Describe the processes involved in the formation and evolution of Earth's atmosphere, including the role of outgassing and the Great Oxygenation Event.

Earth’s atmosphere formed through outgassing from volcanic activity, releasing gases such as water vapor, carbon dioxide, and nitrogen. The Great Oxygenation Event, approximately 2.4 billion years ago, marked a significant increase in atmospheric oxygen due to the photosynthetic activity of early cyanobacteria.