Finchley Gap

The Finchley Gap is a topographical feature in North London and describes a band of relatively low-lying land linking the valley of the River Colne / River Lea, to the valley of the Mutton Brook, Dollis Brook, River Brent .

The primordial River Thames, followed a more northerly path than it does today along the valleys of the modern River Colne / River Lea . This channel is known to have been blocked by the large ice sheet that entered the Thames estuary during the Anglian glaciation . With its path to the sea blocked by ice this primordial river would have ponded back to form a periglacial lake. This would have eventually overflowed and found a new path to the sea. The Finchley gap is a hypothetical glacial drainage channel that carried the waters south during the Quaternary ice age when the valley of the primordial Thames was blocked by ice and moraines.

The Finchley gap is itself considered to have been blocked by later stages of the ice sheets advance known as the Anglian glaciation and a subsequent overflow channel then developed in the region of Staines which remains the course of the River Thames today.[1]

The Finchley feature was first detected and described by Professor Sidney Wooldridge (1938 and 1960), who dated it to the Anglian Stage glaciation around 450,000 BP, when ice and boulder clays advanced up the Thames valley as far as Bricket Wood in the northwest , Finchley in the west and Hornchurch to the south. Later work (by Moffat and Catt, 1982; Avery and Catt, 1983; Green and McGregor, 1983), which matched gravel deposits in the Vale of St Albans with those in the modern lower Thames valley suggests that the Finchley overflow route is unlikely.and that once ponded back by the ice the primordial Thames overflowed directly into its current route around Staines. [2]

The Mutton Brook, Dollis Brook, River Brent channels are more likely to have been cut by melt waters from the lobe of glacial ice that occupied Finchley when the ice sheets were at their maximum extent.