What factors contributed to the formation of a very thick ice sheet in Antarctica and huge deserts in Africa?

Antarctica is the coldest continent. The ice cover is constantly replenished due to snow falling and frost formation on the ice surface. In summer, ice melts on the outskirts at temperatures above 0, but the land still does not free itself from the ice cover, since there is a constant flow of ice from the center.
There are many huge deserts in Africa, since it is located in low latitudes and is characterized by high temperatures and dry air. There are irregular rains, in some areas every few years.