Characteristics of the Atmosphere * The atmosphere is a mixture of gases that surrounds the Earth. * It contains oxygen and protects us from the sun's ultraviolet rays. * The atmosphere has 78% Nitrogen, 21% Oxygen, and 1% of other gases. * It is held around the Earth by gravity. * As altitude increases in the atmosphere, pressure decreases. The atmosphere exerts 14.7 lbs per square inch of pressure on us at sea level due to the force of gravity on the column of air above us. We don't notice it because we're used to it.

* The layers of the atmosphere are divided by altitude, temperature, and air pressure.

The Atmosphere has four main layers: · Troposphere · Stratosphere · Mesosphere · Thermosphere

The Troposphere is the bottom layer, closest to the Earth's surface. ·It goes from sea level (0km) to 12 km (7.5 miles) up. ·The troposphere is where weather happens and where we live. ·As altitude increases, temperature decreases. ·90% of the atmosphere's mass is found in the troposphere. ·"Tropo" means turning, and the troposphere gets its name because the gases in the troposphere are always turning.

The Stratosphere is the second layer. ·It goes from 12 km (7.5 miles) to 50 km (30 miles) high. ·Temperature stays the same from 12 km to 20 km, then from 20 km to 50 km, temperature increases as altitude increases because of the ozone layer. ·The ozone layer is the upper part of the stratosphere, and is important because it absorbs UV radiation from the sun. ·"Strato" means layers, and the stratosphere gets its name because the gases in the stratosphere are in layers.

The Mesosphere is the third layer. ·It goes from 50 km (30 miles) to 80 km (50 miles) up. ·In the mesosphere, as altitude increases, temperature decreases. ·The coldest temperatures are found in the mesosphere. It can be as cold as -93 degrees Celsius. ·Not much is known about the mesosphere, but it gets its name because "meso" means middle.

The Thermosphere is the top layer. ·It goes from 80 km (50 miles) up, and doesn't really have an upper limit because it merges with space. ·As altitude increases, temperature increases. The highest temperatures are in the thermosphere, but it doesn't feel hot. This is because even though the air particles in the thermosphere are moving very fast, creating high temperatures; there are so few they don't bump into each other often, which means there is not a lot of heat. ·Radio waves bounce off the Ionosphere, in the bottom part of the thermosphere, and travel around the world. ·Auroras are colorful curtains of light seen from Earth near the poles. They are caused by charged particles from the Earth's magnetic field colliding with nitrogen and oxygen in the thermosphere.

The atmosphere is THe MoST!! Exosphere Thermosphere Mesosphere Stratosphere Troposphere Ionosphere The atmosphere is THe MoST!! THermosphere Mesosphere (ozone layer) Stratosphere Troposphere

Draw a web diagram (bubble map) for the layers of the atmosphere: Stratosphere Mesosphere Atmosphere Troposphere Thermosphere bottom layer 0-12 km (0-7.5 miles) as altitude increases, temperature decreases ionosphere and auroras found here coldest layer down to -93o C no upper limit 2nd layer up 12-50 km (7.5-30 miles) as altitude increases, temperature decreases ozone layer protects us from the sun's UV rays "meso" means "middle" third layer up 50-80 km (30-50 miles) ozone layer makes temperatures increase "strato" means "layers" 90% of atmosphere's mass is here where weather happens and where we live top layer from 80 km (50 miles) up has high temperatures, but doesn't feel hot provides oxygen and protects us from the sun's UV rays held around the Earth by gravity a mixture of gases as altitude increases, pressure decreases 78% Nitrogen, 21% Oxygen