Ancylus lake is a name given by geologists to the body of fresh water that replaced the
Yoldia SeaYoldia Sea is a name given by geologists to a variable brackish-water stage in the Baltic Sea basin that prevailed after the Baltic ice lake was drained to sea level during the Weichsel glaciation...
after the latter had been severed from its saline intake across central
SwedenSweden , officially the Kingdom of Sweden , is a Nordic country on the Scandinavian Peninsula in Northern Europe...
(with the eastern end of the channel near present Stockholm) by the isostatic rise of south
ScandinaviaScandinavia is a geographical region in northern Europe that includes, and is named after, the Scanian Province. It consists of the kingdoms of Norway, Sweden, and Denmark...
n landforms. The dates are approximately 9500-8000 BP calibrated, during the full
Boreal periodIn paleoclimatology of the Holocene, the Boreal was the first of the Blytt-Sernander sequence of north European climatic phases that were originally based on the study of Danish peat bogs, named for Axel Blytt and Rutger Sernander, who first established the sequence. In peat bog sediments, the...
. The lake became
Littorina SeaLittorina Sea is a geological brackish-water stage of the Baltic Sea, which existed around 7500–4000 BP and followed the Mastogloia Sea, transitional stage of the Ancylus Lake...
when rising oceanic levels broke through the
Great BeltThe Great Belt is a strait between the main Danish islands of Zealand and Funen . Effectively dividing Denmark in two, the Belt was trafficked by the Great Belt ferries from the late 19th century until the islands were connected by the Great Belt Fixed Link in 1997–98.-Geography:The Great Belt is...
.
The lake was named by
Gerard de GeerBaron Gerard Jacob De Geer was a Swedish geologist who made significant contributions to Quaternary geology, particularly geomorphology and geochronology. De Geer is best known for his discovery of varves.- Early life and family :...
after
Ancylus fluviatilisAncylus fluviatilis is a species of very small, freshwater, air-breathing limpet, an aquatic pulmonate gastropod mollusk in the tribe Ancylini within the family Planorbidae, the ram's horn snails and their allies.-Distribution and conservation status:...
, a gastropod found in its
sedimentSediment is any particulate matter that can be transported by fluid flow, and which eventually is deposited.Sediments are most often transported by water transported by wind and glaciers...
s.
The elevation of southern Sweden did not entirely block the flow across central Sweden.
Ancylus lake is a name given by geologists to the body of fresh water that replaced the
Yoldia SeaYoldia Sea is a name given by geologists to a variable brackish-water stage in the Baltic Sea basin that prevailed after the Baltic ice lake was drained to sea level during the Weichsel glaciation...
after the latter had been severed from its saline intake across central
SwedenSweden , officially the Kingdom of Sweden , is a Nordic country on the Scandinavian Peninsula in Northern Europe...
(with the eastern end of the channel near present Stockholm) by the isostatic rise of south
ScandinaviaScandinavia is a geographical region in northern Europe that includes, and is named after, the Scanian Province. It consists of the kingdoms of Norway, Sweden, and Denmark...
n landforms. The dates are approximately 9500-8000 BP calibrated, during the full
Boreal periodIn paleoclimatology of the Holocene, the Boreal was the first of the Blytt-Sernander sequence of north European climatic phases that were originally based on the study of Danish peat bogs, named for Axel Blytt and Rutger Sernander, who first established the sequence. In peat bog sediments, the...
. The lake became
Littorina SeaLittorina Sea is a geological brackish-water stage of the Baltic Sea, which existed around 7500–4000 BP and followed the Mastogloia Sea, transitional stage of the Ancylus Lake...
when rising oceanic levels broke through the
Great BeltThe Great Belt is a strait between the main Danish islands of Zealand and Funen . Effectively dividing Denmark in two, the Belt was trafficked by the Great Belt ferries from the late 19th century until the islands were connected by the Great Belt Fixed Link in 1997–98.-Geography:The Great Belt is...
.
The lake was named by
Gerard de GeerBaron Gerard Jacob De Geer was a Swedish geologist who made significant contributions to Quaternary geology, particularly geomorphology and geochronology. De Geer is best known for his discovery of varves.- Early life and family :...
after
Ancylus fluviatilisAncylus fluviatilis is a species of very small, freshwater, air-breathing limpet, an aquatic pulmonate gastropod mollusk in the tribe Ancylini within the family Planorbidae, the ram's horn snails and their allies.-Distribution and conservation status:...
, a gastropod found in its
sedimentSediment is any particulate matter that can be transported by fluid flow, and which eventually is deposited.Sediments are most often transported by water transported by wind and glaciers...
s.
Description
The elevation of southern Sweden did not entirely block the flow across central Sweden. Some egress continued from the lake through the
GötaThe Göta älv is a river that drains lake Vänern into Kattegat at the city of Gothenburg on the western coast of Sweden. It is located in Götaland, with the river itself being a site of early Geatish settlement. The length is 93 km. Often the combination of Göta älv and Klarälven is mentioned...
and Steinselva rivers, which exit Lake Vänern to the
KattegatThe Kattegat , or Kattegatt is a sea area bounded by Jutland , and Scania, Halland and Bohuslän . The Baltic Sea drains into the Kattegat through the Oresund and the Danish Straits...
. Salt water did not enter the lake, however, which became entirely fresh as the lake rose above sea level. The date at which the flow was certainly blocked is about 8000 BP, when nearby Lake
VätternVättern is the second largest lake in Sweden, after Lake Vänern. It is a long, finger-shaped body of fresh water in south central Sweden to the southeast of Vänern pointing at the tip of Scandinavia.-Name:...
(part of the waterway system) became dissevered from Ancylus lake.
The result of increasing lake levels was the Ancylus transgression, a general flooding around its shores, 9500-9200 BP. By this time a somewhat larger
Gulf of BothniaThe Gulf of Bothnia is the northernmost arm of the Baltic Sea. It is situated between Finland's west coast and Sweden's east coast. In the south of the gulf lie the Åland Islands, between the Sea of Åland and the Archipelago Sea.-Name:...
and parts of
NorwayNorway , officially the Kingdom of Norway, is a country in Northern Europe occupying the western portion of the Scandinavian Peninsula, as well as Jan Mayen and the Arctic archipelago of Svalbard under the Spitsbergen Treaty...
were free of ice, while the
RovaniemiRovaniemi is a city and municipality of Finland. It is the administrative capital and the centre of commerce of Finland's northernmost Province, Lapland. It is situated close to the Arctic Circle and between the hills of Ounasvaara and Korkalovaara, at the confluence of the Kemijoki River and its...
region of
FinlandFinland , officially the Republic of Finland
, is a Nordic country and democracy situated in the Fennoscandian region of northern Europe. It borders Sweden on the west, Russia on the east, and Norway on the north, while Estonia lies to its south across the Gulf of Finland...
appeared no later than 9000 BP, despite the new flooding.
Accelerated melting and landforms rebounding at different rates in different locations led to some instability. By 9200 BP the lake rose over the Dars sill and cut a new channel in the vicinity of what is now the "
Great BeltThe Great Belt is a strait between the main Danish islands of Zealand and Funen . Effectively dividing Denmark in two, the Belt was trafficked by the Great Belt ferries from the late 19th century until the islands were connected by the Great Belt Fixed Link in 1997–98.-Geography:The Great Belt is...
" (the channel between the Danish islands Zealand and Funen), which some geologists call the Dana River. For a time, Skåne, or southern Sweden, was an island once more, from about 9200 to no later than 8000 BP. The lake level began to drop.
North Scandinavia
By 9000 BP the northern channel ceased functioning, joining Skåne to Scandinavia rather than to Denmark. However, only an isthmus connected Skåne to the new northern lands. If Skåne acquired its designation as an island on a geographic basis, it must have been no later than the Ancylus lake phase. At that time
MesolithicThe Mesolithic or "Middle Stone Age" was a period in the development of human technology in between the Paleolithic or Old Stone Age and the Neolithic or New Stone Age. The term was introduced by John Lubbock in his work Pre-historic Times, published in 1865. The term was, however, not much used...
cultures moved into newly released land around the shores of the
Gulf of BothniaThe Gulf of Bothnia is the northernmost arm of the Baltic Sea. It is situated between Finland's west coast and Sweden's east coast. In the south of the gulf lie the Åland Islands, between the Sea of Åland and the Archipelago Sea.-Name:...
. They were fishing along the shores, hunting seals and following the reindeer into their new ranges.
In Lapland Mesolithic fishers, hunters and probably herders found pine-birch forest with tundra-like open spaces. In addition to pinus and betula were
aspenAspen is a common name for trees of the Salicaceae family, most of those in a section, Populus sect. Populus, of the Populus genus. Some of the species in the section are:...
,
alderAlder is the common name of a genus of flowering plants belonging to the birch family . The genus comprises about 30 species of monoecious trees and shrubs, few reaching large size, distributed throughout the North Temperate Zone and in the Americas also along the Andes southwards to...
,
willowWillows, sallows, and osiers form the genus Salix, around 400 species of deciduous trees and shrubs, found primarily on moist soils in cold and temperate regions of the Northern Hemisphere...
,
crowberriesCrowberry is a small genus of dwarf evergreen shrubs that bear edible fruit. They are commonly found in the northern hemisphere, from temperate to subarctic climates, and also in the Andes of South America and on Tristan da Cunha . The typical habitat is on moorlands, tundra and muskeg, but also...
,
grassGrasses, or more technically graminoids, are monocotyledonous, usually herbaceous plants with narrow leaves growing from the base. They include the "true grasses", of the Poaceae family, as well as the sedges and the rushes . The true grasses include cereals, bamboo and the grasses of lawns...
and
sedgeCyperaceae is a family of monocot flowering plants known as sedges, which superficially resemble grasses or rushes. The family is large, with some 4,000 species described in about 70 genera. These species are widely distributed, with the centers of diversity for the group occurring in tropical...
. Much of the new Finnish land was covered by
mireA poor fen is a natural wetland habitat, consisting of dense low growth of small sedges and other plants...
.
MoraineA moraine is any glacially formed accumulation of unconsolidated glacial debris which can occur in currently glaciated and formerly glaciated regions, such as those areas acted upon by a past ice age. This debris may have been plucked off the valley floor as a glacier advanced or it may have...
ridges and
drumlinA drumlin is an elongated whale-shaped hill formed by glacial action. Its long axis is parallel with the movement of the ice, with the blunter end facing into the glacial movement...
s formed an extensive island system. The shores around the lake were stony ground.