Chapter 15 Section 1 Characteristics of the Atmosphere

What is the Atmosphere???? The atmosphere is a mixture of gases that surrounds Earth. In addition to containing the oxygen you need to breathe and the atmosphere also protects us from the sun’s damaging rays. The atmosphere is always changing.

Composition of the Atmosphere The atmosphere is made up mostly of nitrogen gas. The oxygen you breathe makes up a little more than 20% of the atmosphere. The atmosphere also contains small particles such as dust, volcanic ash, sea salt, dirt and smoke. Water is also found in the atmosphere.

Atmospheric Pressure and Temperature The atmosphere is held around the Earth by gravity. Air pressure is the measure of the force with which air molecules push on a surface. Air pressure is strongest at the Earth’s surface because more air is above you. Example: Air pressure is like a human pyramid. The people at the bottom of the pyramid can feel all the weight and pressure of the people on top.

Atmospheric Pressure and Temperature Air pressure also changes as altitude increases. Some parts of the atmosphere are warmer because they contain a high percentage of gases that absorb solar energy. Other parts of the atmosphere contain less of these gases and are cooler.

Fun Atmosphere Website Atmosphere Song and Pictures

Layers of the Atmosphere Based on temperature changes, the Earth’s atmosphere is divided into 4 layers: Troposphere Stratosphere Mesosphere Thermosphere Exosphere

Layers of the Atmosphere (Think about a hamburger) Bun Mayonnaise Tomato Hamburger Bun

Layers of the Atmosphere (Think about a hamburger) Bun Exosphere Mayonnaise Thermosphere Tomato Hamburger Mesopshere Stratosphere Bun Troposphere

Troposphere Troposphere is the lowest layer of the atmosphere, in which temperature decreases at a constant rate as altitude increases. “Tropo” means turning or change—this is the layer where the gases turn and mix. Densest atmospheric layer Air pollution, weather, clouds, water vapor are all present in the troposphere.

Stratosphere Stratosphere is the layer of the atmosphere that is above the troposphere and in which temperature increases as altitude increases. Strato- means “layer” and the this is the sphere where gases are layered and do not mix well. The ozone layer that protects life on Earth by absorbing harmful ultraviolet radiation is found in this layer. Planes fly in this sphere.

Mesosphere The mesosphere is the layer of the atmosphere between the strato and thermosphere and in which temperature decreases as altitude increases. Meso means “middle” and this sphere is the middle layer. Temperatures are called in the mesosphere. This layer contains meteroids, asteroids, meteors, etc.

Layers of the Atmosphere Thermosphere This is the uppermost layer of the atmosphere, in which temperature increases as altitude increases. Thermo-means “heat” and in this sphere is where the temperatures are highest. Layers of the Atmosphere

What is the Ionosphere??? In the upper mesosphere and the lower thermosphere, nitrogen and oxygen atoms absorb harmful solar energy. As a result, the thermosphere’s temperature rises, and gas particles become electrically charged. Electrically charged particles are called ions. Therefore it is part of the ionosphere.