During these periods, snow and ice accumulated in the high mountain valleys eventually creating a moving wall of ice in the form of a glacier, which flowed downhill and carved spectacular U-shaped valleys and pushed debris and eroded rock in front of it like a bulldozer.
(snow and ice; accumulated; L:in the high mountain valleys) (a glacier; pushed; debris) (the high mountain valleys; creating; a moving wall of ice in the form of a glacier; T:During these periods; T:eventually) (a glacier; flowed; downhill) (a glacier; carved; spectacular U-shaped valleys)
snow and ice a glacier the high mountain valleys a glacier a glacier
accumulated pushed creating flowed carved
L:in the high mountain valleys
debris
a moving wall of ice in the form of a glacier T:During these periods T:eventually
downhill
spectacular U-shaped valleys