Lake Maracaibo
Geology

Lake Maracaibo is located within the eponymous basin and is one of the oldest lakes on earth. It was formed 36 million years ago when the faults collapsed when the Andes were uplifted in the late Eocene. In the geological history, sea water and fresh water have alternated many times, and have flooded the area. At the end of the last glacial period, the sea level rose, connecting Lake Maracaibo directly with the Atlantic Ocean, and the lighter fresh water floated on the heavier salt water, causing nutrients to be deposited on the bottom of the lake, resulting in the accumulation of more than a five kilometer thick deposit of sediment on the bedrock.

In the Pliocene, the depression of today's Lake Maracaibo reached what would be practically its current form. The numerous rivers that flow into the lake have been defining its banks, especially those that form the southern delta of the lake, where the Escalante, Catatumbo and Santa Ana rivers converge.

Lake Maracaibo is located in the Maracaibo lowland in the faulted basin between the Perija Mountains and the Merida Mountains of the Eastern Cordillera Mountains in northwestern Venezuela. The lake is in the shape of a vase. It is 210 kilometers long from north to south, 121 kilometers wide from east to west, covers an area of 13,512 square kilometers, the deepest is 35 meters, the shore length is about 1000 kilometers, and the volume is about 280 cubic kilometers. The largest river entering the lake, the Catatumbo River, enters the lake from west to east, providing 57% of the water entering the lake. In addition to the influence of the prevailing wind, the lake water circulates counterclockwise. There are also the Santa Ana River, Chama River, Motatán River, Escalante River, and about fifty other rivers which drain into it.

Lake Maracaibo is deep in the south and shallow in the north. The northern half of the lake, which looks like a bottleneck, is 55 kilometers long. The southeastern edge of the lake basin with a flat bottom is steep and the northwestern edge is gentle. It is slightly salty due to the influence of tides, and the overall salinity is between 1.5 and 3.8%. The Catatumbo River forms a bird-foot-shaped delta in the southwest of the lake basin, and the surface lake water in the delta has a salinity of only 0.13%. However, the intrusion of seawater from the mouth of the lake makes the salinity of the bottom lake water higher, reaching 0.2–0.3%. The north is connected with the Gulf of Venezuela, and the spit at the mouth of the lake extends for about 26 kilometers.
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