In the north of Belarus, a huge lake existed — 150 times larger than Narach. It disappeared as a result of a natural disaster, but its traces are visible today

The area of the vast Narach, the largest lake in Belarus, is 150 times smaller than the area of the Polotsk proglacial lake, which splashed in the north of Belarus 11,000 years ago. Photo: golubyeozerabelarus.by

From the school curriculum, everyone knows that Narach is the largest lake in Belarus. Even flying in an airplane a hundred kilometers from the Belarusian borders, one can easily recognize two objects — the powerful cooling towers of the Belarusian NPP and the outlines of Narach. The lake's area of 79.6 km² may impress us, but compared to the body of water that existed nearby in the recent geological past, Narach is just a modest puddle.

If we had the opportunity to look at the territory of modern Belarus from a satellite in the Late Paleolithic era, we would see a colossal body of water in the north of the country, covering about 12,000 km².

Today, this lake would rank second in the list of the largest lakes in Europe, second only to Lake Ladoga, whose area is 17,870 km². Compared to the giant of the past, our modern Lake Narach is exactly 150 times smaller.

During its period of maximum filling, this gigantic water basin stretched from southwest to northeast for almost 200 km, also covering part of the territory of present-day Lithuania and Latvia. Maximum depths in the western, Dzisna part of the reservoir reached 70 meters, which is almost three times deeper than the deepest point of modern Narach.

How the sea appeared

To understand where such colossal water expanses came from, one must recall the last, Paazerian glacier. This mighty ice sheet began to gradually melt about 18,000 — 20,000 years ago under the influence of climatic warming. However, the water could not freely flow north, as its path was blocked by the glacier wall itself.

Павялічыць

Polotsk Lowland (dark green) on the geomorphological map of Belarus. Photo: Wikimedia Commons

From the south and east, uplands formed by previous glaciations served as a natural barrier. An ideal trap was formed, where meltwaters filled a gigantic depression (relief lowering), which we know today as the Polotsk Lowland.

The lake was poorly flowing. Excess water slowly flowed south, seeking a path through a system of through valleys into the Viliya and Berezina basins, and from there continued south into the Neman Lowland. For millennia, the gigantic basin remained a cold settling pond, at the bottom of which continuous layers of sand, pebbles, and varved clays accumulated.

The first people who lived in Belarus

For a long time, a myth prevailed in domestic historiography that the harsh north of Belarus in the Final Paleolithic was absolutely uninhabited, and the first hunters came here only in the Mesolithic era, when the climate finally softened. But recent archaeological data and a revision of old collections destroy these notions.

It turns out that life was bustling on the shores of the Polotsk Sea. Archaeologists find here traces of the so-called Swiderian culture — a community of reindeer hunters who possessed a sophisticated technique of flint processing. For example, at the Piasčanica site near Lake Lepel or in the Naŭry complex in the Myadzyel district, characteristic flint arrowheads and tools dating from 12,000 to 8,000 BCE have been found. Similar monuments are scattered at the same latitudes in neighboring Lithuania and Latvia.

This means that 11,000 years ago, when the lake was still splashing in the north of modern Belarus, ancient human settlements stood on its shores. They fished here, hunted in the coastal tundra and birch-pine woodlands, and it was they who witnessed the grandiose ecological catastrophe that changed the landscape forever.

The breakthrough of the Polotsk Sea into the Baltic Sea

The fate of the Polotsk Sea was predetermined by climatic changes. The gigantic body of water lasted for almost nine millennia, but its history ended during a period of sharp global warming, which geologists call the Allerød. As the glacier finally receded, the earth's crust, relieved of the weight of billions of tons of ice, began to rise.

Approximately 11,000 years ago, a powerful water stream finally found a weak spot in the moraine ridge to the west. This happened in the territory of modern Latvia, precisely in the section between the present-day cities of Krāslava and Dzvinsk (Daugavpils). The ancient Dvina literally broke through a natural dam, forming a through valley.

Millions of cubic meters of water, roaring wildly, rushed downwards, carving their way to the Baltic Sea. Perhaps it wasn't a scene from Hollywood disaster movies, where the current washes away all life in one day, but by geological standards, the descent occurred extremely rapidly.

Before the eyes of ancient hunters, the coastline began to recede instantly, and the gigantic basin emptied, leaving behind a muddy, bare landscape, which later became covered with dunes.

Traces of the Polotsk Sea today

Today's Polotsk Lowland is literally the dried-up bottom of that very sea. If you travel through the Vitebsk region and see absolutely flat plains that suddenly change into sandy aeolian ridges or hills, you are looking at the traces left by the currents of the Polotsk proglacial lake, and the remnants of its islands.

Павялічыць

Yelnya Swamp formed in shallow depressions from which the water of the Polotsk proglacial lake never fully drained. Photo bigtrip.by

The majestic pine forests along the Dvina are nourished precisely by those same lake-glacial sands. Extensive raised bogs, like the famous Yelnya or Obal massif, formed in shallow depressions from which the water never fully managed to drain.

Modern bodies of water, such as Lake Bahinskaje, remain only residual puddles of the former giant. The Dvina itself, with its numerous tributaries, including Drysa, Palata, and Dzisna, simply cut its new channels precisely through the soft sediments of the former sea.

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