Yellowstone
Formation of a Supervolcano Tucked away in the very northeastern corner of Wyoming, and spilling out into Montana and Idaho is an area of outstanding natural beauty, beloved by tourists and natives alike. So beloved, in fact, that in 1872, President Ulysses S Grant declared it to be the first national park in the US and the second national Park on earth. We are, of course, talking of Yellowstone National Park. Scratch beneath the surface and you’ll find the Yellowstone hotspot, a plume of molten rock rising from deep within the Earth’s mantle. Interestingly, tectonic activity is causing the North America plate to slide over the magma chamber whilst the chamber itself stays put in relation to the center of the earth. As it does so, the magma chamber grows….and grows. Very occasionally, but ominously consistently, the magma chamber can grow no more and must release pressure in a violent eruption, the likes of which has not happened in the entire existence of human memory. The Yellowstone volcanic field has experienced three major eruptions in the past 2.1 million years: The Huckleberry Ridge Eruption (2.1 Million Years Ago) The first and largest of Yellowstone’s three major eruptions, known as the Huckleberry Ridge eruption, occurred approximately 2.1 million years ago. This eruption was truly colossal, ejecting an estimated 2,450 cubic kilometers (588 cubic miles) of volcanic material. To put this into perspective, Mount St. Helens ejected just 0.25 kilometres in its eruption of 1980. The Huckleberry Ridge eruption ejected 6000 times that amount of hot magma, ash and rock high up into the atmosphere. If you were around 2.1 million years ago, the first thing you’re going to want to do is stand back. The caldera alone was 100km across. But don’t worry – even from many hundreds of kilometers away, you would be able to observe the 50km high plume of ejecta. It was colossal. The ash and gases released into the atmosphere would have had profound climatic effects, likely killing every living organism within many hundreds of miles and causing a global volcanic winter for anything that survived. This period of global cooling would have drastically affected plant and animal life, leading to significant ecological disruptions. The Huckleberry Ridge eruption created the Huckleberry Ridge Tuff, a widespread deposit of ash and pumice that can be seen in the geological record seeing the world. The eruption’s sheer volume caused the ground above the magma chamber to collapse, forming the massive caldera, one of the largest calderas on Earth. The Mesa Falls Eruption (1.3 Million Years Ago) The second major eruption, known as the Mesa Falls eruption, took place around 1.3 million years ago. While smaller than the Huckleberry Ridge eruption, it was still a significant event, ejecting approximately 280 cubic kilometers (67 cubic miles) of volcanic material. The Mesa Falls eruption produced the Mesa Falls Tuff, another extensive deposit of ash and pumice. The eruption formed the Henry’s Fork Caldera, located in the Island Park region of Idaho, just west of the Yellowstone National Park boundary. This caldera measures approximately 45 kilometers (28 miles) in diameter. The climatic impact of the Mesa Falls eruption would have been less severe than that of the Huckleberry Ridge eruption, but it still would have caused significant environmental changes. The release of ash and gases into the atmosphere would have led to a short-term period of global cooling and disruptions in weather patterns. The Mesa Falls eruption highlights the cyclical nature of volcanic activity at Yellowstone. By studying the intervals between these major eruptions, geologists can better understand the behavior of the Yellowstone supervolcano and its potential future activity. The Lava Creek Eruption (640,000 Years Ago) The third and most recent major eruption, known as the Lava Creek eruption, occurred approximately 640,000 years ago. This eruption was responsible for creating the current Yellowstone Caldera, a prominent feature of the national park today. The Lava Creek eruption ejected around 1,000 cubic kilometers (240 cubic miles) of volcanic material. The Lava Creek eruption produced the Lava Creek Tuff, yet another widespread deposit of ash and pumice that blanketed much of North America. The collapse of the magma chamber following the eruption formed the Yellowstone Caldera, which measures approximately 70 kilometers (43 miles) in diameter. The climatic effects of the Lava Creek eruption would have been significant, with the release of ash and gases causing short-term cooling and disruptions to ecosystems. However, life gradually recovered, and the Yellowstone region has since been shaped by ongoing geothermal activity. The Lava Creek eruption provides a more recent example of a supereruption and its effects. The current geothermal features of Yellowstone, including world famous geysers, hot springs, and fumaroles, are a direct result of the heat and activity remaining from this last major eruption. These eruptions have shaped the landscape of the region, creating extensive lava flows, ash deposits, and the characteristic caldera. How to spot a Supervolcano The Yellowstone Supervolcano was identified through a combination of geological, geophysical, and geochemical studies. Early explorers and geologists noted the region’s extensive geothermal activity, but were unable to locate the caldera. but it wasn’t until the mid-20th century that the true nature of Yellowstone’s volcanic system was understood. Advances in seismic imaging, satellite technology, and other scientific tools showed that the entire central portion of the park was caldera. The Yellowstone Caldera The caldera at Yellowstone was almost entirely formed by the final eruption, the Lava Creek eruption. Unlike most volcanoes, with their recognisable conical shape and caldera sat atop, The Yellowstone Caldera is massive. It’s simply too big to see in a single vista with the naked eye. The volcanic depression was formed during the final eruption not so much by the accumulation of materials around a central caldera as most volcanoes form, but rather by the literal collapse of earth as the staggering amount of materials were blown out into the atmosphere. The caldera, measuring approximately 55 by 72 kilometers (34 by 45 miles) doesn’t really project up into