Oak Ridges Moraine

The Oak Ridges Moraine is an ecologically important geological landform in the Mixedwood Plains of south-central Ontario, Canada. The moraine covers a geographic area of 1,900 square kilometres (730 sq mi) between Caledon and Rice Lake, near Peterborough. One of the most significant landforms in southern Ontario, the moraine gets its name from the rolling hills and river valleys extending 160 km (99 mi) from the Niagara Escarpment east to Rice Lake. It was formed 12,000 years ago by advancing and retreating glaciers (see geological origins, below). The moraine is currently a contested site in Ontario, since it stands in the path of major urban development (see political action).

The Oak Ridges Moraine is a pair of large ridges composed of four elevated wedges. It is bounded to the west by the Niagara Escarpment, a cuesta which was critical to the formation of the moraine, and to the east by the Trent River and Rice Lake. The four wedges (Albion, Uxbridge, Pontypool and Rice Lake from west to east) formed in stages, though some synchronous formation also occurred at an early period of formation. The moraine peaks at the Uxbridge wedge, generally rising from east to west, a result of the moraine's west-to-east formation. That is, the western portion of the moraine received earlier and more frequent sedimentary deposition than the eastern portion, as the ice lobes which controlled the moraine's eastern formation slowly retreated. The Rice Lake wedge is separated from the other wedges where the Oak Ridges Moraine intersects Rice Lake.

To the north are drumlinized uplands, referred to as the Peterborough drumlin field.

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