Formation
When the water surface begins to lose heat rapidly, the water becomes supercooled. Turbulence, caused by strong winds or flow from a river, will mix the supercooled water throughout its entire depth. The supercooled water will already be encouraging the formation of small ice crystals (frazil ice) and the crystals get taken to the bottom of the water body. Ice generally floats, but due to frazil ice's ineffective buoyancy, it can be carried to the bottom very easily.
Through a process called secondary nucleation, the crystals quickly increase in number, and because of its supercooled surrounding, the crystals will continue to grow. Sometimes, the concentration is estimated to reach one million ice crystals per cubic meter.
As the crystals grow in number and size, the frazil ice will begin to adhere to objects in the water, especially if the objects themselves are at a temperature below water’s freezing point. The accumulation of frazil ice often causes flooding or damage to objects such as trash racks. Since frazil ice is found below the surface of water, it is difficult to detect its formation.
Usually what happens is the frazil ice accumulates on the upstream side of objects and sticks to them. The frazil ice accumulates as more gets deposited. The growth will extend upstream and increase in width until the point where the frazil ice accumulations bridge together and block the water. As more and more water flows against this block, the pressure on the upstream side increases and causes a differential pressure (difference in pressure from the upstream side and the downstream side). This will cause the growth of the bridge to extend downstream. Once this happens, flooding and damage is likely unless otherwise prevented.
Frazil ice has also been demonstrated to form beneath temperate (or "warm-based") glaciers as water flows quickly uphill and supercools due to a rapid loss of pressure. This "glaciohydraulic supercooling" process forms an open network of platy ice crystals that can effectively trap silt from the sediment-laden water that flows beneath glaciers and ice sheets. Subsequent freezing and recrystallization can result in a layer of sediment-rich ice at the base of the glacier which, upon melting at the terminus, can result in significant accumulation of sediment in moraines. This phenomenon has been verified by elevated concentrations of bomb-produced tritium in the basal ice of several glaciers (signifying young ice) and the observation of rapid growth of ice crystals around water discharge vents at glacier termini.
Read more about this topic: Frazil Ice
Famous quotes containing the word formation:
“The formation of an oppositional world view is necessary for feminist struggle. This means that the world we have most intimately known, the world in which we feel “safe” ... must be radically changed. Perhaps it is the knowledge that everyone must change, not just those we label enemies or oppressors, that has so far served to check our revolutionary impulses.”
—Bell (c. 1955)
“... the mass migrations now habitual in our nation are disastrous to the family and to the formation of individual character. It is impossible to create a stable society if something like a third of our people are constantly moving about. We cannot grow fine human beings, any more than we can grow fine trees, if they are constantly torn up by the roots and transplanted ...”
—Agnes E. Meyer (1887–1970)
“Out of my discomforts, which were small enough, grew one thing for which I have all my life been grateful—the formation of fixed habits of work.”
—Elizabeth Stuart Phelps (1844–1911)