Download 2.4 - Layers of the Earth I

SCIENCE
Grade
________/_________
2.4 (LAYERS OF THE EARTH I) • DYNAMIC EARTH
Name:
Date:
Cohort:
CATALYST
1.)
2.)
3.)
OBJECTIVE
SWBAT create a poster presentation outlining the physical characteristics of an interior layer of the Earth
Criteria For Success (CFS)
Students will submit a 2-3 slide PowerPoint containing all of the requisite information
(composition, density, relative density, approximate depth, and special characteristics)
Regents Earth Science
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2.4 (LAYERS OF THE EARTH I) • DYNAMIC EARTH
If a doctor needs to see inside your body without cutting you open, he or she can use such tools as
X-rays and CAT scans. However, these techniques are not able to penetrate thousands of
kilometers of solid rock. Scientists have found another way to examine Earth. Earthquake waves
do travel through Earth’s interior, and they can be used to obtain information about its structure.
From observing which earthquake waves travel through the planet, where they are detected, and
the speed at which they travel, scientists make inferences about Earth’s structure. Based on direct
observations and analysis of seismic waves, scientists have divided the solid planet into four layers:
crust, mantle, outer core, and inner core, as shown in the Earth Science Reference Tables.
PowerPoint/Poster Structure:
1st Slide: Title & Names of all participants (first and last names)
2nd – 3rd Slide: Physical characteristics of your layer
 What is the layer called?
 What is its density?
o Is it more or less dense than the other layers?
 What is it made of?
 What phase of matter is it in?
 What is the depth of the layer? What layers (if any) are above and below it?
 What evidence do you have of these properties? In other words, how did scientists figure
discover information about this Earth layer?
 What other information is important to know?
Poster Structure:
 Names of all participants (write on back of poster)
 What is the layer called?
 What is its density?
o Is it more or less dense than the other layers?
 What is it made of?
 What phase of matter is it in?
 What is the depth of the layer? What layers (if any) are above and below it?
 What evidence do you have of these properties? In other words, how did scientists figure
discover information about this Earth layer?
 What other information is important to know?
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2.4 (LAYERS OF THE EARTH I) • DYNAMIC EARTH
The Crust:
The crust is the outermost layer of Earth. In all of the mining and drilling humans have done, this is the only
layer that has been observed directly. In most places a thin layer of sedimentary rocks covers metamorphic and
igneous rocks. The deeper you dig, the greater the chance of finding igneous rocks. Within the continental
crust, the overall composition is close to the composition of granite. Under the sediments and sedimentary
rocks of the oceans, the crust is more dense. This is verified by observing that most volcanoes that erupt
in the ocean basins bring lava to the surface that hardens to form basalt. Geologists therefore infer that the crust
under the oceans is mostly basalt or has a similar composition. Furthermore, from very deep mines, scientists
know that the temperature within the crust increases with depth at a rate of about 1°C per 100 m. Based on this
rapid rate of temperature change, it seems logical that Earth’s interior is very hot.
The bottom of the crust is inferred from observations of earthquake waves. Seismic waves that travel through
just the crust are slower than are those that dip below the crust and enter the mantle (because the mantle has a
different composition, the waves travel at a different velocity). This change in seismic wave speed occurs at
depths as shallow as 5 km under the oceans to as deep as 60 km under some mountain ranges on land. The
Croatian geophysicist Andrija Mohorovicic first noticed this boundary, and it is now named in his honor.
However, most people shorten the name of the boundary to the Moho.
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2.4 (LAYERS OF THE EARTH I) • DYNAMIC EARTH
The Mantle:
The mantle extends from the bottom of the crust to a depth of about 2900 km. In fact, it contains
more than half of Earth’s volume. However, the inability to penetrate below the crust with mines
or drills means that investigations of the mantle must be conducted by other means.
From studies of volcanic eruptions, scientists believe that magma that originates below the crust is
rich in dense, mafic minerals such as olivine and pyroxene. These are the minerals on the right side
of the Scheme for Igneous Rock Identification in the Earth Science Reference Tables. Some
magma originates in the crust beneath mountain areas where Earth’s crust is thick and felsic in
composition.
Most of the meteorites that fall to Earth are composed of dense, mafic minerals such as pyroxene
and olivine. These are called stony meteorites. Scientists believe that these meteorites are the
material from which Earth and the other planets formed billions of years ago, or they are the
remains of a planet that was torn apart by a collision with another object. If this is the case, you
would expect meteorites to have a composition similar to the planets, including Earth.
The diameter of planet Earth has been known for centuries. From this value, it is easy to calculate
Earth’s volume. The mass of Earth has been determined based on its gravitational attraction.
Knowing Earth’s mass and volume, scientists have calculated that Earth’s overall density is about
5.5 g/cm3. That is about twice as dense as most rocks in the crust. Therefore, scientists expect the
mantle, which includes most of Earth’s volume, to be composed of minerals that are more dense
than those in the crust are.
Earthquake waves can travel through the mantle. Because some type of earthquake waves will not
travel through a liquid, the mantle is known to be in the solid state. Furthermore, earthquake
waves travel faster in the mantle than they do in Earth’s crust. This indicates that the rock in the
mantle is more brittle than crustal rocks. Again, olivine and pyroxene fit the observations. All
these observations provide strong evidence that Earth’s mantle is composed primarily of iron- and
magnesium-rich, mafic silicate minerals. Therefore, geologists infer that the mantle is composed
mostly of olivine and pyroxene in the solid state.
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2.4 (LAYERS OF THE EARTH I) • DYNAMIC EARTH
The Core:
Starting at 2900 km and extending to Earth’s center is the next layer, called the core. Seismologists
noticed that some types of earthquake waves can penetrate the whole planet, but other types do
not travel through Earth’s core. Scientists also know that these waves, called P-waves, cannot
travel through liquids. Since they know that P-waves cannot travel through the core, they think
that the core must be liquid.
Starting from the atmosphere, each of Earth’s layers is more dense than the layer above it:
atmosphere, hydrosphere, crust, mantle. You might therefore expect the core to be even more
dense than the mantle. Scientists also know about the core and its high density from studying
meteorites, or small to medium-sized rocks that have fallen from space. One particular type of
meteorite is mostly composed of iron. From studying this type of meteorite, scientists also think
that they core of the Earth also contains mostly iron, with some nickel as well. Scientists have also
inferred that the outer core is liquid because the movement of liquid iron in the outer core is also
thought to cause Earth’s magnetic field.
Scientists think that the extreme pressure generated by the weight of the Earth above makes the
liquid core a solid at the very center of the Earth. Geologists have inferred this based on the way
those abovementioned earthquake waves travel. Because the waves change their speed and
direction (refract) when they travel through solids or liquids, scientists have noticed that
earthquakes waves often refract when they travel through the center of the Earth. Thus, they have
also concluded that there is a solid inner core surrounded by a liquid outer core.
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2.4 (LAYERS OF THE EARTH I) • DYNAMIC EARTH
Practice/HW: Using the information above and “Inferred Properties of Earth’s Interior” on page
10 of the ESRT, complete the following questions.
Crust Facts:
1. The two types of crust are ____________________and ____________________.
2. The density of the oceanic crust is ____________________ g/cm3 and made up of the igneous
rock ____________________. The density of the continental crust is ____________________
g/cm3 and is made of the igneous rock ____________________.
3. The thickness of the crust is ____________________ km.
4. The temperature of the crust ranges from ____________________ C to
____________________ C.
5. The crust-mantle boundary is called the ____________________.
6. The crust and the rigid upper part of the mantle is called the ____________________.
Mantle Facts:
1. The uppermost part of the mantle that has plastic properties is the ____________________.
2. The density of the mantle ranges from ____________________ g/cm3 to
____________________ g/cm3.
3. The thickness of the mantle is ____________________ km.
4. The actual temperature of the mantle at the 2,000 km depth is ____________________C
5. As depth increases, pressure in the mantle ____________________.
Outer Core Facts:
1. The outer core is inferred to be made up of what element? ____________________
2. The thickness of the outer core is ____________________ km.
3. The actual temperature of the outer core is between 5,000 C and 6,200 C. The melting point
of iron is (GREATER or LESS) than the actual temperature. This means that the outer core is
made up of (SOLID or LIQUID) iron.
4. The pressure of the outer core is between ____________________ and
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2.4 (LAYERS OF THE EARTH I) • DYNAMIC EARTH
____________________ millions of atmospheres.
5. The density of the outer core ranges from ____________________ g/cm3 to
____________________ g/cm3.
Inner Core Facts:
1. The thickness of the inner core is ____________________ km.
2. The actual temperature of the inner core ranges from ____________________ C to
____________________ C.
3. The inner core is made up of ____________________ and ____________________.
4. The melting point of iron is (GREATER or LESS) than the actual temperature of the inner
core. Therefore, the rock in the inner core is (SOLID or LIQUID).
5. The density of the inner core ranges from ____________________ g/cm3 to
____________________ g/cm3.
6. The pressure at the center of the earth is ____________________ millions of atm.
Conclusion:
As the distance from the surface increases, write what happens to the (1) temperature, (2) pressure,
and (3) density below:
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