We are going to use models and activities to demonstrate how the active environment of a solar system shapes and changes the surface of planets both suddenly, and gradually over long periods of time. ...We are going to use models and activities to demonstrate how the active environment of a solar system shapes and changes the surface of planets both suddenly, and gradually over long periods of time. The theory that things usually change gradually over time, but occasionally are radically transformed by titanic events is called punctuated equilibrium. There is a lot to learn about how the surface of the Earth and Moon got the way they are today, so let’s go exploring!