South Carolina is divided into two geographic regions by a fall line which runs through the center of the state. The fall line separates the sedimentary rocks of the Coastal Plain from the metamorphic rocks of the Piedmont and is where rivers form major rapids. The area northwest of the fall line, known as the upcountry, is part of the Piedmont Plateau. At the edge of the Piedmont are the Sandhills, which run diagonally across the center of the state from northeast to southwest. To the southeast is the low country, or The Coastal Plain. This region has a 187 mile (300 km) coastline which includes the Grand Strand - a beach stretching south from the North Carolina border for more than 100 miles (160 km). The Strand turns into the marshes of the Sea Islands, which extend into Georgia. The Blue Ridge Mountain region is in the northwestern corner of the state, and makes up just 2 percent of the state’s area. This area contains the highest point in South Carolina, Sassafras Mountain (3,560 feet/1,085 meters).
South Carolina has three large river systems. The Pee Dee in the northeast, the Santee and its tributaries in the Piedmont, and the Savannah, on the western border. The Ashley, Combahee, and Edisto are short rivers near the Sandhills that flow across the Coastal Plain. They flow through swamps, where tannic acid gives their waters a black color. South Carolina has no large natural lakes, but has several man-made lakes on the Savannah River and Santee. These were built to help create hydroelectric power. Lake Marion is the largest of these lakes, and covers 173 sq miles (48 sq km). The Coastal Plain contains hundreds oval depressions, called Carolina Bays, of different sizes. They are usually filled with water and surrounded by swamp plants. Scientists are not sure how these were formed, some geographers believe they were created by the impact of a comet or meteor.
South Carolina has a subtropical climate, with hot, humid summers and mild winters. Average temperatures in July are between the low 70s F (low 20s C) in the highland northwest, and the low 80s F (upper 20s C) in the midlands and along the coast. Average winter temperatures vary from about 38 °F (3 °C) in the mountains, to about 45 °F (7 °C) in the midlands, and around 50 °F (10 °C) on the coast. The coast has warmer temperatures because it is warmed by waters of the Gulf Stream. Most of the state receives around 50 inches (1,270 mm) of rain each year, but the mountains in the northwest often get 70 to 80 inches (1,780 to 2,030 mm). South Carolina receives around 10 tornadoes a year, and in some years hurricanes cause damage along the coast.
