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What is a Caldera?

Mary McMahon
Mary McMahon
Mary McMahon
Mary McMahon

A caldera is a volcanic structure that is caused by the collapse of the ground around a volcano. At first glance, it often looks a great deal like a volcanic crater, but the process of its formation is different from that of traditional craters, which is why a distinction is made between the two. One of the most famous calderas in the world lies beneath Crater Lake, a stunning volcanic lake in the United States. The Greek island of Santorini also boasts a notable one that forms a natural harbor.

These structures are usually associated with stratovolcanoes and basaltic shield volcanoes. They can form in several different ways. In many cases, a volcanic eruption empties magma chambers beneath the volcano, and these chambers collapse, creating a deep depression in the ground. In other instances, the caldera is created through a gradual process of subsidence triggered by slowly weakened ground. In the case of erosion calderas, the formation is caused by the weather in the region.

A caldera lies below Crater Lake in Oregon.
A caldera lies below Crater Lake in Oregon.

The largest type are known as resurgent calderas. This is caused by the widespread collapse of magma chambers that are not associated with a particular volcano or point of eruption, and they are the largest volcanic structures on Earth. The level of volcanic activity needed to produce a resurgent caldera is quite sizable, and would cause a great deal of damage.

A caldera is caused when the ground around a volcano collapses.
A caldera is caused when the ground around a volcano collapses.

Some vulcanologists prefer “volcanic collapse crater” to “caldera,” while others refer to these structures as “cauldrons.” In fact, the term comes from the Latin word for “cauldron,” reflecting the shape of a classical caldera, so both terms are entirely appropriate. Superficially, it can be difficult to tell the difference between a caldera and a crater, especially in the case of a dormant volcano. The key thing to know about craters is that they occur around volcanic vents, which makes standing in one a much more perilous proposition.

The Greek Island of Santorini's harbor is a caldera.
The Greek Island of Santorini's harbor is a caldera.

Some calderas are so large that they cannot be identified from the ground, because people do not realize that they are walking or living in them. In these instances, satellite photographs revealed the existence of the caldera, much to the surprise of people who had settled in these regions. Others on the ocean floor have been identified with sonar technology which has been used to determine the depth of the ocean for the purpose of making relief maps.

Frequently Asked Questions

What exactly is a caldera?

The eruption of a volcano will usually cause magma chambers to collapse.
The eruption of a volcano will usually cause magma chambers to collapse.

A caldera is a large depression formed when a volcano erupts and collapses. Following a massive eruption, the emptied magma chamber can no longer support the weight of the volcanic structure above it, leading to an inward collapse, creating a large, often circular, basin-like feature that can span several kilometers in diameter.

How does a caldera differ from a crater?

While both calderas and craters are depressions, they differ in size and formation. A crater is a smaller, circular depression typically formed by the explosive ejection of rock during a volcanic eruption. In contrast, a caldera is much larger, often exceeding a kilometer in diameter, and forms due to the collapse of a volcano's summit or the emptying of its magma chamber.

Can calderas form only through volcanic activity?

Yes, calderas are specifically associated with volcanic processes. They are the result of catastrophic eruptions that deplete a volcano's magma chamber, causing the overlying land to collapse. This geological feature is not created by other processes such as meteorite impacts or sinkhole formations, which can create similar but distinct landforms.

What are some notable examples of calderas around the world?

Notable calderas include the Yellowstone Caldera in the United States, known for its geothermal features and supervolcano status. The Crater Lake in Oregon is another example, formed about 7,700 years ago. The Santorini caldera in Greece is famous for its stunning views and association with the Minoan eruption around 1600 BCE.

Are calderas considered dangerous?

Calderas can be dangerous due to their association with powerful volcanic eruptions. However, not all calderas are active. Those that are, like the Yellowstone Caldera, are closely monitored for signs of unrest. The potential for future eruptions makes understanding and respecting caldera dynamics crucial for nearby communities and authorities.

Can life thrive in a caldera environment?

Life can indeed thrive in caldera environments. These areas often host unique ecosystems due to their geothermal activity, which can create hot springs and geysers. For instance, the Yellowstone Caldera supports a rich biodiversity, including its own subspecies of cutthroat trout, and is a habitat for a variety of wildlife such as bears, wolves, and bison.

Mary McMahon
Mary McMahon

Ever since she began contributing to the site several years ago, Mary has embraced the exciting challenge of being a AllThingsNature researcher and writer. Mary has a liberal arts degree from Goddard College and spends her free time reading, cooking, and exploring the great outdoors.

Learn more...
Mary McMahon
Mary McMahon

Ever since she began contributing to the site several years ago, Mary has embraced the exciting challenge of being a AllThingsNature researcher and writer. Mary has a liberal arts degree from Goddard College and spends her free time reading, cooking, and exploring the great outdoors.

Learn more...

Discussion Comments

anon128282

@anon89310: Then look it up in a dictionary! This article was extremely helpful, and i recommend it to anyone!

anon89310

I think this is too long, i just want a simple definition. i am 12 and my final is tomorrow. i don't have time to read all this!

Amphibious54

@Glashouse - The Yellowstone Caldera actually engulfs most of Yellowstone National Park. The caldera is some 40 or so miles across, and it has been swelling in recent years. The caldera actually sits above a magma chamber that supplies the Yellowstone Super Volcano. Scientists speculate that this chamber has been filling with magma again (no need to panic though, because calderas often go through normal cycles of swelling). So to answer your question, calderas can be found on active, inactive, and dormant volcanoes. As for whether or not Yellowstone is still active, I would have to say it is dormant. A volcano this size does not erupt as frequently as smaller volcanoes, but there has been seismic and geothermal activity at Yellowstone for some time. The last minor eruption at Yellowstone occurred well over 50,000 years ago. The last major eruption, the one that formed the Yellowstone Caldera, took place over 600,000 years ago.

Glasshouse

If a volcanic crater is a more dangerous place to be than a caldera, does that mean that calderas form when volcanoes become inactive? I live in Wyoming and I always hear people referencing the Yellowstone Caldera. I went to the park a few years back, but I never knew there was a volcano there. I was wondering where this volcano is, and if it is still active?

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    • A caldera lies below Crater Lake in Oregon.
      By: Chris Boswell
      A caldera lies below Crater Lake in Oregon.
    • A caldera is caused when the ground around a volcano collapses.
      By: Byelikova Oksana
      A caldera is caused when the ground around a volcano collapses.
    • The Greek Island of Santorini's harbor is a caldera.
      By: scasti11
      The Greek Island of Santorini's harbor is a caldera.
    • The eruption of a volcano will usually cause magma chambers to collapse.
      By: kmiragaya
      The eruption of a volcano will usually cause magma chambers to collapse.