The Ancestral Thames is the geologically ancient precursor to the present day

River Thames The River Thames ( ), known alternatively in parts as the The Isis, River Isis, is a river that flows through southern England including London. At , it is the longest river entirely in England and the Longest rivers of the United Kingdom, se ...

Relationships with other rivers

During the Early and Middle

Pleistocene The Pleistocene ( , often referred to as the ''Ice age'') is the geological Epoch (geology), epoch that lasted from about 2,580,000 to 11,700 years ago, spanning the Earth's most recent period of repeated glaciations. Before a change was fina ...

, central and southern Britain had two main rivers of more than : the Bytham and the Ancestral Thames. For most of the Early Pleistocene the Ancestral Thames was the main river with, at its maximum extent, a

catchment area In human geography, a catchment area is the area from which a location, such as a city, service or institution, attracts a population that uses its services and economic opportunities. Catchment areas may be defined based on from where people are ...

that extended into

Wales Wales ( cy, Cymru ) is a Countries of the United Kingdom, country that is part of the United Kingdom. It is bordered by England to the Wales–England border, east, the Irish Sea to the north and west, the Celtic Sea to the south west and the ...

alongside the

Chiltern Hills The Chiltern Hills is a chalk escarpment in England. The area, northwest of London, covers stretching from Goring-on-Thames in the southwest to Hitchin in the northeast - across Oxfordshire, Buckinghamshire, Hertfordshire, and Bedfordshire. ...

, through southern

East Anglia East Anglia is an area in the East of England, often defined as including the counties of Norfolk, Suffolk and Cambridgeshire. The name derives from the Anglo-Saxon kingdom of the East Angles, a people whose name originated in Anglia, in ...

and finally into

Doggerland Doggerland was an area of land, now submerged beneath the North Sea, that connected Britain to continental Europe. It was flooded by rising sea levels around 6500–6200 BCE. The flooded land is known as the Dogger Littoral. Geological sur ...

(now the North Sea), where it joined the Ancestral Rhine. In the early Ice Age the Thames took a line similar to the present-day

River Thame The River Thame is a river in Southern England. A tributary of the River Thames, the river runs generally south-westward for about from its source above the Buckinghamshire town of Aylesbury to the Thames in south-east Oxfordshire. Course Thr ...

, through parts of

Bedfordshire Bedfordshire (; abbreviated Beds) is a ceremonial county in the East of England. The county has been administered by three unitary authorities, Borough of Bedford, Central Bedfordshire and Borough of Luton, since Bedfordshire County Council wa ...

Hertfordshire Hertfordshire ( or ; often abbreviated Herts) is one of the home counties in southern England. It borders Bedfordshire and Cambridgeshire to the north, Essex to the east, Greater London to the south, and Buckinghamshire to the west. For govern ...

and north-west

Essex Essex () is a county in the East of England. One of the home counties, it borders Suffolk and Cambridgeshire to the north, the North Sea to the east, Hertfordshire to the west, Kent across the estuary of the River Thames to the south, and G ...

, then took a course resembling that of the

River Waveney The River Waveney is a river which forms the boundary between Suffolk and Norfolk, England, for much of its length within The Broads. The "ey" part of the name means "river" thus the name is tautological. Course The source of the River Wavene ...

along the

Suffolk Suffolk () is a ceremonial county of England in East Anglia. It borders Norfolk to the north, Cambridgeshire to the west and Essex to the south; the North Sea lies to the east. The county town is Ipswich; other important towns include Lowes ...

Norfolk Norfolk () is a ceremonial and non-metropolitan county in East Anglia in England. It borders Lincolnshire to the north-west, Cambridgeshire to the west and south-west, and Suffolk to the south. Its northern and eastern boundaries are the No ...

border. Initially the more northerly Bytham River was a

tributary A tributary, or affluent, is a stream or river that flows into a larger stream or main stem (or parent) river or a lake. A tributary does not flow directly into a sea or ocean. Tributaries and the main stem river drain the surrounding drainage ...

of the Thames but as the climate warmed it progressively extended its catchment. During the

Anglian Stage The Anglian Stage is the name used in the British Isles for a middle Pleistocene glaciation. It precedes the Hoxnian Stage and follows the Cromerian Stage in the British Isles. The Anglian Stage is correlated to Marine Isotope Stage 12 (MIS 12), ...

the Bytham river more or less disappeared and the Thames was diverted to its present course through

London London is the capital and largest city of England and the United Kingdom, with a population of just under 9 million. It stands on the River Thames in south-east England at the head of a estuary down to the North Sea, and has been a majo ...

Loubourg River system

During the last

glacial maximum 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 gree ...

, much of what is now the southern part of the

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

was land, known to

palaeogeographer Palaeogeography (or paleogeography) is the study of historical geography, generally physical landscapes. Palaeogeography can also include the study of human or cultural environments. When the focus is specifically on landforms, the term pal ...

s as

. At this time, the

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 the R ...

, the

Meuse The Meuse ( , , , ; wa, Moûze ) or Maas ( , ; li, Maos or ) is a major European river, rising in France and flowing through Belgium and the Netherlands before draining into the North Sea from the Rhine–Meuse–Scheldt delta. It has a t ...

, the

Scheldt The Scheldt (french: Escaut ; nl, Schelde ) 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 corr ...

and the

Rhine ), Surselva, Graubünden, Switzerland , source1_coordinates= , source1_elevation = , source2 = Rein Posteriur/Hinterrhein , source2_location = Paradies Glacier, Graubünden, Switzerland , source2_coordinates= , so ...

probably joined before flowing into the sea, in a system known as the Loubourg or Lobourg River. There is some debate as to whether this river would have flowed south-west into what is now the

English Channel The English Channel, "The Sleeve"; nrf, la Maunche, "The Sleeve" (Cotentinais) or ( Jèrriais), (Guernésiais), "The Channel"; br, Mor Breizh, "Sea of Brittany"; cy, Môr Udd, "Lord's Sea"; kw, Mor Bretannek, "British Sea"; nl, Het Kana ...

, or north into the North Sea close to modern

Yorkshire Yorkshire ( ; abbreviated Yorks), formally known as the County of York, is a Historic counties of England, historic county in northern England and by far the largest in the United Kingdom. Because of its large area in comparison with other Eng ...

. Current scientific research favours the former opinion, with the Thames and Rhine meeting in a large lake, the outflow of which was close to the present-day

Straits of Dover The Strait of Dover or Dover Strait (french: Pas de Calais - ''Strait of Calais''), is the strait at the narrowest part of the English Channel, marking the boundary between the Channel and the North Sea, separating Great Britain from continent ...

Vestiges

Before its diversion, this river and its tributaries formed a river system draining the Welsh mountains and bringing some of their characteristic

volcanic rocks Volcanic rock (often shortened to volcanics in scientific contexts) is a Rock (geology), rock formed from lava erupted from a volcano. In other words, it differs from other igneous rock by being of Volcano, volcanic origin. Like all rock types, ...

into this area. The evidence for this is a substantial thickness of what is called Kesgrave Sands and Gravels which represent the bed of the river. These old Thames gravels contain a variety of distinctive pebbles from as far away as North Wales, evidence of the ancient drainage catchment. The gravels also contain large

boulders In geology, a boulder (or rarely bowlder) is a rock fragment with size greater than in diameter. Smaller pieces are called cobbles and pebbles. While a boulder may be small enough to move or roll manually, others are extremely massive. In co ...

of puddingstone and sarsens, which are very hard conglomerates and

sandstones Sandstone is a clastic sedimentary rock composed mainly of sand-sized (0.0625 to 2 mm) silicate grains. Sandstones comprise about 20–25% of all sedimentary rocks. Most sandstone is composed of quartz or feldspar (both silicates) b ...

respectively. They are believed to be derived from pebble and sand seams in the

Reading Beds The Reading Formation is a geologic formation in southern England. It dates to the Paleocene period, and is part of the Lambeth Group. It overlies the London Basin and is below the Harwich Formation. The formation is composed of "a series of lent ...

(subsequently cemented by

quartz Quartz is a hard, crystalline mineral composed of silica (silicon dioxide). The atoms are linked in a continuous framework of SiO4 silicon-oxygen tetrahedra, with each oxygen being shared between two tetrahedra, giving an overall chemical form ...

). They have been put to use by man as ancient way markers at road junctions. The gravels have great commercial value and are worked in numerous pits between Harlow, Chelmsford and Colchester, where the ancestral Thames flowed at least 600,000 years ago. During this time the River Medway flowed north across east Essex to join the Thames near Clacton, leaving behind a ribbon of distinctive gravel which can be found between

Burnham-on-Crouch Burnham-on-Crouch is a town and civil parish in the Maldon District of Essex in the East of England. It lies on the north bank of the River Crouch. It is one of Britain's leading places for yachting. The civil parish extends east of the town t ...

and

Bradwell-on-Sea Bradwell-on-Sea is a village and civil parish in Essex, England. The village is on the Dengie peninsula. It is located about north-northeast of Southminster and is east from the county town of Chelmsford. The village is in the District of Mald ...

. There were also other northward-flowing tributaries of the early Thames. Evidence of these are the patches of gravel that are found near the tops of the modest hills in south Essex, principally the

Langdon Hills Langdon Hills is a township and former civil parish located in Basildon in Essex, England. It is located south of Laindon railway station on the London, Tilbury and Southend line. It is the location of the Langdon Hills Country Park, which is ...

, Warley and High Beach in

Epping Forest Epping Forest is a area of ancient woodland, and other established habitats, which straddles the border between Greater London and Essex. The main body of the forest stretches from Epping in the north, to Chingford on the edge of the London ...

References

{{reflist Geology of England Former rivers Rivers of England River Thames