Why do Ice Ages Occur?

Scientists have several ideas and theories on the causes of ice ages. One of the earliest ideas about the causes of ice ages was made in 1920 that glaciations could be caused by the Earth’s position relative to the Sun. Two other known factors which play a part in the presence of ice ages are plate tectonics and the position of plates in the polar regions as well as changes in global sea level.

There are also some theories which are not fully supported with evidence, or which do not have the approval of most scientists. A few of these theories are:

That heat output from the Sun varies with time and can therefore cause ice ages.

That there exists interplanetary dust which can restrict sunlight from reaching the Earth.

Also that meteorite impacts can cause ice ages.