental crust. The thickest
part is the continental crust. The thinnest part is in the mid-Atlantic ocean.
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5. What are tectonic plates?
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6. What does the lithosphere include?
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7. What physical layer lies just beneath the lithosphere?
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The Mesosphere
The mesosphere is the part of the mantle that lies beneath the lithosphere and
asthenosphere, but above the outer core. The upper boundary is defined as the sharp
increase in seismic wave velocities and density at a depth of 660 km. As depth increases,
pressure builds and forces material into a denser, more rigid1 structure. Therefore, the
difference between mesosphere and asthenosphere is likely due to density and rigidity
differences, that is, physical factors, and not to any difference in chemical composition. The
base of the lower mantle is at about 2700 km.
8. What does it mean that the asthenosphere and mesosphere are physically different but
not chemically different?
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Rigid means not easily moved.
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9. Does density increase or decrease in Earth’s layers as pressure increases? Why?
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Instructions: Fill in the table below with important information about each of Earth’s
physical layers.
Lithosphere
Asthenosphere
Mesosphere
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