Lake Okeechobee Valley and the Everglades. The trough is underlain by clay deposits that compacted more than the limestone and sand deposits did along both coasts of peninsular Florida. Until about 6,000 years ago, the trough was dry land. As the sea level rose, the water table in Florida also rose and rainfall increased. From 6,000 to 4,000 years ago, wetlands formed building up peat deposits. Eventually the water flow into the area created a lake, drowning the wetlands. Along what is now the southern edge of the lake, the wetlands built up the layers of peat rapidly enough (reaching thick) to
Geography of Florida Florida's Apalachicola River. (Since Woodruff Dam was built, this point has been under Lake Seminole.) The border with Georgia continues north through the lake for a short distance up the former thalweg of the Chattahoochee, then with Alabama runs due west along 31°N to the Perdido River, then south along its thalweg to the Gulf via Perdido Bay. Much of the state is at or near sea level.Florida is also 65,755 square miles. The climate of Florida is tempered by the fact that no part of the state is very distant from the ocean. North of Lake Okeechobee, the prevalent