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The Valparaiso Moraine is a terminal moraine that forms an immense U around the Lake Michigan basin in North America. It is a band of high, hilly terrain made up of glacial till and sand. It begins near the border of Wisconsin and Illinois and extends south through Lake, McHenry, Cook, DuPage and Will counties in Illinois, and then turns southeast, entering Indiana. From this point, the moraine curves northeast through Lake, Porter, and LaPorte counties of Indiana into Michigan. It continues into Michigan as far as Montcalm County. It was formed during the Crown Point Phase of the Wisconsin glaciation. At this time the glacier covering the area had grown thin, so it was restrained by the dolomite rock layers of the Lake Michigan basin. Where the glacier stopped, glacial till and sand was deposited, creating the hills of the moraine. After the Valparaiso Moraine was formed, the glacier retreated and formed the Tinley Moraine. Many towns in northwest Indiana and northeast Illinois are named after the Valparaiso Moraine or the Tinley Moraine. Also, many small creeks or rivers start in the Valparaiso Moraine. The moraine itself was named after the city of Valparaiso, Indiana, where the moraine is narrower and higher than in other places. The Valparaiso Moraine forms part of the St. Lawrence Seaway Divide, bounding the Great Lakes Basin. Water on one side of the moraine flows into Lake Michigan, through the Great Lakes, and eventually into the Atlantic Ocean via the Saint Lawrence River, while water on the other side flows into tributaries of the Mississippi River, which eventually flows into the Gulf of Mexico. ==History== The Valparaiso Moraine formed as the first major moraine of the Cary substage of the Wisconsin Glacial period (10,000-50,000 years before present).〔Hough, Jack L.; ''Geology of the Great Lakes''; University of Illinois Press, Urbana; 1958, pg 97〕 There are three minor moraines that have been identified in northeastern Illinois, the Minooka, Rockdale, and Manhattan. Within the arc created by the Valparaiso Moraine are two younger Cary substage moraines of the Tinley Moraine and the Lake Border Moraine. Younger still is the Port Huron system, which occurs in the northern portion of the Lake Michigan Basin. The Cary substage dates to around 30,000 years before present.〔 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「Valparaiso Moraine」の詳細全文を読む スポンサード リンク
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