What Happened On March 18th?

On March 18th of 1971, the coast of the Peruvian Andes was shattered. A monstrous wave, a megatsunami, exceeding 100 feet (30 meters) in height, roared out of the turquoise waters of Lake Yanahuani. Starting with a colossal rock avalanche which fell 1,300 feet from Mount Huascarán, a massive wave was triggered and surged towards the mining town of Yungay, just over a mile away. The consequences were devastating as Yungay was utterly obliterated, leaving behind an estimated 500 to 700 victims.

Similar to how the Sanriku tsunami began 38 years prior, a powerful earthquake (estimated between 7.0 and 7.7 on the Richter scale) destabilized a massive section of Mount Huascarán’s slope. Millions of tons of rock plunged into the narrow valley where Lake Yanahuani resided. The impact displaced an immense volume of water with force, creating a wave unlike any other witnessed in the region.

Yungay’s location sealed its fate. Situated directly in the path of the potential wave, the town in between the valley acted as a natural funnel. This amplified the force of the water as it surged towards its target.

Tragically, this disaster was not entirely unforeseen. Geologists had previously warned of the precarious situation surrounding Lake Yanahuani and the risk of landslides triggering massive waves. These warnings, however, went unheeded, leaving Yungay unprepared for the impending catastrophe.

The exact timeframe between the rock avalanche and the wave striking Yungay still is a subject of debate. Estimates range from a harrowing two minutes to a slightly more forgiving ten minutes. Regardless of the exact window, it was tragically short, leaving the residents with little to no chance of escape.

Following the disaster, a new Yungay was built at a safe distance from the lake, reinsuring that something like this would never happen again.

1971 seemed to be the year of Earth tremors as the famous Sylmar earthquake occurred just a month prior. Do you think that this was just a coincidence?