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The Oak Ridges Moraine is a geological landform that runs east-west across south central Ontario, Canada. It developed about 12,000 years ago, during the Wisconsin glaciation in North America. A complex ridge of sedimentary material, the moraine is known to have partially developed under water. The Niagara Escarpment played a key role in forming the moraine in that it acted as a dam for glacial meltwater trapped between it and two ice lobes. In order to understand the process by which the moraine formed, it is necessary to understand the physical geography in which it currently exists (that is, its physiography), and the layers of sediments found within it (the stratigraphy of the moraine). ==Regional physiography== The Oak Ridges Moraine consists of four elevated, wedge-shaped structures; from west to east, they are: * The Albion Hills wedge, * the Uxbridge wedge, * the Pontypool wedge, and * the Rice Lake wedge. These wedges are separated by narrow east to west ridges, and formed via sedimentation. The hummocky terrain, small elevated plains and narrow ridges suggest that its formation is of glacial origin. The moraine is nearly bisected in the east; the Rice Lake wedge is isolated from the three western wedges since the moraine is absent directly south of Rice Lake. Four primary geophysical structures are intimately tied to the formative processes of the Oak Ridges Moraine: * the Niagara Escarpment to the west * drumlinized uplands in the north, with extensions south of the Oak Ridges Moraine * wide, flat-floored valleys, primarily in the north * low-relief plains in the south. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Origin of the Oak Ridges Moraine」の詳細全文を読む スポンサード リンク
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