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- The Finchley Gap (or "Finchley depression") is a location centred on Church End, Finchley, in north London, England. As a topographical feature approximately eight kilometres wide, lying between higher ground to the north-west (Mill Hill) and to the south-east (Hampstead Heath), it has probably existed for the last one million years or more. The Finchley Gap has lower ground to the north-east (the catchment area of the River Lea), and the south-west (the catchment area of the River Brent). The North Circular Road (A406) passes over the Gap, from one catchment area to the other. The geolgical history of the Finchey Gap, and its place in the history of academic research, makes it one of the most interesting topographical features of the London area. The principal geological formation in the Finchley Gap region, as in much of the London Basin, is Eocene London Clay. This is mostly a stiff blue-brown clay, over 100 metres thick. In parts of this region, a relatively thin, upper part of the London Clay formation, sandier in content and known as the Claygate Beds, is also found. In certain areas of relatively limited extent, such as on the higher parts of Harrow on the Hill, Hampstead and Highgate, the London Clay and Claygate Beds are overlain by sandy Eocene Bagshot Beds. All these formations are overlain in several areas by much younger Pleistocene formations, as explained below. From 1938 until the 1960s, it was supposed that the River Thames once flowed through the Gap, along the line of a "Middlesex loopway" running from somewhere around Harefield to the Hoddesdon-Ware area. This supposition was later shown to be erroneous. Prior to the Anglian glaciation, the "proto-Mole-Wey"river, a then south bank tributary of the "proto-Thames", flowed northwards from the Weald, through Richmond and the Finchley Gap, to the Hoddesdon-Ware area. There, it joined the proto-Thames (which at that time was flowing north-eastwards, through the Vale of St Albans). About 450,000 years ago, a lobe of the Anglian ice sheet advanced up the valley of the proto-Mole-Wey at least as far south as the Finchley Gap. There, the ice left glacial drift which today is up to 18 metres in thickness. Another lobe of the Anglian ice sheet moved up the Vale of St Albans, thus diverting the Thames southwards. When this happened, the proto-Mole-Wey was cut off at Richmond. The Finchley Gap now lies on the watershed of the catchment areas of the Rivers Brent and Lea, both south-flowing tributaries of the Thames. (en)
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| rdfs:comment
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- The Finchley Gap (or "Finchley depression") is a location centred on Church End, Finchley, in north London, England. As a topographical feature approximately eight kilometres wide, lying between higher ground to the north-west (Mill Hill) and to the south-east (Hampstead Heath), it has probably existed for the last one million years or more. The Finchley Gap has lower ground to the north-east (the catchment area of the River Lea), and the south-west (the catchment area of the River Brent). The North Circular Road (A406) passes over the Gap, from one catchment area to the other. (en)
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