world nature 2020

                         It is best not to envision groundwater as underground lakes and streams (which only occasionally exist in caves). Instead, think of groundwater slowly seeping from one minuscule pore in the rock to another. Have you ever been to the beach and dug a hole, only to have it filled with water from the base? If so, you had reached the water table, the boundary between the unsaturated and saturated zones. Rocks and soil just beneath the land’s surface are part of the unsaturated zone, and pore spaces in them are filled with air. Once the water table is reached, then rocks and soil pore spaces are filled with water, in the saturated zone.               The water table is said to mimic topography, in that it generally lies near the surface of the ground (often tens of feet below the surface, though this can vary greatly with location). The water table rises with hills...

Forest Waterfalls  basalts is most intense in two nearly (but not quite) parallel directions, and the river has cut a zigzag path working upstream, first along one direction of weakness, then the other. Presently it appears to be just at the point where it will take another sharp bend. Other examples of waterfalls produced by uplift of plateaus include Angel Falls in Venezuela—the highest in the world at 977 meters (3,212 feet)—and the collection of smaller waterfalls along the "fall line" at the eastern edge of the Appalachian Mountains. Situated on the border of Brazil, Argentina, and Paraguay, Iguazu Falls consists of 275 cascades spread across nearly 3.3 kilometers (2 miles). With an average (nonflood) discharge of 1,700 cubic meters per second (60,000 cubic feet per second), these falls are among the most powerful in the world. Situated on the border of Brazil, Argentina, and Paraguay, Iguazu Falls consists of 275 cascades spread across nearly 3.3 kilometers (2 miles)...