Geologic history of the moon

The geologic history of the moon has been defined into six major Epochs, called the lunar geologic timescale. The origin of the moon was about 4.5bya (billion years ago), close to the age of planet earth, the newly formed moon was in a molten state and this resulted in orbiting much closer to the earth resulting in tidal forces.

Exploring Shorty Crater during the Apollo 17 mission to the Moon. This was the only Apollo mission to include a geologist (Harrison Schmitt). NASA photo

These tidal forces deformed the molten body into an ellipsoid (spherical or circles) with the major pointed towards to earth.

• The first and important event in the geologic history of the moon was the crystallization of the near global ocean. it is not known with certainly what its depth was, but several studies imply a depth of about 500km or greater.
The first mineral to form in this ocean were the Iron (Fe) and Magnesium (Mg), Silicates (Si04), Olivine, and pyroxene.

Because these minerals were denser than the molten material around them, they sank easily after crystallization which was just 75% complete, less denser anorthositic plagioclase feldspar crystallized and floated, forming an anorthositic crust about 50km in thickness. Read more?

• Most of the magma ocean crystalized very quickly (within/about 100million years or less) while the final remaining KREEP-rich magmas, which are highly enriched, which are heat producing elements.

KREEP: it is an acronym built from the letters K (the atomic symbol for potassium), REE (rare-earth elements) and P (for phosphorus), is a geochemical component of some lunar impact breccia and basaltic rocks. Its most significant feature is somewhat enhanced concentration of a majority of so-called "incompatible" elements readmore

Finally theKREEP-rich magmas of the magma ocean became concentrated within the region of the "Oceanus Procellanium".

My Previous Articles on the moon

Reference: Wikipedia visit
Oxford Geology and earth science dictionary