Such a geological term as fluvioglacial deposits is not familiar to everyone, and therefore it is not surprising that it causes difficulty in understanding when it occurs in text, conversation or is the main topic of discussion. It is easy to guess that these are deposits that accumulate over time in the ground under certain conditions. What are these conditions? How do such deposits differ from, say, glacial ones? Under the influence of what are they preserved or transformed into other equally interesting forms?
Occurrence conditions
It will be difficult to understand the process of formation of geological rocks, especially with the conditions for the formation of fluvioglacial deposits, without understanding the terminology. The glacier under which the whole process takes place consists of several parts:
- Glacial tongue - a narrow part on one side of the glacier, formed due to its rapid downward movement.
- Trog is a U-shaped mountain valley, often covered with moraine.
- Ice mill - recesses from the passage of melt water through them.
- The bed of the glacier is the lower part where the water flows the slowest.
First of all, fluvioglacial deposits are observed among glaciers, which, under the influence of ambient temperature, melt and form small channels so that melt water can freely descend along them. The temperature, as well as warm winds, rains, the process of insolation, the gradually heated air near the rocks, make the sides of the glacier thaw all the time. Water with all impurities penetrates into the ice through pores and cracks. There she collects all the deposits that have accumulated over time in isolation from the external environment, and enters the bed of the glacier. Along the way, it forms glacial mills and boilers. So the process of deposit formation has begun.
Formation process
However, the glacier creates not only fluvioglacial deposits. The formation conditions of these rocks are favorable for the appearance of moraines. The moving parts of the glacier, which gradually melt and create asymmetric shapes, are next to its tongue. Cobblestones accumulate here, below - pebbles, sand and eventually silt. They are many times processed by the waters, washed and deposited again. This is called fluvioglacial, that is, water-glacial deposits.
Another phenomenon that appears due to the movement of waters is eskers. As a result of the sorting of moraines, cracks begin to be filled in layers with crushed stone, sand, gravel and pebbles, which is calledsuch a powerful term. Since the cracks go along with the glacier, these layers remain 30-70 km behind it, showing which way the ice floe is moving. Ozes do not always lie in even layers, as they were formed: such a “layer cake” breaks up and crushed stone alternates with sand, pebbles and other components.
Fluvioglacial deposits, their characteristics
Since there are other deposits that are formed under the influence of the same meltwater, the fluvioglacial material can be distinguished by its unique properties:
- Layer.
- Smoothness of rubble and pebbles.
- Sorted by severity, size and nature of debris.
Thus, the moraine does not have such a clear layering, especially in the early stages of formation, fluvioglacial deposits can be easily distinguished by this feature. In addition, the moraine contains fragments of ice, sometimes whole blocks, although washed by the waters, melted. No such formations were found in the material under consideration. But there are two types: intraglacial, currently inside, and periglacial. The latter, due to external conditions, take on a different form, and therefore have their own name (ozes, kams, zands).
Fluvioglacial deposits, their features and differences from glacial deposits
Water-glacial, as they are also called, differ from glacial deposits in sorting and layering. Glacial material is primarily that madder that is formed during the movement of melt water andis loose fragments of rocks, boulders, pebbles, mixed with clay and sand. Interestingly, fluvioglacial materials are mostly formed for the Anthropogenic, the youngest Quaternary system. For such glaciers, the process is not over yet, new cracks appear and they are filled by mountain rivers carrying the above material.
Despite the fact that these are young glaciers, their formation falls at a time when the temperate zone was completely covered with ice. If the upper layer is loose, then the lower layers on such ice floes are "cemented" and highly compacted fluvioglacial materials that have survived many metamorphoses.
A special type of deposits - kama
Besides those mentioned earlier, there are other types of fluvioglacial deposits. For example, kamas have interesting features. They, unlike externally glacial species, are not formed due to the movement of the glacier, but are sediments washed over by melt water, which once stopped here. Kams often have swampy waters at their top that do not have access to the ice bed.
In appearance, the kamas resemble hills, which are located at a height of 6 to 12 meters, while scattered at these heights randomly, without revealing any order. When the ice separates from the main body of the glacier, it melts and forms these irregular hills. The last feature is easily explained: the ice floes themselves are often irregular in shape, and unevenmelting does nothing to create symmetrical figures. Kams are found in Moscow, Leningrad and Kalinin regions in Russia.
Zanders are complex formations
Favorable soil for the formation of fluvioglacial deposits can be called terminal moraines and kames surrounding them outside the glacier. Here, pebbles, crushed stone, sand and gravel are deposited in thick layers. This is the zander. They add up to entire outwash fields, as sediments penetrate here through gentle slopes. The outwash fields have a central depression, where the deposits turn into a cone-shaped funnel - melt water went there, which brought sand and gravel in its time.
Over time, outwash fields form a whole glacial series, complex in nature. It includes a transitional cone, a moraine amphitheater (elevation), a central depression, eskers and drumlins. This term was introduced by A. Penk and has another name - glacial complex. It is best seen in the example of a glacier cut along its width. There are many more new formations that can be distinguished in a separate series, but all of them are united by their nature of origin and properties.
Geology is not an easy science
Despite the fact that geology primarily studies the composition and characteristics of different types of soils, the study of glaciers plays a special role in it. In addition, fluvioglacial deposits are a significant branch of geology, which is of interest not only to researchers and scientists, but also to engineers, architects, geologists, and many others.other scientists. The study of these types of deposits can shed light on the history of the formation of the glacier, the environment of that time and life.
Fluvioglacial materials are also valuable in a building sense: stations, research laboratories and technical buildings can only be designed and built on certain areas of glaciers. An important role is played by deposits in these places. Either way, glacial deposits are a fascinating topic of study that many unfairly ignore.
