In class today, Professor Pillar presented some information on calderas. These wide volcanoes sparked my interest, so I decided to find out more about them.
Calderas can cause a significant amount of damage. “They can have the power of many nuclear explosions. They may bring famine, pestilence, tsunamis, plaques, great pyroclastic flows, darkness for many days or months, global climatic change, and, possibly, very pretty sunsets.” Calderas are formed when a previous volcano erupts rapidly, and the lava is expelled so quickly that the magma chamber is emptied. The land beneath the volcano then collapses, leaving a cauldron-like depression known as a caldera.
Calderas usually have a high silica content, which means their lava has a high viscosity. High viscosity lava, because of its thickness, does not allow gases to escape from the volcano easily. This creates a very violent eruption, and ash is spread across a very wide diameter of land. If volcanic activity continues after the caldera has erupted, a volcanic dome may form. This threat of an extremely violent eruption and large amounts of ash are what make the Yellowstone caldera so ominous.
Although some calderas are extremely violent and dangerous, others are much less threatening. Calderas such as Kilauea are basalt-based, which lowers their viscosity, creating much less dense lava. Instead of violent eruptions, these calderas only produce large lava flows that are not normally very threatening.
One famous caldera can be found in Yellowstone. This caldera is about 35 miles by 45 miles, making it one of the largest calderas in the world. It was named the Yellowstone Supervolcano. Because Yellowstone lies on a hotspot, it is the home of much volcanic activity. Some hazards that can be caused by these volcanoes include earthquakes, changes in weather patterns, and toxic gases.
Although the Yellowstone Caldera has not erupted in about 70,000 years, hydrothermic and seismic activities have been measures, and the caldera seems restless. This huge caldera is responsible for Yellowstone’s many geysers and hot springs. Between 1923 and 1984, part of the crust beneath the caldera moved as much as 86 centimeters. Some scientists claim that this may be only due to the fact that Yellowstone is a very seismically active area, and that the magma chambers may be moving.
Another very well-known caldera, Kilauea, is located in Hawaii. At one time, it was believed that Kilauea sprouted from another larger volcano’s magma chamber, but research shows that Kilauea is in fact has its own magma chamber. This volcano covers 552 square miles. Some say this is the world’s most active volcano. It’s oldest rocks are about 23,000 years old, and it has erupted 61 times. Its name, Kilauea, means “spewing” or “much spreading” in Hawaiian. Hawaiians have many legends about Kilauea, and one of them is that the volcano goddess lives there.