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〕 | traversed = Interstate 80, Pennsylvania Route 611, Delaware–Lackawanna Railroad | location = New Jersey/Pennsylvania, United States | range = Blue Mountains/Kittatinny Ridge | coordinates = 〔 | topo = Portland, Stroudsburg }} The Delaware Water Gap is a water gap on the border of the U.S. states of New Jersey and Pennsylvania where the Delaware River cuts through a large ridge of the Appalachian Mountains. The gap constitutes the southern portion of the Delaware Water Gap National Recreation Area, which is used primarily for recreational purposes, such as rafting, canoeing, swimming, fishing, hiking, and rock climbing. ==Geology== A water gap is a geological feature where a river cuts through a mountain ridge. The Delaware Water Gap began to form 500 million years ago when quartz pebbles were deposited in a shallow sea from mountains in the area. The Martinsburg Shale on the eastern side of the ridge was uplifted 450 million years ago when a chain of volcanic islands collided with proto-North America. These islands slid over the North American plate, and deposited rock on top of plate, forming the Highlands and Kittatinny Valley. Then, about 400 million years ago, a small, narrow continent collided with proto-North America. Pressure from the collision uplifted the Silurian Shawangunk Conglomerate. The pressure created heat, melted the quartzite, which allowed it to bend, the quartz pebbles, and conglomerate. This layer was then uplifted, which then cracked during the uplift. As uplifting occurred over thousands of years, the Delaware River slowly cut its path down through the shattered and cracked quartzite. If the quartzite had not been cracked, the river would not have been able to cut its path through the mountain forming the gap. Millions of years of rain, ice, snow, and wind erosion shaped the area. The Wisconsin glaciation, which occurred between 21,000 B.C. to 13,000 B.C., covered the entire Kittatinny Ridge and ended near Belvidere. When the glaciers retreated, the gap assumed its present form. The mountain consists of Silurian Shawangunk conglomerate. This is gray quartzite, which makes the mountain highly resistant to weathering. The Silurian High Fall formation of sandstone is on the western side of the gap near the base. The eastern side of the Gap has the Ordovician Martinsburg shale. Sedimentary rock is along the river. The Bloomsburg Red Beds, a red shale, are at the Gap under Dunsfield Creek. The Delaware Water Gap is about 300 meters across at river level and 1,400 meters wide at the top. The river through the gap is 283 feet above sea level. The ridge of the Appalachians that the Delaware crosses is called the Blue Mountains in Pennsylvania and the Kittatinny Ridge in New Jersey. This is the first major ridge of the Appalachian mountains. The New Jersey mountain is Mount Tammany, named after the Native American Chief Tamanend. The Pennsylvania mountain is Mount Minsi, named after the Native American tribe of the area. The summit of Tammany is above sea level. 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「Delaware Water Gap」の詳細全文を読む スポンサード リンク
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