Hańcza (; ) is a

lake A lake is often a naturally occurring, relatively large and fixed body of water on or near the Earth's surface. It is localized in a basin or interconnected basins surrounded by dry land. Lakes lie completely on land and are separate from ...

in Suwałki Region,

Podlaskie Voivodeship Podlaskie Voivodeship ( ) is a Voivodeships of Poland, voivodeship in northeastern Poland. The name of the voivodeship refers to the historical region of Podlachia (in Polish, ''Podlasie''), and significant part of its territory corresponds to th ...

Poland Poland, officially the Republic of Poland, is a country in Central Europe. It extends from the Baltic Sea in the north to the Sudetes and Carpathian Mountains in the south, bordered by Lithuania and Russia to the northeast, Belarus and Ukrai ...

. It is 311.4 ha large, 4.5 km long and 1.2 km at its widest. It is the deepest lake in Poland with a maximum depth of 108.5 m. The Czarna Hańcza river flows through it.

Geology of Lake Hańcza

Introduction Lake Hańcza, situated in the Suwałki region of northeastern Poland, is renowned not only for its depth (the deepest lake in

, reaching a maximum depth of approximately 108.5 meters) but also for its unique geological and limnological features. Geological analysis of this lake allows for an understanding of the processes that have shaped its current form and the structure of its substrata. Terrain Formation and Lake Genesis ''Glacial Origin'' Lake Hańcza was formed as a result of glacial activity during the

Pleistocene The Pleistocene ( ; referred to colloquially as the ''ice age, Ice Age'') is the geological epoch (geology), epoch that lasted from to 11,700 years ago, spanning the Earth's most recent period of repeated glaciations. Before a change was fin ...

epoch. Like many post-glacial lakes, Hańcza owes its existence to the last Baltic glaciation. Melting ice left behind various landforms, including glacial troughs, which filled with water, creating lakes. Subglacial Channel Lake Hańcza is an example of a ribbon lake, formed by the erosive activity of subglacial waters. These waters flowed under immense pressure beneath the ice sheet, carving deep channels into the substrate. These channels later filled with water, forming present-day lakes. Hańcza has a characteristic elongated shape, typical of ribbon lakes, indicating its glacial origin. Stratigraphy and Lithology of the Region The geological structure of the Suwałki region, including the area of Lake Hańcza, is complex and encompasses layers ranging from the Precambrian to the

Quaternary The Quaternary ( ) is the current and most recent of the three periods of the Cenozoic Era in the geologic time scale of the International Commission on Stratigraphy (ICS), as well as the current and most recent of the twelve periods of the ...

. The region is predominantly composed of metamorphic and

igneous rocks Igneous rock ( ), or magmatic rock, is one of the three main Rock (geology)#Classification, rock types, the others being sedimentary rock, sedimentary and metamorphic rock, metamorphic. Igneous rocks are formed through the cooling and solidifi ...

, particularly in the northern part, where gneisses and granites are found. The substrate of Lake Hańcza mainly consists of glacial deposits: till, sands, gravels, and silts. Numerous glacial erratics, brought by the glacier from distant regions of Scandinavia, can be found on its floor. Morphology of the Lake Bed ''Lake Bed'' The bottom of Lake Hańcza is characterized by a complex morphology, resulting from various sedimentary and erosive processes. The deepest parts of the lake feature steep slopes, which may indicate landslide activity. The lake bed also contains structures formed by glacial activity, such as drumlins and kames. ''Sedimentary Processes'' Sedimentation in Lake Hańcza is a dynamic process. Organic sediments, primarily derived from fallen leaves and plant matter, as well as mineral sediments carried by surface waters, accumulate on the lake bed. In the central part of the lake, sediments are finer-grained, indicating calmer deposition conditions. Mizerski Włodzimierz: Geologia Polski. Wydawnictwo Naukowe PWN, 2020

References

Lakes of Podlaskie Voivodeship Underwater diving sites in Poland Suwałki County {{Suwałki-geo-stub