Which of the following BEST describes the dynamics of a typical alpine glacier:

W) the relative position of particles within the ice remains stationary

X) retreating glaciers carve out V-shaped valleys

Y) high pressures created by the mass movement of ice can produce meltwater deep within a glacier

Z) they move downhill primarily under the influence of ice avalanching
\[\text{ Y) HIGH PRESSURES CREATED BY THE MASS MOVEMENT OF ICE CAN PRODUCE MELTWATER DEEP WITHIN A GLACIER