Earth: Our Little Blue Planet

Earth is the third planet from the sun. It is the only known planet with life. The earth is the largest of the four rocky planets (Mercury, Venus, Earth and Mars). The earth has one satellite that we call the moon. Planet Earth is also known as Terra.

The planet is geologically active. The earth’s surface creates new landforms through volcanic activity and uplifting. In addition, large bodies of water and an atmosphere support a wide variety of lifeforms.

The Surface of the Earth

Lithosphere: The lithosphere is the solid outer surface of the planet. It is about 100 kilometers thick and covered by water (71%) and land (29%). The lithosphere is  geologically active with volcanic activity and earthquakes. Although solid, this outer shell is broken into large tectonic plates. Mountain systems are created by the collision of tectonic plates.

Atmosphere: The atmosphere is the envelope of gases surrounding the planet. It is composed of nitrogen (78%), oxygen (21%), and other gases (1%). The atmosphere is very active and supports a wide range of climates. Climates range from the very cold to hot tropical climates.

Hydrosphere: The hydrosphere is the liquid and gaseous forms of water at the earth’s surface. This envelope of water is extremely active and drives much of the earth’s climate.

Life: Terra is the only planet known to support life.

Facts About the Earth

Reflections

Vocabulary

• atmosphere
• hydrosphere
• lithosphere

Notes

• Earth is the only planet in the solar system with life.
• The planet’s surface is mostly covered by water and land.
• An envelope of gases surrounds the Earth and produces many different climates that support life.

Bibliography

• About the Solar System
• NASA Science: Solar System Exploration
• A Solar System Study Guide