The elements in the atmosphere did not come entirely from erosion of rock and outgassing. While these processes played a significant role, the early Earth's atmosphere was formed primarily from volcanic outgassing.

Here's a breakdown:

Outgassing:

* Volcanoes were extremely active in the early Earth, releasing vast quantities of gases trapped within the Earth's interior.

* These gases included water vapor, carbon dioxide, nitrogen, sulfur dioxide, methane, and other elements.

* This early atmosphere was vastly different from the present one, being much thicker and hotter.

Erosion:

* Over time, the cooling of the Earth led to the formation of oceans, which were further enriched by water vapor released from volcanoes.

* Erosion of rocks by wind and rain also contributed some elements to the atmosphere, including dust particles and dissolved minerals.

Other Sources:

* Comets and asteroids also contributed to the Earth's atmosphere, particularly in the early stages of its formation.

* Biological activity played a crucial role in shaping the atmosphere over time. Photosynthesis by early life forms produced oxygen, which gradually built up in the atmosphere.

Summary:

While erosion and outgassing both played significant roles, the early Earth's atmosphere was primarily formed by volcanic outgassing. Other sources, such as comets, asteroids, and biological activity, also contributed to the composition and evolution of the atmosphere over time.