Fact 1: Aglacier causes mechanical weathering.

Fact 2: Pysical weathering is the mechanical breakdown of rocks.

Given the two facts above, answer the question "What do glaciers do to rocks?" with the following options: 
- form them
 - melt them
 - protect them
 - storing water
 - throw them
 - It expands
 - Water expanding
 - break them down


 

        break them down 