The Amazon, the world’s largest river, used to be a large wetland connected to the Caribbean until 14 million years ago, when the uplift of the Andes mountains caused an enormous change in continental drainage, blocking westward flow, creating the river as we know it today formed, flowing into the Atlantic Ocean.
According to Grace Shephard, Professor Dietmar Müller and a team of international colleagues who have reported their discovery in the journal Nature Geoscience, progressive continental tilting established a gently inclined drainage surface that forced water from a giant catchment to flow to the east, starting at about 14 million years ago.
Along the edge of the Pacific, ocean crust had plunged into the sticky rocks of the Earth’s mantle for eons. “This process created a massive crustal graveyard deep inside the Earth, where huge masses of old, cold tectonic slabs are sinking, drawing the surface down,” Muller said.
“As South America made its way westward over this ‘slab burial ground’, the continent’s northeast was progressively drawn down by several hundred meters, creating something akin to the world’s largest water slide.”
Their work is significant in that it shows that the interplay between shifting continents and the slow convection of mantle rocks underneath, akin to croutons floating on a thick pumpkin soup, can fundamentally change the Earth’s surface topography, river systems, and ultimately ecosystems through geological time.
Casey Kazan via University of Sydney