Eruption
and Erosion
Science tells us a different story of the Iguazú Falls. The falls started to form about 130 million years ago when the supercontinent Gondwana broke apart. South America separated from Africa. This triggered one of the largest volcanic events in Earth’s history.
At the time, the area where the Iguazú Falls is located was a giant desert. Lava poured from volcanoes and other openings in Earth’s crust. It covered the desert. Then the lava cooled and hardened. It built up a plateau made of three, massive flat layers of basalt rock.
Waterfalls are formed as a river flows from hard rock to soft rock.
The river erodes the soft rock at a faster rate. It forms a step in the river bed.
The hard rock that is left creates a hard ledge. The river falls over the ledge.
The Iguazú River empties into the Paraná River where the borders of Brazil, Argentina, and Paraguay meet. This area is known as the Triple Frontier.
But Earth’s plates kept moving. The layers were lifted into a high plateau. Faults, or cracks, appeared in them. Water started to run down the faults and eroded, or wore away, the land. The mighty Paraná riverbed formed. Much later, the Iguazú River appeared and started to feed into it.
The falls started to form at the site where these two rivers meet. But today, they are about 23 kilometers (14 miles) upstream. Erosion, once again, gets the credit. As water fell into the Paraná River from the Iguazú’s plateau, it weathered away the layers of rock on the bottom. The upper layers had nothing to support them, so
they crumbled.
Today, the layers of Iguazú Falls look like a giant staircase. And a long, narrow canyon with scores of rocky islands leads the way to the Paraná River. Erosion continues, and the canyon gets about 3 millimeters
(0.1 inches) longer each year.
Brazil
Argentina
Paraná
Iguazú
Paraguay
Into the Rainforest
As amazing as the waterfalls are, the water is just part of the beauty that surrounds Iguazú Falls. They exist in the subtropical Atlantic Forest, one of the most biodiverse ecosystems in South America. It is home to more than 2,000 plant species,
68 mammals, 422 birds, more than
40 reptiles, 18 amphibians, and 250 types of butterflies. Many of the plants and animals that live here aren’t found anywhere else in the world.
black capuchin monkey
toucan
Beware of the coatis! They can easily bite your hand when they try to grab your food.
As I walked through the rainforest, I saw tall palm trees and even taller laurels and rosewoods. Papaya fruit hung from small trees under the umbrellas of huge leaves.
Flashes of blue fluttered through the air. Your eye had to be quick to spot these blue morpho butterflies. I also caught a glimpse of a toucan in flight. I saw capybaras sunning themselves on the riverbank. I also got a good view of a young caiman resting in shallow water. Raccoon-like coatis seemed to be everywhere! I kept an eye out for tapirs, monkeys, giant anteaters, or jaguars. Those animals live here, too.