Calderas are massive crater-like volcanic features that can cover many tens of square miles. A caldera is a volcano without a cone. These calderas form one of two ways. One way is when volcanoes erupt with terrible destruction. The emptying of the magma chamber below and destroying the original volcano results in a caldera. Another way calderas may form is over time, with a series of smaller volcanic eruptions.
Aerial view at Caldera Batur.
They are different from craters. Craters form from blasts happening outward, blowing away debris. Calderas form from the volcano sinking inward. In the Portuguese language, caldera translates to “cauldron”.
A caldera has felsic magma, which is high in silica and gas. They have explosive eruptions with pyroclastic flows.
One famous example of a caldera is North America’s Crater Lake. Around 7,000 years ago a massive volcanic peak reaching 12,000 feet in elevation was set in this location. A powerful eruption blasted the top 4,000 feet away, leaving a deep bowl-shaped caldera. Since that time, a new dome has begun to form in the center of the caldera.
The largest caldera in the United States is in Yellowstone National Park. The Yellowstone caldera is often referred to as the Yellowstone Supervolcano. It measures at about 34 by 45 miles. The last time the Yellowstone caldera erupted was about 650,000 years ago. This eruption released about 1,000 kg of debris, covering much of North America. At the same time, the lava cooled to form many of the landforms we know today.
A picture of a geyser erupting in Yellowstone Park. Geysers exist in areas of high volcanic activity.
The Yellowstone Caldera is over the Yellowstone hotspot. This causes the Caldera to still be active! That said, it’s very unlikely that it will erupt anytime soon.
The largest volcanic structure on Earth is a caldera. This caldera is now where Lake Toba is located in Indonesia. The results of this eruption are still clear to see today. About 75,000 years ago this caldera erupted to release about 2,800 kg worth of debris. This is the largest known eruption in the last 25 million years. Anthropologists suggest that this eruption caused a volcanic winter. This winter may have reduced the human population to 2,000 – 20,000 people.