The Outer Silver Pit is a west-to-east valley in the bed of the

North Sea The North Sea lies between Great Britain, Denmark, Norway, Germany, the Netherlands, Belgium, and France. A sea on the European continental shelf, it connects to the Atlantic Ocean through the English Channel in the south and the Norwegian Se ...

. Its widest part is east of

Flamborough Head Flamborough Head () is a promontory, long on the Yorkshire coast of England, between the Filey and Bridlington bays of the North Sea. It is a chalk headland, with sheer white cliffs. The cliff top has two standing lighthouse towers, the olde ...

England England is a Countries of the United Kingdom, country that is part of the United Kingdom. It is located on the island of Great Britain, of which it covers about 62%, and List of islands of England, more than 100 smaller adjacent islands. It ...

. It is between the

Dogger Bank Dogger Bank ( Dutch: ''Doggersbank'', German: ''Doggerbank'', Danish: ''Doggerbanke'') is a large sandbank in a shallow area of the North Sea about off the east coast of England. During the last ice age, the bank was part of a large landmass ...

and the ridge dividing the northern from the southern North Sea basins, which runs between

Norfolk Norfolk ( ) is a Ceremonial counties of England, ceremonial county in England, located in East Anglia and officially part of the East of England region. It borders Lincolnshire and The Wash to the north-west, the North Sea to the north and eas ...

and

Friesland Friesland ( ; ; official ), historically and traditionally known as Frisia (), named after the Frisians, is a Provinces of the Netherlands, province of the Netherlands located in the country's northern part. It is situated west of Groningen (p ...

. When the sea level was lower (such as in the

Ice Age An ice age is a long period of reduction in the temperature of Earth's surface and atmosphere, resulting in the presence or expansion of continental and polar ice sheets and alpine glaciers. Earth's climate alternates between ice ages, and g ...

) it was a lake in

Doggerland Doggerland was a large area of land in Northern Europe, now submerged beneath the southern North Sea. This region was repeatedly exposed at various times during the Pleistocene epoch due to the lowering of sea levels during glacial periods. Howe ...

, and sea-bed-penetrating sonar

bathymetry Bathymetry (; ) is the study of underwater depth of ocean floors ('' seabed topography''), river floors, or lake floors. In other words, bathymetry is the underwater equivalent to hypsometry or topography. The first recorded evidence of wate ...

has found its shorelines and courses and estuaries of rivers that ran into it from the high land of the

; it overflowed into a river at its west end.''Mapping

'', ed. Vincent Gaffney and others, publ. Archaeopres

2007,

Bed of the Rhine?

In the

Cromerian Stage The Cromerian Stage or Cromerian Complex, also called the Cromerian (), is a stage in the Pleistocene glacial history of north-western Europe, mostly occurring more than half a million years ago. It is named after the East Anglian town of Cromer in ...

, before more recent glaciation had influenced the area, a ridge of high ground, the Weald-Artois Anticline, joined the

Upper Cretaceous The Late Cretaceous (100.5–66 Ma) is the more recent of two epochs into which the Cretaceous Period is divided in the geologic time scale. Rock strata from this epoch form the Upper Cretaceous Series. The Cretaceous is named after ''cret ...

chalk Chalk is a soft, white, porous, sedimentary carbonate rock. It is a form of limestone composed of the mineral calcite and originally formed deep under the sea by the compression of microscopic plankton that had settled to the sea floor. Ch ...

Kent Kent is a Ceremonial counties of England, ceremonial county in South East England. It is bordered by Essex across the Thames Estuary to the north, the Strait of Dover to the south-east, East Sussex to the south-west, Surrey to the west, and Gr ...

to that of the Boulonnais at '' Cap Blanc-Nez'' in the

Pas de Calais The Strait of Dover or Dover Strait, historically known as the Dover Narrows, is the strait at the narrowest part of the English Channel, marking the boundary between the Channel and the North Sea, and separating Great Britain from continental ...

France France, officially the French Republic, is a country located primarily in Western Europe. Overseas France, Its overseas regions and territories include French Guiana in South America, Saint Pierre and Miquelon in the Atlantic Ocean#North Atlan ...

. It is possible that in the Cromerian Stage, the Outer Silver Pit was the bed of the combined Maas,

Rhine The Rhine ( ) is one of the List of rivers of Europe, major rivers in Europe. The river begins in the Swiss canton of Graubünden in the southeastern Swiss Alps. It forms part of the Swiss-Liechtenstein border, then part of the Austria–Swit ...

Scheldt The Scheldt ( ; ; ) is a river that flows through northern France, western Belgium, and the southwestern part of Netherlands, the Netherlands, with its mouth at the North Sea. Its name is derived from an adjective corresponding to Old Englis ...

and

Thames The River Thames ( ), known alternatively in parts as the River Isis, is a river that flows through southern England including London. At , it is the longest river entirely in England and the second-longest in the United Kingdom, after th ...

. Since at that stage, the Weald-Artois Anticline had probably not been breached by the

glacial lake outburst flood A glacial lake outburst flood (GLOF) is a type of outburst flood caused by the failure of a dam containing a glacial lake. An event similar to a GLOF, where a body of water contained by a glacier melts or overflows the glacier, is called a j� ...

s that scoured the Strait of Dover, the southern North Sea basin held a freshwater lake impounded by the ridge of the Weald-Artois Anticline and by the Norfolk-Friesland ridge. Whether the lake spilled north through the Outer Silver Pit would depend on how much the modern sea bed to the north has been raised by later marine and glacial sediment, and how much the various parts of the area were raised by

forebulge In geology, a forebulge is a flexural bulge in front as a result of a load on the lithosphere, often caused by Tectonics, tectonic interactions and glaciations. An example of forebulge can be seen in the Himalayan foreland basin, a result of the In ...

effect caused by the weight of the Scandinavian ice cap. The east end of the Outer Silver Pit is in line with the lowest part of the Norfolk-Friesland ridge. The outlet at the western end of the pit appears to be blocked by somewhat higher ground.

Bed of the Urstrom?

There is an older theory that the Outer Silver Pit was part of the valley of the great ice-age river

Urstrom The Urstrom is a geologists' name for a great glacial age river of the Polish and north German plain, which drained the combined melt-waters from the northern headwaters of the Alps and the southern part of the Scandinavian ice during the Devens ...

, during some of the Ice Ages when the Scandinavian ice did not meet the British ice, leaving the North Sea bed with open drainage northwards. Maps by some geologists show rivers from the German part of the Urstrom's catchment area flowing northwards east of the

highland area; but Scandinavian ice reaching the Dogger Bank would have forced the Urstrom into another route. When the Scandinavian and Scottish ice caps first met, the Urstrom (unless it found a way northwards under the ice) would have backed up into a huge lake in the southern North Sea, which finally found an outlet southwards over the Weald-Artois Anticline and helped to cut the valley of the Strait of Dover: see Strait of Dover#Geological formation.

References

*Benn, D.I. & Evans, D.J.A. ''Glaciers and Glaciation'' (1998) *Cameron, Crosby, Balson, Jeffery, Lott, Bulat & Harrison. ''The Geology of the Southern North Sea'' (1992) *Glennie, K.W. ''Lower Permian - Rotliegend'' in ed. Glennie ''Introduction to the Petroleum Geology of the North Sea''. (1990) {{ISBN, 0-632-02711-8 *Imray, Laurie, Norie & Wilson pub. ''East Coast of England: Orfordness to Blythe'' marine chart (1980) Landforms of the North Sea

Bed of the Rhine?

Bed of the Urstrom?

See also

References