When geographers observe moraines, they can conclude that

Something must have been moving along and either plowed the stuff to one side or carried it and deposited it along the side. What else but a glacier?  

PS. I'd guess this is more the province of geologists, not geographers

if he does not use open the compass the a width greater than half of po, he will not be able to find the midpoint of the line, without the midpoint of the line, he will not be able to bisect the line.   to find the midpoint of a line the circles drawn with a compass must either intersect or be touching.