BIRTH OF A RIVERTectonic plates shifted millions of years ago
BIRTH OF A RIVER
As tectonic plates shifted millions of years ago, the Andes rose, transforming South Americas drainage basins The east-flowing Amazon River that we know today took shape 10.5 million years ago. The river and its tributaries now flow through three major types of forest. In two of them, igapo and vårzea, the rivers can be divided into three types: black. clear, and white.
Acidic and low in nutrients, these waters are stained dark by decomposing plants
CLEAR WATER These rivers are low in sediments because they drain ancient shields of rock.
WHITE WATER Nutrient-rich sediments flow from the Andes. clouding these rivers.
WATER AND NUTRIENT CYCLE In all three types of forest
RAIN FOREST CIRCULATION Much of Amazonias water stays in Amazonia. Winds from the east blow moist ocean air over the forest, and plant transpiration circulates more than half the rainfall back into the atmosphere—a cycle that repeats four or five times, moving from the Atlantic to the Andes. A shrinking forest threatens to interrupt this cycle.