When the ice age ended, the glaciers slowly retreated until they reached their current extent limited to the polar regions and alpine mountain climates. The land covered by ice had also been depressed by the weight of the massive glaciers and consequently began to rebound in the centuries following the retreat of the ice sheets. These once frozen lands also turned into large boreal forests with rich ecosystems.
To help put together pieces of information together the physical geographers must borrow from other disciplines and they make use of the tools that are available to them in the forms of the maps and aerial surveys and interaction of the biological system as the ecosystem and the hydrological system along with the climatology system that helps them define the physical characteristics if the place and regions on globe.
Primary producers are organisms that make their own food, such as plants. They do this through photosynthesis, which requires sunlight, water, and carbon dioxide.
