Scaffolded notes
Build the idea
Layers are identified by temperature trends
From the surface upward, the main layers are troposphere, stratosphere, mesosphere, and thermosphere. Scientists use changes in the direction of the temperature trend to mark boundaries. Temperature decreases through the troposphere, increases in the stratosphere, decreases in the mesosphere, and increases sharply in the thermosphere.
Weather stays low
The troposphere contains most atmospheric mass and nearly all clouds and weather. It is heated mainly from below as Earth's surface absorbs sunlight and transfers energy to the air. The stratosphere warms upward because ozone absorbs ultraviolet radiation.
Pressure and density decrease upward
Gravity pulls gas particles toward Earth, so more air is packed near the surface. As altitude increases, there are fewer particles above and around you. Air pressure and density generally decrease with altitude in every layer, even when temperature rises.
Stop and explain
Check your thinking
1. Which variable consistently decreases with altitude?
Possible response: Air pressure, and generally density.
2. Why does the stratosphere warm upward?
Possible response: Ozone absorbs ultraviolet energy.
Interactive challenge
Try the science
Arrange the layers from Earth's surface upward.
- Thermosphere
- Mesosphere
- Stratosphere
- Troposphere
Before you leave
Exit ticket
Identify the atmospheric layer where weather occurs and give one reason.