North of this ridge, between the valleys of the rivers Lea and Brent, lies a second ridge (a little under 100m), formed of much younger Pleistocene deposits. Running west from Muswell Hill to Church End, Finchley and north to Whetstone, this is capped by glacial till marking the southern limit of glaciation. This overlies "Dollis Hill Gravel" marking the line of a former southern tributary of the Thames, when the Thames flowed further to the north than it does today, through the Vale of St Albans. At its eastern end at Alexandra Palace the gravel forms the top of the ridge, as it does in smaller hills to the west including Dollis Hill itself.