Crater

You must have seen some holes or circular structures on the surface of the Moon or Mars. The same kind of holes or structures is also present on the Earth. In English, the simple meaning of this is hollow structures or dimples on the flat surface or in astronomy is a constellation.

This term has different meanings but generally, it is a bowl-shaped structure. In Ancient Greece, a large bowl was used for mixing wine which was called a crater. In Geomorphology or Physical Geography, it is a depression that can be found on the surface of any celestial object be it on the Earth or the Moon, etc. 

Most of these craters are formed because of the meteorites or volcanic activities or explosion of the bombs. Even the top of the volcano or its mouth is also known as a crater. The formation of the crater is very common and can be seen anywhere. Even in the flat painted wall, any small dimple will also be termed a crater. 

On this page, we will be talking about the concept of the crater which has different meanings as per different disciplines but majorly it is used in Geography/Geomorphology. We will learn what is a crater, define crater, features or types of craters, examples of craters on Earth along with important additional information which will solve a lot of questions about this concept. This topic will help you a lot whenever you talk about craters in Geography or Earth Sciences.

Features of Craters

Craters can have various distinct features. The floor is usually below the ground of the surrounding areas and generally either it is bowl-shaped or flat in nature. Sometimes central peaks are also seen in the craters which are formed in the central areas of the larger crater. Sometimes, the excavated crater collapses because it becomes so great and the material after the collapse of this leads to the formation of central peaks. 

If we talk about the interior of the crater, it usually has steep walls. Besides these, they also can have giant stair-like terraces that have been formed because of the slumping of walls. The edges of the crater are usually elevated as compared to the surrounding areas. It is also termed a rim. If we talk about ejecta, it is the material of the rock that is basically thrown out of the crater during the impact event and usually thrown out of the rim as debris of the crater on the surface of the planet. 

Crater Definition

Following are some of the definitions for a crater:

• "Crater is the round hole at the top of a volcano, or a hole in the ground similar to this" - Cambridge dictionary.

• "A crater is a very large hole in the ground, which has been caused by something hitting it or by an explosion." - Collins dictionary.

• "Crater is the bowl-shaped depression around the orifice of a volcano or a depression formed by an impact (as of a meteorite) or a hole in the ground made by the explosion of a bomb or shell." - Merriam-Webster

• "A crater is a bowl-shaped depression produced by the impact of a meteorite, volcanic activity, or an explosion." - National Geographic

Simple and Complex Craters

There are different kinds of craters that can be seen. These are generally divided into these two categories. In the former category, they are small-sized and have smooth wall structure with a bowl-shaped appearance. Its size depends upon the planet. The latter are those large craters which are having complex features such as terraces, rings, central peaks, etc. The size of large impact craters is if more than 300 km then they are termed as impact basins. Among the following images, the left one is an example of a simple crater present on Mars whereas the right image is Copernicus which is an example of a large crater present on the Moon.

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Meteorite Crater

These are the pieces of rocks that fall on the Earth from outer space. Some of them burn in the journey before reaching the Earth's surface but some of them pass the atmosphere and reach the surface of the Earth because of which they create a huge depression on the ground. These kinds of the crater are most common on Mars or on the Moon or other planets as compared to the Earth because they usually burn out before reaching the surface of the Earth.

Volcanic Crater

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It is a depression that is caused by volcanic activity in the ground and is circular. It is usually present at the top of the volcano which contains single or multiple vents. Magma erupts from this depression only and it is also deep sometimes. Sometimes at the top of the volcano, lakes are also found in these craters along with some vegetation as well.

Other Types of Craters

There are some other types of craters that can also be found that are described by the scientists:

• The craters in which, in addition to the main basin ring there are multiple basin rings of mountain chains ie. around 5 or 6 rings are surrounded.

• There are craters with irregular shapes whereas there are multiple impact craters that occur at the same time. Impact craters are nothing but meteorite craters.

• There are also craters found which have been eroded because of weathering activities.

• Usually, circular craters are found but elongated craters can occur when the impactor hits the surface at a very low angle, say less than 20°.

Craters on Earth

Different kinds of craters can be found on Earth as there are a number of volcanoes and even meteorites also sometimes reach the surface of the Earth and other types of craters can also be seen as they are one of the most common phenomena in the solar system. Some of the examples are given below:

Meteor Crater

It is also known as the Barringer crater which is present in Arizona with a diameter of 1300 meter and depth of 174 meters. Have a look at the depression of this:

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Diamond Head Crater

It is one of the famous craters found on the Earth that formed because of volcanic activity. It is present in Hawaii and it is an example of a dormant volcano. 

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Kelimutu Volcano

It is also famous for volcanic craters and thus is located in Indonesia at an elevation of 5,377 feet. This is more famous for crater lakes. Here, three acid lakes are found with different beautiful colours such as blue, dark green and red.

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Fun Facts About Craters

• In Astronomy, a crater refers to a kind of constellation that appears like a cup and can be found between the constellations of Hydra and Corvus. The name of this constellation is inspired by the cup that was used to keep the wine in Ancient Greece. The diagram of the constellation is given below.

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• Vredefort impact crater is one of the most famous craters found on the planet Earth and it is the oldest crater which is about 100 km larger present in Johannesburg in South Africa and formed almost over 2 billion years ago. It is not only the oldest but the largest recognised crater on the Earth. Originally, it is believed to be as large as 300 km but now has been eroded.

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Additional Information

• The shapes and sizes of the craters along with the material excavated depend upon various distinct factors. For example, mass, the velocity of the impacting body, surface Geology, etc. If the speed of the impactor is faster then the formation of large craters usually occurs. Generally, objects from outer space hit the surface of the Earth with a speed of 20 km per second and this much speed leads to the occurrence of large craters. On the other hand, it also depends upon the size of the impactor as well. The larger size of the impactor when it hits the surface will create larger craters.

• Craters are very useful in understanding and determining the age of any planet or moon, etc. Scientists note down the size or shape, number of the craters and note how they are eroded, which helps in understanding their history. Usually, more impact craters can be found on older surfaces rather than younger surfaces. For example, the old surfaces of Mercury and Moon have a lot of impact craters. If we talk about the surface of the Earth, it is generally recycled by various geographical phenomena, thus there are few impact craters found.

• If we compare the Earth and the Moon, you will find more craters on the Moon as compared to the Earth. The first reason is the surface of the Moon ( almost 99% ) is older ie. around more than 3 billion years old whereas the surface of the Earth ( almost 80% ) is just 200 million years old. Another reason is there are erosional and weathering activities happening on the Earth which makes it harder to recognise the impact craters on the Earth whereas there is no such activity present, no atmosphere or no tectonic activities happening on the Moon.

Conclusion

Thus, to sum up we can say that a crater can be anything that has a bowl-like structure. It has different meanings in Science, Geography/Geomorphology, History, English, Astronomy, etc. Most commonly this word is used in Geography related to the depression that occurs because of volcanic activities or some object from outer space hits the Earth's surface. There are different kinds of craters that can be found based on their features and geographic occurrence or conditions. This topic will help you in covering one of the important concepts and especially whenever you study volcanoes the meteorites in Science or Geography.