1. ASCL Workshop— Boulder, CO Fundamental Concepts for Essential Principal: The Earth has a thin atmosphere that sustains life. Breakout session: 7a Recorder: Kristin Conrad Reporter: Sarah Wise

2. ASCL Workshop— Boulder, CO Fundamental Concept #1 ► The atmosphere is a mixture of solids, liquids and gases, including oxygen (21%), Nitrogen (78%), and trace gases including carbon dioxide (.02%). Some trace gases have disproportionate effects on the physical and chemical properties of the atmosphere. For example, greenhouse gases, CO2, O3, methane, and H2O vapor.

3. ASCL Workshop— Boulder, CO Fundamental Concept #2 ► ► The atmosphere has mass and is bound to Earth by gravity

4. ASCL Workshop— Boulder, CO Fundamental Concept #3 ► ► The atmosphere is thin relative to Earth’s radius.   …also relative to other planets ► ► Atmos. Has (5) layers, each comprised mainly of gases and particles. Some gases come from geological processes, some from sunlight-driven chemical reactions, and some from living things. ► ► Layers differ by composition, density and temperature, with the lowest 10km (the Troposphere) containing most weather ► ► Horizontal structure was discussed as better incorporated into the “Transport” EP

5. ASCL Workshop— Boulder, CO Fundamental Concept #4 ► Atmospheric composition is greatly affected by byproducts of life such as, oxygen produced by photosynthesis ► Life is continually shaped by, and is dependent upon, the atmosphere. For example, living things use atmospheric gases for respiration. ► The atmosphere protects living things from harmful solar rays & space debris. ► The origin of life was enabled by early atmos. Composition.

6. ASCL Workshop— Boulder, CO Concluding Remarks ► Group chose to leave discussions of variation in space and time (previous FC #4) to other EP