Subsurface Ice

Subsurface Ice

 

ice in the earth’s crust of any origin or mode of occurrence. In terms of time of formation, a distinction is made between modern and fossil ice, and in terms of origin, primary (syngenetic), secondary (epigenetic), and buried ice are distinguished.

Primary subsurface ice is formed during the freezing of accumulating deposits that are loose before freezing. It constitutes a predominant part of subsurface ice and is found primarily in the form of contact, interstitial, and film basal ice cement and, more rarely, in the form of large lenses and bands, known as segregation or injection ice. The formation of the last two types of subsurface ice causes frost heaving on the earth’s surface.

Secondary subsurface ice is the product of the crystallization of water and water vapor in cracks (vein ice) and pores and cavities (honeycomb ice) of solidly frozen rock or already formed rock that is freezing. As a result of the annually recurring filling of frost cracks with ice, reveined ice is formed, occurring in the form of a tetragonal lattice of stratified vertical ice veins. If new sediments accumulate at the same time as ice veins form, the ice veins will gradually grow as the level rises. Such (syngenetic) ice veins grow during the accumulation of freezing sediments to a width of up to 8 m and a height of up to 40–80 m, constituting up to 70 percent of the area of the coastal plains of northern Siberia and Alaska.

Epigenetic recurring ice veins that penetrate frozen loose sediments do not extend to a depth of more than several meters.

Buried ice is formed initially on the earth surface (for example, snowfields, icing, and sea, lake, and river ice) and is later buried beneath sedimentary rock. The largest masses of buried ice are the “dead ice” of glaciers. All buried ice taken together constitutes the smallest portion of subsurface ice.

REFERENCES

Shumskii, P. A. Osnovy strukturnogo ledovedeniia. Moscow, 1955.
Osnovy geokriologii (merzlotovedeniia), part 1. Moscow, 1959.
Dostovalov, B. N., and V. A. Kudriavtsev. Obshchee merzlotovedenie. Moscow, 1967.
References in periodicals archive ?
The crater could be younger, or perhaps the impact that created it hit a pocket of ammonia-rich subsurface ice.
Shifting pockets of subsurface ice could put more spring into the overlying terrain, eroding the oldest craters.
Last month as Dawn neared Ceres, it relayed images of startlingly bright spots on the surface, which could be patches of subsurface ice exposed after an asteroid or comet impact.
While recent orbiter missions have confirmed the presence of subsurface ice, and melting ground-ice is believed to have formed some geomorphologic features on Mars, this study used meteorites of different ages to show that significant ground water-ice may have existed relatively intact over time.
Researchers at the American Geophysical Union meeting Tuesday in San Francisco discussed a range of current Martian activity, from fresh craters offering glimpses of subsurface ice to multi-year patterns in the occurrence of large, regional dust storms.
The craters are found primarily at higher latitudes, a location that correlates with thick, fine-grained sedimentary deposits rich with subsurface ice.
They say it is a thick layer of subsurface ice, amounting to several thousand tonnes of water.
Mars is a cold, dry place, although the arctic region under study is believed to hold vast quantities of subsurface ice.
Another theory is that subsurface ice is rapidly heated, vapourising in an explosion.
Two oceans have been proposed: 4 billion years ago, when warmer conditions prevailed, and also 3 billion years ago when subsurface ice melted, possibly as a result of enhanced geothermal activity, creating outflow channels that drained the water into areas of low elevation.
It's possible, she says, that subsurface ice in the area formed patterns and then sublimated long ago.
Two oceans have been proposed: 4 billion years ago, when warmer conditions prevailed, and also 3 billion years ago when subsurface ice melted following a large impact, creating outflow channels that drained the water into areas of low elevation.