Text Box: Piedmont Plateau Introduction | Physical Features | Resources                                                       The Piedmont Plateau extends approximately 1,000 miles from southeastern New York to east-central Alabama.  A portion in northern New Jersey, and the northern end of the province, which extends only a few miles into New York, are in some places just 10 miles wide; it is widest–about 150 miles–near the border of Virginia and North Carolina and in central Georgia.  Elevations are highest in the southern part, achieving a maximum in Georgia, and decrease somewhat regularly northward,  the lowest elevation occurring in New Jersey.  The Fall Line, which is the contact between the Piedmont Plateau and the Atlantic-Gulf Coastal Plain provinces, forms nearly the entire eastern border of the province.  Only the very northern portion of the Piedmont Plateau that extends northward of New York City along the Hudson River does not have the Fall Line as its eastern boundary.  The western side of the province borders on three provinces–New England, Ridge and Valley and the Blue Ridge.  The most prominent part of this western border is the Blue Ridge Escarpment in Virginia and North Carolina, which is very straight in some sections and rises to 2,500 feet above its immediate surroundings in North Carolina.  The province is often referred to as the foothills of the Appalachian Mountains (the word piedmont means foot of mountains); in Georgia the province rises from an elevation of 500 feet at the Fall Line to almost 2,000 feet at the inner boundary of the province.  As such, this province  is considered one of the five Appalachian provinces–along with the Blue Ridge, New England, Ridge and Valley, and Appalachian Plateaus provinces.    Structure and Rock Types The Piedmont Plateau  is a region of mostly rolling or undulating topography punctuated with ridges, very prominent monadnocks, and valleys, some as deep as 300 feet.  This undulating topography has resulted from three processes:  1) minor uplift that commenced after the last major orogeny (Allegheny) that formed the Appalachians; 2) isostatic upwarping; and 3) renewed river erosion, apparently associated with continuing plate movement and widening of the Atlantic Ocean. Metamorphic rocks are the most common, covering more than half of the province.  Most abundant are gneisses and schists, but also present are marble, quartzite and slate.  The Carolina Slate Belt, which  comprises about one-fifth of the province, extends about 400 miles from southern Virginia across the central portion of the Carolinas to central Georgia along the eastern part of the province.  The slate here is slightly less resistant to weathering than surrounding rocks and thus this belt now occurs as a relatively low area within the province.  About one-fifth of the Piedmont Plateau is granite (or granite gneiss).  Several prominent monadnocks are composed of granite.  A few intrusions, some now exposed at the surface, consist mostly of diabase and gabbro.  Most rocks in the province have now been determined to be of early Paleozoic age, in contrast to earlier estimates of Precambrian age.  Much of the surface exhibits severe weathering, and the term saprolite is used for the residual, very weathered rock that mantles much of the province.  Saprolite is most common in the southeastern part of the country, but also occurs in the Midwest, including Wisconsin and Minnesota.  This material varies greatly in thickness but generally increases southward within the Piedmont Plateau.  Continental glaciers, which covered only a very small area of the northern portion of the province, produced minor surface changes and slightly altered the character of the saprolite in the north.    Piedmont Plateau Introduction | Physical Features | Resources