What is a Caldera?
Natural processes take time to occur and have various stages. Volcanic eruptions are one such type. During the eruption, magma present underneath comes out, the volcano explodes, and hence there is no boundary support left behind. Thus there are no sides and top of the volcano anymore as they fall inward with no support between. This depression formed due to magma eruption forms caldera. As a result, we either get steep cliffs around or lakes formation. These are huge-ranging up to 100 km in diameter. These are generally oval or circular. These have different depths, sizes, and shapes.
Caldera Volcano
The word ‘caldera’ is associated with a volcano’s huge eruption, which can eventually have different sizes, depths, and shapes. As a result of the eruption, we get a large amount of magma expelled out on the earth’s crust. This hollow cavity on the earth’s surface is sometimes referred to as a crater. However, the two are not the same. It is because a crater is formed with the subsequent collapse.
In the entire world, there have been seven known caldera volcanoes since the 1900s. The word is taken from the Spanish language, which means cooking pot. Also, this circular fracture is called a ring fault.
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Caldera Volcano Examples
A significant depression on the earth’s surface, let ground above the hollow part, is the caldera Volcano. However, different types vary according to size and shapes. Let us study some of them.
Crater-Lake Calderas
Stratovolcanoes are the most explosive types which form crater-lake calderas as a result. These are caused by Plinian eruptions, which cause colossal lava, rocks, and ash to move out of the earth. One such example is Crater Lake in the US, Oregon which is not a crater that took 7000 years to form.
Shield Volcano Calderas
Shield Volcanoes do not explode at one time. They undergo several stages and take a lot of time to pull magma out. Usually, these are characterised as lava fountaining and are less explosive. Unlike Crater-lake types, these produce nested depression on the earth’s surface. These are generally small and less than 5 km in diameter. The islands of Hawaii have good examples of shield volcano calderas.
Resurgent Calderas
These are the largest depressions running from 15 to 100 km in diameter. These are not formed by a single volcano but result from different volcanic eruptions that collapse several magma chambers. These are the most destructive types that take thousands of years to form. Toba Caldera on the Indonesian is the best example of resurgent calderas with a rough figure of 74,000 years of formation.
Some Other Caldera Volcano Examples
The Yellowstone Caldera:
It is named after its location- Yellowstone National Park, the US, where Yellowstone SuperVolcano erupted. It is a complex type that took 64,000 years to form.
Deception Island:
It is a crater-lake type located at Antarctica’s off coast with a rough figure of 10,000 years formation. It has resulted in lake formation after seawater flooded inside it.
Galápagos Islands:
This island has a series of shield volcanoes that finally resulted in the most profound hole formation.
Fernandina Island:
It has an elliptical-shaped oval depression known for the largest collapsing with magma eruption.
Crater and Caldera
Usually, people mix the two terms, Crater and Caldera, with each other. When a crater is formed, you cannot get to the largest part. Thus the change from the deepest depression to crater is irreversible.
What is a Crater in a Volcano?
When a volcano erupts, it brings different shapes and sizes. If it is a bowl-shaped depression on the earth’s surface, it is called a crater. These volcanic eruptions have steep and deep sides. As a result, a crater is formed. Craters are formed when magma or rocks from a volcano moves out and leaves behind hollow inside. There are generally Summit craters and Flank craters formed as a result of the eruption.
Difference Between Crater and Caldera
People usually confuse between a crater and caldera, but both of them are opposite. The crater is caused when volcanic eruptions cause hollow inside, letting magma out. On the other hand, the deep hollow collapses to form large craters. Craters are generally small and have small features, but giant holes are referred to as calderas.
FAQs on Calderas
1. What exactly is a caldera and how is it formed?
A caldera is a large, cauldron-like depression that forms after a volcano collapses. The formation process typically involves a massive and explosive eruption that empties the volcano's magma chamber. Without the support of the underlying magma, the ground surface and the volcanic structure above it collapse inward, creating a vast basin that is significantly larger than the original volcanic vent.
2. What is the main difference between a caldera and a volcanic crater?
The primary differences between a caldera and a crater lie in their size and formation.
- Formation: A crater is a smaller, bowl-shaped depression formed by the outward explosion of rock and other materials from a volcanic vent. In contrast, a caldera is formed by the inward collapse of a volcano following the emptying of its magma chamber.
- Size: Calderas are much larger than craters. By definition, a caldera must have a diameter of at least 1 kilometre, whereas craters are typically much smaller.
3. Can you provide some examples of famous calderas in India and around the world?
Yes, there are many notable calderas globally. Some famous examples include:
- Yellowstone Caldera, USA: One of the world's largest and most active supervolcanoes.
- Lake Toba, Indonesia: The site of a massive supervolcanic eruption about 74,000 years ago, which created the largest volcanic lake in the world.
- Crater Lake, USA: A picturesque caldera lake in Oregon that formed from the collapse of Mount Mazama.
- Dhinodhar Hills, Gujarat, India: These hills are considered the remnant of a caldera, showcasing evidence of past large-scale volcanic activity in the region.
4. What is a caldera lake and how does it form?
A caldera lake is a body of water that accumulates inside a caldera. After the caldera is formed through volcanic collapse, the large, enclosed depression begins to fill with water over thousands of years. This water primarily comes from rainwater and snowmelt, with no natural outlet until the water level rises high enough to breach the caldera rim. Crater Lake in Oregon, USA, is a perfect example of a deep and pristine caldera lake.
5. Are calderas still considered dangerous long after they form?
Yes, calderas can remain geologically active and potentially dangerous for a very long time. The magma system beneath a caldera can remain hot for thousands of years, leading to hazards such as:
- Resurgent Domes: The floor of the caldera can slowly rise as new magma re-enters the chamber below.
- Hydrothermal Activity: Geysers, hot springs, and fumaroles (gas vents) are common, indicating a hot subsurface.
- Future Eruptions: While massive caldera-forming eruptions are rare, smaller eruptions can still occur within the caldera, posing significant risks to nearby areas.
6. Why is this geographical feature named 'caldera'?
The term 'caldera' originates from the Spanish language, where it means "cauldron" or "cooking pot." The name was first applied in a geological context by the German geologist Leopold von Buch in the 19th century. He used it to describe the Las Cañadas caldera on Tenerife in the Canary Islands, as its vast, steep-walled, basin-like shape strongly resembled a large cauldron.
7. How can a large caldera-forming eruption impact the global climate?
A massive, caldera-forming eruption, often called a supereruption, can have a significant impact on global climate. During such an event, enormous quantities of volcanic ash and sulphur dioxide are ejected into the stratosphere. The sulphur dioxide mixes with water vapour to form sulphate aerosols, which can create a reflective haze that blocks incoming sunlight. This can lead to a phenomenon known as a "volcanic winter," causing a drop in global temperatures that can last for several years and disrupt ecosystems and agriculture worldwide.
