Unit 1 Plate Tectonics
UNIT 2: LAYERS OF THE EARTH STUDY GUIDE
The Earth is composed of four different layers. Many geologists believe that as the Earth cooled the heavier,
denser materials sank to the center and the lighter materials rose to the top.
Temperature and density increase as you move toward the center of the earth.
Therefore, the inner core has the highest pressure, density, and temperature.
KNOW AND BE ABLE TO
DRAW THIS DIAGRAM!
These four layers are…
 The crust is the outer layer of the Earth and is made of the
lightest materials (granite). The crust is cool and brittle (rocky). The
crust is the thinnest layer of the Earth. Lithosphere is a term that is
often used interchangeably with crust. All life exists on, or in, the
lithosphere.
 The mantle is much hotter and has the ability to flow. It is the
largest/thickest layer and contains most of the Earth’s mass. The
mantle is composed of very hot, dense, molten rock. Molten means
melted. The material in the mantle flows because of convection
currents.
Another name for the crust and upper mantle is the lithosphere. Below the lithosphere is the lower mantle,
or the asthenosphere, which is the part of the mantle that has the convection currents. Humans have only
dug through a part of the crust.
 The core is the densest and hottest layer of the earth. Dense means the molecules are closely packed
together.

The outer core consists of nickel and iron and is liquid.
 The inner core is also made of iron and nickel. It is liquid due to
the tremendous pressure upon it.
There are two types of crust: oceanic crust and continental crust.



The continental crust is thicker than oceanic crust but less
dense. It is made up of mostly granite.
Oceanic Crust
The oceanic crust is thinner but denser. A common rock type is
oceanic crust is basalt. Oceanic crust is denser because it
contains more iron.
Convection is the transfer of energy/ heat from one place to another by the motion of heated gas or liquid.
Convection currents occur is water, air, and magma.
Continental
Crust
Unit 1 Plate Tectonics
Magma in the earth’s mantle rises as it is heated by the earth’s core. As it nears the crust, it begins to cool
and sink. This circulation gradually moves the Earth’s tectonic plates. Think of the boiling beads- when
they were at the bottom of the beaker, they were near the heat source. They got hot and
floated upwards. As they moved away from the heat source, the cooled off and sank again.
Remember, warm things rise and cool things sink!
Mass is the amount of matter in an object. Mass is measured with a triple beam balance. The unit for mass
is grams.
Volume is the amount of space an object takes up. Volume is measured with a graduated cylinder. The unit
for volume is cubic centimeters or liters.
Density is the ratio of mass to volume. The unit for density is grams per cubic centimeter. Density is found
by dividing mass by volume. DON’T FORGET THE UNITS.
Ology- study of
Seismo- earthquake
Geo- earth
Sub- below
What should you do if something gets broken or there is an accident?
Tell a teacher
What are five things good scientists do? (Answers vary)
Safety
Scientific method steps