Inside the Yellowstone supervolcano eruption that would 'instantly' kill 90,000 people

The most recent supervolcanic eruption on Earth occurred approximately 27,000 years ago, during the Stone Age, when early humans were still fashioning tools and decorating cave walls. This colossal event, known as the Oruanui eruption, originated from in New Zealand's North Island.

The eruption blanketed large areas in volcanic ash, up to 7 inches (18 cm) deep in some regions, with deposits believed to have spread as far as 620 miles (1,000 kilometers) away.

What sets supervolcanoes apart from typical volcanoes is the scale of their eruptions. These are classified as magnitude 8 on the (VEI), which means they eject over 1,000 cubic kilometers (about 240 cubic miles) of volcanic material in a single event.

One of the most closely studied and potentially dangerous supervolcanoes today is located in the United States: the Yellowstone Caldera in Wyoming. Although it lies beneath the serene and scenic , this sleeping giant harbours a volcanic system capable of continent-altering devastation.

According to a documentary on Yellowstone, while the volcano has remained dormant for roughly 640,000 years, scientists continue to monitor it for signs of renewed activity. The region experiences periodic releases of underground pressure through its famous geysers and hot springs.

If pressure were to build up significantly, it could melt the rock beneath the surface and form a volatile mix of magma, gases, and rock. This mixture could eventually create a bulging dome on the surface, and in a worst-case scenario, erupt with cataclysmic force.

Should such an eruption occur, the documentary noted that the initial explosion could "immediately" kill up to 90,000 people. The devastation would not stop there, as lava flows and pyroclastic materials could cover an area stretching over 1,000 miles (1,600 kilometers), engulfing neighboring states such as Montana and Idaho. Emergency response efforts would be severely hindered by the dangerous terrain and widespread destruction.

The eruption would also hurl vast amounts of ash into the atmosphere, disrupting air travel across a massive radius, similar to the 2010 eruption of , but on a much larger scale.

The ash cloud could circle the globe and contribute to a phenomenon known as a "volcanic winter." This occurs when sulfur dioxide from the eruption forms a reflective aerosol layer in the upper atmosphere, blocking sunlight and drastically cooling the planet.

Temperatures could drop by as much as 10°C (18°F) worldwide. Such a dramatic cooling event could disrupt global agriculture, leading to widespread crop failures and food shortages, especially in regions already vulnerable to famine.

Despite the catastrophic potential, the likelihood of a Yellowstone supereruption remains very low. The (USGS) estimates the annual probability of such an event at roughly 0.00014%-about 1 in 730,000.

USGS scientists emphasise that "there is no evidence that a catastrophic eruption at Yellowstone is imminent" and consider it unlikely to happen within the next few centuries.

They also note that "scientists have found no indication of an imminent smaller eruption of lava."