What is thought to have caused the ice age

It is believed that the ice age was caused by fluctuations in the amount of solar energy received by the planet in some periods of time.

Explanation:

Ice age is the name given to the period when thick layers of ice cover large areas of the Earth. These periods can last for thousands of years and dramatically change the characteristics of the planet. There have been some very significant ice ages in the history of the planet. At the end of the 19th century, much research showed that there were several ice ages, alternating with interglacial periods. The interglacial period or interglacial phase is characterized by warmer average temperatures and consequent thawing of the glaciers, while the ice ages are periods of very cold, where the temperature of the Earth is very low causing the increase of the glaciers. It is believed that the ice age was caused by fluctuations in the amount of solar energy received by the planet in some periods of time.

Ice Age Explanation. Fluctuations in the amount of insolation (incoming solar radiation) are the most likely cause of large-scale changes in Earth's climate during the Quaternary. In other words, variations in the intensity and timing of heat from the sun are the most likely cause of the glacial/interglacial cycles.