The Great Roar of the Amazon
Near the mouth of the Amazon, a deep roar is heard half an hour before a wall of water comes racing upriver.
What was reported
Where the Amazon and nearby rivers meet the Atlantic, people hear a deep roar coming from the sea, around 30 minutes before a wave several metres high surges upriver against the current, tearing at trees and banks. Local people call it the pororoca, from a Tupi word for a great roar.
Folk stories explained it as the work of river creatures. Today, surfers come to ride the wave for many kilometres.
Explanations offered
It is a tidal bore. Around the new and full moons, especially near the spring and autumn equinoxes, the strongest tides push into the shallow river mouths and build into a single wave that travels upstream. The roar is the sound of the wave breaking ahead of its arrival.
- When
- Twice a year, at the highest tides
- Where
- Mouth of the Amazon, Amapá and Pará, Brazil
- Witnesses
- River communities and surfers
- Status
- Explained
Famous cases are real, widely reported events. Each file sets out what witnesses said and the explanations that have been offered, without taking a side.