Bruneau-Jarbidge caldera facts for kids
The Bruneau-Jarbidge caldera is a huge ancient volcano in southwest Idaho. It's sometimes called a supervolcano. This giant volcano erupted a long time ago, between 10 and 12 million years ago, during a period called the Miocene era.
When it erupted, it created a massive event called the Bruneau-Jarbidge event. This event spread a thick layer of volcanic ash far and wide. Animals living near the volcano were affected by hot, fast-moving flows of ash and gas. Animals much farther away, like those at Ashfall Fossil Beds in Nebraska (about 1,000 miles away!), also suffered. They were covered by up to two meters of ash, which led to slow suffocation and starvation. At the time of the eruption, the Bruneau-Jarbidge caldera was located over the Yellowstone hotspot.
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What is the Bruneau-Jarbidge Caldera?
A caldera is a large, bowl-shaped hollow that forms when the ground collapses after a volcanic eruption. This happens when a volcano erupts so much magma (molten rock) that the empty space beneath can no longer support the ground above it. The Bruneau-Jarbidge caldera is one of the largest calderas ever found.
How Big Was the Eruption?
The Bruneau-Jarbidge eruption was incredibly powerful. It sent huge amounts of ash high into the atmosphere. Scientists can tell how big it was by studying the ash layers it left behind. This ash spread across a huge area of central North America.
How Do Scientists Study Ancient Eruptions?
Scientists can identify ash from the Bruneau-Jarbidge volcano because it has a special chemical makeup. The tiny crystals and glass pieces in the ash also have a unique size and shape. This helps them tell it apart from ash from other volcanoes that erupted millions of years ago. They found this specific ash as far away as Ashfall Fossil Beds in Nebraska, about 1,600 kilometers (1,000 miles) to the east. Strong winds, called westerlies, carried the ash across the Great Plains.
Connection to the Yellowstone Hotspot
The Bruneau-Jarbidge caldera is part of a chain of ancient volcanoes. This chain was formed as the North American continent slowly moved over a very hot spot deep inside the Earth. This hot spot is now under Yellowstone National Park. As the continent moved, the hot spot created new volcanoes over millions of years. The Bruneau-Jarbidge caldera is an older "scar" left by this moving hotspot.
What is a Hotspot?
A hotspot is a place deep within the Earth where magma is unusually hot. This hot magma rises to the surface, melting the rock above it and causing volcanoes to form. Unlike volcanoes at the edges of tectonic plates, hotspot volcanoes can form in the middle of a plate.
How Does the Hotspot Move?
The hotspot itself doesn't move much. Instead, the Earth's tectonic plates move slowly over the hotspot. Imagine holding a candle flame (the hotspot) steady while you slowly move a piece of paper (the continent) over it. The flame will burn a line of holes in the paper. In the same way, the Yellowstone hotspot has created a trail of ancient volcanoes, with the Bruneau-Jarbidge caldera being one of them.
