Terrae2.3 - Be able to recognise the appearance of the principal naked-eye lunar surface formations (continued in 2.4)
2.4 - Understand the structure and origin of the principal naked-eye lunar surface formations, including:
c - terrae
Terrae appea rlighter than marian the as they contain less iron-rich elements. There is more terrae on the far side of the moon.
Rocks brought back from the Apollo missions have shown they were formed 3-4 billion years ago.
There was a period called the ‘Heavy Bombardment’ when the Moon (and presumably the inner Solar System) underwent a time of frequent and violent impacts.
Millions of years (sometimes as many as 500 million years) later the Moon underwent a time of volcanic activity and lava was forced to the surface. This lava later turned to basalt. It flooded the lower impact areas and would have covered any other features on the landscape including other craters. The highlands were left untouched.
Today we can see a large number of craters on the Terrae and fewer on Maria which also implies they were formed at different times.