Page 56 - Curriculum Visions Dynamic Book

Where the Moon came from
The Moon is a large space body very close to the Earth. At present the Moon and the Earth are moving apart, suggesting that they used to be much closer together.
Some people think that the Earth and the Moon formed at the same time, each building up from space debris.
Others believe that early on in the development of the Earth, when it was still liquid up to the surface, the spin was so fast that it threw off a lump, making the Moon.
But the Moon is much less dense than the Earth and so must have much less iron. That suggests the Moon and the Earth could not have come from the same body.
 These diagrams show how the Moon may have been formed.
1
Planet crashes into Earth
Another planet
Then there is the idea that the Moon may have been captured from elsewhere in the Solar System.
Most scientists now think the Moon was part of the early Earth. If this is true, then less than a billion years after the Earth had formed, it was struck a glancing blow by another planet perhaps as big as Mars.
The collision, which destroyed the other planet, produced a huge amount of debris, which then formed into a ring around the Earth. This material then began to regroup as the Moon. As this happened, the material heated up, while at the same time, new bits of rock hit the surface of the newly forming Moon from the remaining debris cloud.
Earth
2 Ring of debris formed as other planet breaks up (mainly dust)
By about 3.9 billion years ago the Moon had cooled to produce a crust, and the craters we now see
began to be preserved in the solid surface. About
three billion years ago a long sequence of volcanic activity began that filled with lavas the basins on
the side of the Moon facing the Earth.
These huge lava eruptions helped sap the heat
from the Moon, and since then it has been more or less geologically inactive.
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