Lake Ice and
Snow Science
SNOW: Other Forms of Metamorphism
Gravitational metamorphism
Snow settles as it accumulates so that the depth of snow on the ground is always less than the initial amount of snowfall, especially where snow falls as large flakes and settles under the usually milder conditions near the ground. The rate of settling is directly related to snow density and depth.
Melt-freeze (MF) metamorphism
Melt-freeze metamorphism occurs when the sun melts the upper layers of the snowpack during the day, but freezing still takes place at night. With MF Metamorphism, larger grains grow at the expense of smaller ones, helping to strengthen the snowpack in most cases. With MF metamorphosis, the density of the snow pack can increase to 0.6 g cm-3.
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| Melt cluster (clustered rounded grains) |
Rounded poly-crystals | Slush (snow grains completely surrounded by liquid water) |
| All photographs by S. Colbeck | ||
| MORPHOLOGICAL CLASSIFICATION | PROCESS-ORIENTED CLASSIFICATION | ADDITIONAL INFORMATION ON PHYSICAL PROCESSES AND STRENGTH | |||||
| Basic Classification | Subclass | Shape | Place of Formation | Classification | Physical Processes | Dependence on most important parameters | Common effect on strength |
| Wet Grains | Clustered rounded grains | Clustered rounded crystals held together by large ice-to-ice bonds; water in internal veins among three crystals or two-grain boundaries | Wet Snow | Grain clusters without melt-freeze cycle | Wet snow at low water content, pendular regime; clusters form to minimize surface free energy | Meltwater can drain; too much water leads to slush; freezing leads to melt-freeze particles | Ice-to-ice bonds give strength |
| Rounded poly-crystals | Individual crystals are frozen into solid polycrystaline grain; may be seen either wet or frozen | Wet Snow | Poorly bonded; rounded single crystals | High liquid content; equilibrium form of ice in water | Water drainage blocked by impermeable layer or ground; high energy input to snow cover by solar radiation, high air temperature or water input | Little strength due to decaying bonds | |