The Hamza River (Portuguese: Rio Hamza) is an unofficial name for what seems to be a slowly flowing aquifer in Brazil and Peru, approximately 6,000 kilometres (3,700 mi) long at a depth of nearly 4 kilometres (2.5 mi). Its discovery was announced in 2011 at a meeting of the Geophysical Society in Rio de Janeiro. The unofficial name is in honour of Indian scientist Valiya Mannathal Hamza, of Brazil's National Observatory, who has undertaken research on the region for four decades. The Hamza "river" and the Amazon River form a geologically unusual instance of a twin-river system flowing at different levels of the Earth's crust.