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 a text, conversation or is the main topic of discussion. It is easy to guess that these are deposits that accumulate over time in the earth under certain conditions. What are these conditions? What is the difference between such deposits from, say, glacial? Under the influence of what do they persist or pass into other, no less interesting forms?
Conditions of occurrence
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 is a narrow part on one side of the glacier, formed due to its rapid movement down.
- Trog - a mountain valley in the form of "U", often covered with moraine.
- Glacial mill - recesses from the passage of melt water through them.
- The glacier bed is the lower part, where water flows most slowly.
First of all, fluvioglacial deposits are observed among glaciers, which thaw under the influence of ambient temperature and form small channels so that meltwater can freely descend down them. Temperature, as well as warm winds, rains, the process of insolation, gradually heated air near the rocks, make the sides of the glacier melt all the time. Water with all impurities penetrates into the ice in pores and cracks. There she collects all the deposits that have accumulated over time in isolation from the external environment, and falls into the glacier bed. Along the way, it forms glacial mills and boilers. So, the deposition process has begun.
Formation process
However, the glacier creates not only fluvioglacial deposits. The conditions for the formation of these rocks are favorable for the appearance of moraines. Moving parts of the glacier, which gradually melt and create asymmetric figures, are located next to its tongue. Cobblestones accumulate here, below - pebbles, sand and ultimately silt. They are processed many times by water, washed and shelved again. This is called fluvioglacial, that is, water-glacial deposits.
Another phenomenon that appears due to the movement of water is ozy. Cracks as a result of sorting moraines begin to fill with layers of rubble, sand, gravel and gravel, which is called such a capacious term. Since cracks go along with the glacier, these layers remain 30–70 km behind it, indicating which direction the ice floe is moving. Ozi do not always lie in even layers, as they formed: such a “layered 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, fluvioglacial material can be distinguished by its peculiar properties characteristic of it alone:
- Layering.
- The smoothness of rubble and pebbles.
- Sorted by severity, size and nature of the debris.
So, the moraine does not have such a clear layering, especially in the early stages of formation, fluvioglacial deposits can be distinguished by this attribute without difficulty. In addition, the moraine has in its composition fragments of ice, sometimes whole blocks, although washed with water, melted. No such formations were found in the material under consideration. But there are two types: intraglacial, which are currently inside, and glacial. The latter, due to external conditions, take a different form, and therefore have their own name (oz, kama, zanda).
Fluvioglacial deposits, their features and differences from glacial
Water-glacial, as they are also called, differ from glacial deposits by sorting and stratification. Glacial material is, first of all, that madder, which is formed during the movement of melt water and is loose fragments of rocks, blocks, 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 yet complete, new cracks appear and they are filled with mountain rivers carrying the above material.
Despite the fact that these are young glaciers, their formation dates back to the 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 surviving many metamorphoses, “cemented” and highly densified fluvioglacial materials.
A special type of sediment - kama
In addition to those that were mentioned earlier, there are other types of fluvioglacial deposits. For example, kama have interesting features. They, unlike the outwardly glacial species, are not formed due to the movement of the glacier, but are melt-washed sediments that once stopped here. Often the kams at their summit have swampy waters that do not have access to the ice bed.
In appearance, the kams resemble hills that are located at an altitude of 6 to 12 meters, while randomly scattered at these heights without revealing any order. When ice separates from the bulk of the glacier, it melts and forms these irregular hills. The latter feature is easily explained: the ice floes themselves are often of irregular shape, and uneven melting does not contribute to the creation of symmetrical figures. Kams are found in the Moscow, Leningrad and Kalinin regions in Russia.
Zandras - Complex Formations
Favorable soil for the formation of fluvioglacial deposits can be called terminal moraines and kama surrounding them outside the glacier. Pebbles, crushed stone, sand and gravel are deposited in powerful layers here. This is the zander. They add up to entire sandra fields, as deposits penetrate here through gentle slopes. The sandra fields have a central hollow where sediments pass into a cone-shaped funnel - meltwater left there, which brought sand and gravel in due time.
Over time, the sandra fields form an entire glacial series, complex in nature. It includes a transitional cone, moraine amphitheater (elevation), central hollow, oz and drumlins. This term was introduced by A. Penk and has a different name - the glacial complex. It is best seen on the example of a glacier cut along its width. There are many more new formations that can be distinguished in a separate row, 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 section in geology that interests not only researchers and scientists, but also engineers, architects, geologists and many other scientists. The study of these types of deposits can clarify a lot in the history of the formation of the glacier, the environment of that time and life.
Fluvioglacial materials are also valuable in the construction sense: stations, research laboratories, and technical buildings can only be designed and built on certain sections of glaciers. An important role is played by deposits in these places. One way or another, water-glacial sediments are an exciting research topic that many unfairly ignore.