Earth's Changing Atmosphere Through Time

A Journey Through 4.6 Billion Years Year 9 Science WALT: We Are Learning To understand how Earth's atmosphere has evolved

What is Earth's Atmosphere Today?

78% Nitrogen (N₂) 21% Oxygen (O₂) 0.04% Carbon Dioxide (CO₂) Trace amounts of other gases This composition supports complex life

Timeline: Earth's Atmospheric Evolution

Stage 1: Early Earth's Volcanic Atmosphere

4.6 to 4.0 billion years ago Atmosphere from volcanic outgassing Mainly water vapor, carbon dioxide, methane No oxygen - would be toxic to most life today Very hot greenhouse effect

Practical Investigation: Oxygen and Candles

Work in groups of 4-5 Light candles in different jars Jar A: Candle only Jar B: Candle with fresh leaves Measure how long candles burn Record observations and discuss results

Stage 2: The Great Oxidation Event

2.4 billion years ago Cyanobacteria evolved photosynthesis Oxygen began accumulating in atmosphere Toxic to many early life forms Led to mass extinction of anaerobic organisms

Human Impact on Modern Atmosphere

{"left":"Burning fossil fuels increases CO₂\nDeforestation reduces oxygen production\nIndustrial processes release greenhouse gases","right":"Concentration of CO₂ has risen 40% since 1850\nEnhanced greenhouse effect causes climate change\nRising global temperatures affect weather patterns"}

Reflection and Next Steps

How do living organisms affect the atmosphere? How do atmospheric changes affect living organisms? What can we do to protect our atmosphere? Success Criteria Check: Can you explain the key stages of atmospheric evolution?