Glacier ice has great erosive power removing ... They get cut off so while erosion makes the main valley deeper and deeper, the smaller valley is left hanging higher up above the valley floor.
Erosion transports the fragments away ... Back up on the mountains, snow and ice build up into glaciers that weigh on the rocks beneath and slowly push them downhill under the force of gravity.
Modeling glacier behavior involves firstly the physical parameters of ice flow, then topographical parameters, and finally meteorological parameters that can go far back into the past.
Opinions expressed by Forbes Contributors are their own. David Bressan is a geologist who covers curiosities about Earth. Research has shown the complex history behind this gap of missing time ...