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The Curonian Lagoon is inseparable from the Baltic Sea. The
geological evolution of the Curonian Spit has a short but rich history.
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| THE DEVELOPMENT OF THE BALTIC SEA AND THE CURONIAN
LAGOON |
The development of the Baltic Sea started after the retreat
of the last glacier, which covered entire Europe. This process started 18 000
or 20 000 years ago. Thirteen thousand years ago the glacier left Lithuania completely.
Its melting waters filled the Baltic pit and a large cold Baltic Glacial Lake
appeared, which merged with the Atlantic Ocean several times. This lake existed
between 13 000 and 10 000 years ago.
After some time, the glacier drifted from the middle of Sweden; the Baltic Glacier
Lake adjoined the Atlantic Ocean. When the glacier moved on once again, the water
level started to rise and it dropped about 40 or 50 metres when the fringe of
the glacier moved away. Large dry areas appeared and the Yoldian Sea formed.
It got its name from the molluscs Yoldia arctica, which were very abundant. The
shore of the Yoldian Sea was much farther West from the present Lithuanian coast.
When the earth crust started to rise in the southern part of the Baltic Basin,
the link between the Yoldian Sea and the ocean broke. River flow decreased the
salinity and the water level rose. Thus eventually the fresh water Ancyliaus
Lake formed approximately 9 000 years ago. It got its name from the mollusc
Ancylus fluviatilis. The climate then was warm and dry. Sediments of this lake
are found near Nida in depths of 16-18 m.
Approximately 7 500 years ago with the earth crust gradually sinking the salty
water of the Atlantic Ocean broke into Ancyliaus Lake and the Litorinal Sea
formed (name comes from the mollusc Littorina littoraea). Water level in the sea
fluctuated many times during this stage and the formation of the Curonian Spit
started. Its inception was a morainic ridge with the peaks at Sarkuva and Rasyte
islands. At that time sea waves intensively washed the Sambian Peninsula. The
prevailing sea streams carried the outwashed sediments along the coast to the
North and dropped them near Sarkuva and Rasyte islands. In a short time the growing
Curonian Spit isolated the lagoon from the sea. It is concluded that formation
of both the Curonian Spit and the Lagoon started approximately 5 000 years ago.
The development of the present Curonian Spit started to the North from the Semba
Peninsula. Moving dunes covered the morainic ground and the swamp, remains of
which nowadays appear as Sentlunka raised bog. Sand started to accumulate at Sarkuva
and Rasyte islands, which were a natural barrier. Soon they joined the continent.
Further growth of the spit went to the North and to the South. This process developed
rather quickly and 4 500 or 4000 years ago the Curonian Spit reached the place
where Juodkrante is presently located. Sand excess and prevailing west winds formed
the cross relief of the Curonian Spit. Sand hillocks at the seacoast were growing
and the wind turned them into dunes, which were moving across the peninsula, making
it wider. At the same time the peninsula moved eastward. Today the Curonian Spit
is 1 to 2 km closer to the continent than at the beginning. At the end of the
Litorinal Sea stage, the parabolic dunes were formed in the spit. They got their
name because of their shape. It was not finally clear until now how the parabolic
dunes formed and how the barchan, which are like the mirror reflection of parabolic
dunes. One area with parabolic dunes is located near Juodkrante. These dunes were
overgrown by the forest and didn't move any more. Fragments of the old growth
forest are preserved there.
Four thousand years ago the Baltic Sea gained its present appearance. The salinity
decreased and present fauna and flora became prevalent. The spit from Juodkrante
to the very end of Kopgalis accumulated sand, which was supplied by the prevailing
southwest sea streams. This part of the spit grew much slower and present its
length reached only 2 000 years ago. The channel from the Curonian Lagoon to the
Baltic Sea formed at the same time. Landscapes in the Curonian Spit were different
from the present picture. Vegetation covering parabolic dunes prevailed. They
were from 30 to 40 m high and some reached 60 m above sea level. The entire surface
was carved with hollows and ridges. Mixed forest with oaks, lindens, elms, pines,
birches, alders and hazelnuts dominated. Sometimes fires destroyed the forest
cover and the sand drifting started. Later in time the forest recovered. Such
a natural harmony lasted till the 16th century, when negative human impact to
the Curonian Spit started to grow. |
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Baltic Glacial Lake
Yoldia Sea
Ancylus Lake
Littorina Sea
The model of parabolic dunes
Parabolic dunes and fragment of the oldgrowth forest
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