Questions and Answers about: Planet Earth

Introduction

Earth is the only planet in the universe known to harbor life. It is surrounded by a protective blanket of air—the atmosphere—that allows us to breathe and prevents the planet from becoming too hot. The Earth’s orbit around the Sun, and its tilted axis, are responsible for its weather, its climates and its seasons. The planet’s often dramatic landforms—its mountains, valleys and caves—were formed over millions of years by erosion and the movement of the Earth’s crust.

In this book, you can learn all about our home planet, its landscapes and oceans, and the violent natural disasters that frequently rage across its surface. Along the way, you will discover many fascinating facts. Why are days longer in summer and shorter in winter? How do volcanoes create caves? What was the worst earthquake in history? You will find the answers to these and many other questions in the pages of this book.

Earth’s Atmosphere

The protective blanket of air that covers the Earth is called the atmosphere. The Earth’s atmosphere not only prevents too much heat from entering the planet, but also protects us from asteroids and meteors. The Earth’s gravity helps hold the atmosphere in place.

Quick Q’s:

1. What is a barometer?

A barometer is used to measure the pressure in the atmosphere. When the pressure is high, the weather will be fine, sunny and still. When it is low, the weather will be stormy. When the pressure increases the liquid in the barometer is squeezed and when the pressure decreases it is released. This change is recorded.

2. What is the exosphere?

The exosphere is the final layer of the Earth’s atmosphere. It extends way into outer space. The air in the exosphere is very thin, but the temperature is very high, because the Sun’s rays shine directly on it.

3. Why is the ozone layer important?

The ozone layer is important because it stops harmful ultraviolet rays from the Sun from reaching the Earth. If the rays are allowed through the atmosphere, they can cause severe health problems like skin cancer. Chemicals called CFCs have made a hole in the ozone layer above the North and South Poles.

Q How many layers does the Earth’s atmosphere have?

A The Earth’s atmosphere is composed of several layers. These include the troposphere and the stratosphere. Each layer is divided according to the temperature and density of air in that layer.

bull Long way out

The outer layers of the atmosphere extend far into space.

Q What are the gases that make up the Earth’s atmosphere?

A The Earth’s atmosphere is composed of many gases. Nitrogen is the main gas found in the atmosphere. It accounts for about 78 percent and oxygen makes up 21 percent. The remaining one percent is a combination of carbon dioxide and water vapor. There are also very small amounts of trace gases like neon and helium that go to make up the Earth’s atmosphere.

bull A warm blanket

The Earth is protected by layers of gases. SOHO sends information about these layers back to Earth.

Q What is the significance of the troposphere in the weather pattern?

A The troposphere is the layer