Geological Formation of the Iguassu Falls
Originally, the seven continents were joined together in a supercontinent called Pangea. Two hundred million years ago, the first rupture in this supercontinent took place between Africa and South America. One hundred million years ago, eruptions of basaltic lava broke through chasms in the Earth´s crust, forming spillways several kilometers high in layers several meters thick. The Iguassu Falls are formed by three of these spillways mostly covered by water; a larger one, between 141 and 180 meters high, a smaller one, between 116 and 141 meters high, and an even smaller one, less than 116 meters high. The Falls are formed in three steps by these spillways; one smaller fall and two higher ones. Horizontal and vertical movement of the continental plates created vertical cracks in the basalt rock. These big cracks are called faults. A system of these faults runs through the Iguassu region. The principal channel of the Iguassu River runs through one of the faults where erosion has been more intense. Several other transversal faults form a series of falls on the Argentinean side. The erosion continues along the principal channel, but the very resistance of the basalt rock makes the changes almost imperceptible.

Basalt rock
Basalt is a volcanic rock formed by the melting of pre-existent material deep in the lithosphere (magma). When reaching the surface, it spreads and becomes lava. Composed almost entirely of dark, fine-grained silicate minerals, chiefly plagioclase feldspar and pyroxene, and magnetite, basalt is usually dark gray in color, and often has a vesicular texture, preserving vestiges of bubbles produced by expanding steam as lava cools and solidifies. While drilling in Brazil, Petrobras, the Brazilian Petroleum Company, has found basalt layers of more than 1,500 meters (5,000 feet). In the Iguassu Falls region, there are approximately 1,000 meters (3,250 feet) of basalt. According to geologists from the Itaipu Dam, the Iguassu region has between 8 to 10 layers of basaltic rock. Some literature says in some areas of Brazil there are 40 to 50 layers of basalt lava.

The Guarani Aquifer

Where is the sixth largest under ground reservoir of water in the world?

It is located under the Iguassu Falls region. The Guarani Aquifer is the largest trans frontier underground fresh-water reservoir in the world. It extends from the Parana Sedimentary Basin located within the countries of Brazil, Paraguay and Uruguay to the Chaco Basin located principally in Argentina. It is located in east-central South America between 12 and 35 degrees latitude south and 47 and 65 degrees longitude west. The Guarani Aquifer has a preliminarily defined total extension of approximately 1.2 million square km. The Guarani Aquifer is made up of many arenaceous layers that were deposited in the Parana Sedimentary Basin during the Mesozoic Era (during the Triassic, Jurassic and Cretaceous Periods) between 200 and 132 million years ago. At the moment the aquifer is in a dangerous situation.

Warning
The use of deep artesian wells it is consuming all the under groundwater very quickly. Anyone can get a license to drill and get out the precious water.