The moon spent a few million years as a volcanic wasteland, covered with ongoing eruptions that spewed from mountains and even from the ground itself.

Our moon may have once been as hellish as Jupiter's super volcanic moon Io

Source: space
Source Link: https://www.space.com/astronomy/moon/the-moon-may-have-once-resembled-jupiters-io-the-most-volcanic-body-in-the-solar-system