How did the end of the ice age cool the earth

In general, it is felt that ice ages are caused by a chain reaction of positive feedbacks triggered by periodic changes in the Earth's orbit around the Sun. The last ice age ended about 12,000 years ago. The next cooling cycle would be expected to start about 30,000 years or more into the future.

come closer and become far apart and become steam/gas

it is called kinetic energy