There are many types of rocks: igneous rocks, sedimentary rocks, and metamorphic rocks. Some rocks are simply huge. Some of them are tiny. Is there a theoretical upper limit on the size of a rock, and what is it based on?

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    $\begingroup$ What do you call a rock? Is a mountain a rock? Is a planet a rock? $\endgroup$ Mar 21, 2023 at 17:34
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    $\begingroup$ I repeat my question. $\endgroup$ Mar 21, 2023 at 17:37
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    $\begingroup$ 10 km is the (terrestrial) limit before a rock (you'd call it a mountain at this point) starts deforming under its own weight. $\endgroup$ Mar 21, 2023 at 17:44
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    $\begingroup$ Would you consider a tectonic plate "a rock"? $\endgroup$ Mar 21, 2023 at 17:47
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    $\begingroup$ If a tectonic plate is a rock for you, then so must be planets... $\endgroup$ Mar 21, 2023 at 17:50

2 Answers 2


In itself, it is very complex to claim what a stone is. However, the industry has to define it. For example, if a track ballast has to be covered with "stones", the stone factory has to know what they have to deliver. Therefore there is the following classification:

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Source: https://en.wikipedia.org/wiki/Grain_size

However, if the geology is to determine how big, for example, rocks or mountains become, it must be taken into account that as the size increases, the surface area exposed to erosion increases, which is one of the limiting factors for rocks or mountains not being able to grow indefinitely high.


Uluru, in central Australia, is also referred to as a inselberg or a monolith. It was once known as Ayers Rock before its indigenous name was adopted.

The dimensions of Uluru are:

  • Length - 3.6 km
  • Width - 1.9 km
  • Height above ground - 348 m
  • Extent into the ground - approximately 2.5 km
  • Perimeter around its contact with the ground - 9.4 km

Less well known is Mount Augustus, in Western Australia, which is another inselberg. Its central ridge is 8 km long and it is approximately 860 m above ground. It covers an area of 4795 ha. It is more than twice the size of Uluru.


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