How do geologists determine where glaciers may have been in the past? what tools are required? what pieces of evidence are crucial to determine something like the existence of snowball earth?

There exists continental ans valley glaciers who ages have determined on the basis of rock types and carbon datings

Explanation:

Glaciers were formed some 34 million years ago, in which first small glaciers were seen in Antarctica and that was 20 million years ago as the glaciers froze on to rocks and southern ice sheets were formed. The snowball earth existed from 2.4 to 2.1 billion years ago, at that time Huronian glaciation i.e oldest ice age was built on earth having unicellular mass. As in the earlier phase, the snowball was completely frozen and 250 million years after the big volcanic activity that spread the carbon dioxide into the atmosphere and created the greenhouse gases. Evidence can be taken from the quaternary period of glaciation some 2.58 million years ago. As the ice sheets have gone through the multiple periods of growth and retreat as in the interglacial period the ice melted and retreated. Roughly about 41,000 million years ago the tilting of axis of the earth had a major effect on the ice sheets around the globe.

He got it right defiantly right