A reversed-J of basalt is Earth’s largest waterfall system
Iguazú Falls—or Iguaçu—span the Iguazu River between Argentina’s Misiones and Brazil’s Paraná as the world’s largest waterfall system. Guarani or Tupi y (“water”) plus ûasú (“big”) name the cataract; legend says a furious deity sliced the river when Naipí fled with lover Tarobá.
The river starts near Curitiba and runs mostly through Brazil, yet most of the drops belong to Argentina. Brazil holds over 95 percent of the basin but only a little more than a fifth of the falls, with Argentina taking nearly 80 percent. Laid out like a backward J, the edge extends 2.7 kilometres, of which about 900 metres stay dry. Álvar Núñez Cabeza de Vaca, a Spanish conquistador, was the first European to write about it, in 1541.
Three layers of basalt create two steps, 35 and 40 metres tall, belonging to the kilometre-thick Serra Geral lava sequence of the Paraná Basin. Hard bubbly basalt 8 to 10 metres thick caps each layer, and the edge wears back by roughly 1.4 to 2.1 centimetres a year. Islands break the front into 150 to 300 separate cascades depending on water level. About half the flow plunges into the Devil’s Throat, a slot 80 to 90 metres wide through which the national border runs.
Average discharge is about 1,746 cubic metres a second, sixth among the world’s waterfalls since Guaíra Falls disappeared under a reservoir in 1982, and a peak of 45,700 was measured on 9 June 2014. In 2006 drought cut it to 300 until early December. On seeing it, Eleanor Roosevelt reportedly sighed “Poor Niagara!”, since Niagara is a third shorter; Victoria Falls has a bigger single curtain, but Iguazu is wider.
Engineer André Rebouças began lobbying to protect the site in 1876, just four years after Yellowstone became the first national park. UNESCO listed Argentina’s Iguazú park in 1984 and Brazil’s Iguaçu park in 1986. Visitors come from Foz do Iguaçu, Puerto Iguazú and Paraguay’s Ciudad del Este, all with airports. Argentina bans helicopter tours to spare wildlife and runs a forest train to a kilometre-long walkway above the Devil’s Throat, while Brazil uses double-deck buses carrying 72 passengers.
Source: Iguazu Falls
