Reply #24: It's made of Basalt [View All]

[Ediacara]

It was formed when a very large object hit the Earth 4+ billion years ago. The global magma chamber differentiated as it slowly cooled, and anorthite plagioclase crystals floated to the top, forming the rugged white highlands covering most of the Moon. Some time later, massive flood basalts erupted and created the relatively flat, black Mare that cover most of the area that faces the Earth.

Countless meteors have hit the Moon, which has created the extensive cratering on the highlands (the Mare basalts appear to have erupted after the period of intense cratering). Dust has also settled on the Moon both from space, and from meteor debris. This has caused the white anorthosite highlands to darken somewhat to a very light gray, and the black Mare basalts to lighten slightly to a very dark gray.

And so there's the Moon in 1000 words or less :-)