Roughly 145 to 150 million years ago, in the late Jurassic, a warm shallow sea covered what is now northern Patagonia. Plankton bloomed and died and drifted to the bottom, layer upon layer, sealed in oxygen-starved mud where decay could not finish its work. Over geologic time, heat and pressure cooked that organic carbon into oil and gas, locked inside dense black shale and marl. The formation spreads across about 30,000 square kilometers of the Neuquén Basin and sits roughly 2,900 meters down. American geologist Charles E. Weaver gave it its formal name in 1931, though the bituminous shales had been described decades earlier. The same rock preserves the bones of the sea's old inhabitants: ichthyosaurs, marine crocodiles, and pterosaurs whose fossils still emerge from its outcrops.

Conventional wells in the Neuquén Basin had pumped since 1918, but they drew from porous rocks that the Vaca Muerta merely fed from below. The shale itself held its oil too tightly to flow. That changed in 2008, when a team at Repsol-YPF, led by Mikel Erquiaga, screened every source rock in Argentina and bet on Vaca Muerta. In July 2010 they completed the country's first shale gas well; by August 2011 the first horizontal well snaked sideways through the formation. Hydraulic fracturing did the rest, splitting the brittle rock so the trapped hydrocarbons could escape. The discovery rewired Argentina's energy future. The U.S. Energy Information Administration ranks Vaca Muerta among the largest shale resources on Earth, with roughly 16 billion barrels of recoverable oil and 308 trillion cubic feet of gas.

What followed was a stampede. Chevron, Shell, ExxonMobil, Petronas, Dow, and dozens of other firms poured billions into the steppe. Around 500 fracking wells existed in 2017; by late 2024 there were more than 1,500. The output curve is almost vertical. Production climbed from about 45,000 barrels a day in 2014 to roughly 453,000 by December 2024, and kept rising past 578,000 barrels a day in late 2025, with forecasters targeting a million by 2030. The little crossroads town of Anelo, once a dot on the map, swelled into a boomtown of trucks, man camps, and proppant sand. The World Bank and global investment banks now finance the urban planning that a fracking frontier demands.

A boom this size leaves marks on the land and the people who live on it. Each well can demand hundreds of water trucks across its lifetime, the equivalent of several Olympic pools, in a region where water is already scarce and farmers and sand miners compete for the same ground. In July 2013, protests against a sixteen-billion-dollar YPF-Chevron deal were met with heavy police force. Five years later, Mapuche communities sued Exxon, TotalEnergies, and Pan American Energy, alleging that oily fracking sludge had been dumped in illegal waste sites near Anelo. The Mapuche have lived in this part of Patagonia for centuries; the question of who bears the cost of the boom, and who reaps its rewards, remains very much open.