Download Spherical Earth Lesson Outline Key

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Lesson Outline for Teaching
Lesson 1: Spherical Earth
A. Describing Earth
1. Scientists see the shape of Earth in pictures taken by satellites.
2. These pictures show that Earth is not quite a perfect sphere, which has all points on
the surface at an equal distance from the center.
3. Instead, Earth looks like a slightly flattened ball, with a(n) bulge at the equator.
B. Earth Systems
1. Earth has four systems that interact with each another.
2. Earth’s outermost system is the atmosphere, which is made up of the layer of gases
surrounding the planet.
3. Earth’s hydrosphere includes all the water found on Earth’s surface, below ground,
and as a liquid in the atmosphere.
4. As water moves between the air and Earth’s surface forming raindrops or
evaporating from puddles, the atmosphere and the hydrosphere interact.
5. Earth’s entire solid body is called the geosphere.
6. All the living things on Earth form the biosphere.
C. How did Earth form?
1. Earth and the rest of our solar system formed from a large cloud of gas and dust.
of the solar system.
3. Gravity is the force that every object exerts on every other object.
a. The strength of gravity depends on the amount of mass in objects. It also
depends on the distance between objects.
b. The more mass two objects have, the stronger the force of gravity is between
c. The closer two objects are to one another, the stronger the force of gravity is
between them.
4. Objects near Earth’s surface fall to the ground because Earth’s gravity pulls objects
toward the center of the planet.
D. The Solar Nebula
1. The solar system formed from a cloud of material called a nebula.
2. Because of the force of gravity, the cloud shrank, flattened into a disk, and began to
Earth’s Structure
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
2. Gravity made the material in the cloud come together to form the Sun and the rest
Lesson Outline continued
3. The material at the center of the rotating disk became a star that we call the Sun.
4. The remaining bits of material around the star formed planets, including Earth.
E. Early Earth
1. As Earth grew, it heated up inside. Its rocks softened and began to flow.
2. Gravity pulled surface bumps toward Earth’s center. Earth began to look like a sphere.
F. The Formation of Earth’s Layers
1. Thermal heat inside Earth melted some of the materials that formed Earth.
2. These liquid materials were able to move, or flow, and form layers.
3. Earth’s layers formed because of differences in density of the materials.
a. Density is a measure of the mass of a material per unit of volume. The denser
a material is, the more mass it has per unit volume.
b. The force of gravity caused denser materials to sink toward the center of Earth.
c. The least dense materials stayed at the surface of the planet.
d. The materials that had intermediate density formed the middle layer of Earth.
Discussion Question
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
How did gravity influence the formation of the solar system and the shape and structure of
Gravity causes the formation of all the different bodies in the solar system, including the
Sun and the planets. It caused the most massive body—the Sun—to form at the center of
the solar system. Gravity causes most of the bodies in the solar system to take a spherical
shape by pulling the mass of each body uniformly toward the center of the body. Gravity
also causes satellites, such as the Moon, to orbit the planet they are closest to.
Earth’s Structure