Holes in Rocks Explained: How They Form and What Causes Them (2023)

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Holes in rocks can form in surprisingly different ways. Potholes are sometimes caused by water erosion - the simplest and most obvious form of pothole formation. But you might be surprised to learn that holes can form in the early stages of rock consolidation. In addition, some holes in the hard and almost indestructible rock can be created by small molluscs. Astonished? to bring on board!

Holes can be found in all three rock types. Holes can be minor and result from weathering. Also, holes in beach pebbles are formed by drilling mollusks. Primary holes are created concurrently with the formation of volcanic rock due to gas bubbles trapped during lava solidification.

Swiss cheese-like seaside cliffs, flat clams and burrowing creatures, champagne corks... See a connection? After reading the following article, you will see the connection and be able to explain many fascinating things.

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Holes in Rocks Explained: How They Form and What Causes Them (1)

Why do rocks have holes?

Holes in the rocks are a sign of the next level ofthe rock cycle.Holes are the result of various natural processes such as water erosion, wind erosion,waves and glacial abrasion, temperature and humidity fluctuations, activity of living organisms, etc.

Holes in rocks are usually a sign of rock weakness. Softer minerals and rock strata can be destroyed much faster than harder ones. Holes are, in most cases, the result of weathering and erosion. Such volcanic rocks as pumice and scoria make their holes during the solidification of lava.

Different processes are responsible for the formation of the hole. Holes are primarily indicators of rock weakness. However, sometimes holes are formed simultaneously with a rock.

Such holes can be considered an integral part of the rock and constitute a distinctive featurevesicular texture, as in the case ofBasalt.

What Causes Holes in Rocks?

It is not correct to assign only one pitting mechanism to all rock types. Holes can form simultaneously with the rock or millions of years later. Different types of rocks undergo different mechanisms of hole formation.

Weathering, represented by water and wind erosion, abrasive wave activity, and drilling and digging activity by living organisms, creates holes in rocks. Holes in rock can also be created simultaneously with rock consolidation, as in the case of basalt, pumice, and waste rock.

Holes formed simultaneously are typical formagmatic volcanic rocksuch as basalt, slag, pumice andSedimentgesteinsuch as sandstone and limestone.

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The tiny holes between individual grains of sand in sandstone rock are called pores. The pores of a rock together form itsporosity, an important property to be known in groundwater, geotechnical studies and petroleum geology.

Holes can form millions of years after rock formation. These minor holes are mostly caused byexogenous processes, mainly weathering and erosion.

Why are there holes in the beach rocks?

Almost perfectly round rocky holes on the beach represent a mystery to all rock lovers. At first sight it is difficult to find a rational explanation for this surrealist formation. However, the inventive nature has an answer.

Holes in rocks on the beach can be created in two ways. Most common is when the holes are caused by boring sponges, burrowing worms, or molluscs such as piddocks. These creatures produce almost perfectly round holes. The second cause of holes is water erosion, which wears away the weakest parts of the rock.

Stones that have a natural hole running through them are known as witch stones. Holes can be caused in nature by boring sponges, burrowing worms, or molluscs likePiddocks.

Piddocks - are the seashells of the familyPholadidae. These piercing shells effectively bore through the rock, which breaks and erodes into cylindrical holes a few centimeters in diameter.

Piddocks live their lives in this shelter, extending their siphons to filter seawater. Bivalvia shells can sometimes be observed in the holes.

In most cases, however, these are dead organisms. Otherwise, mollusks will try to escape when their shelter is about to be destroyed.

PRINCIPAL:Do you know which rocks you find most often on the beach? Check out the list of the most common beach rocks in the following article:

What makes holes in ocean (sea) rocks

Some other larger holes can be observed in the sea. They can be attractive Swiss cheese-like relief shapes. In addition, there can be huge mesmerizing Gothic arches for small boats to pass through.

The mechanism is slightly different from the one described above. There are certainly no molluscs so large that they have such holes. Cheerfully!

Holes in ocean rocks or cliffs are formed by the erosive activity of wind, waves and salt water. Softer rock strata and minerals erode faster, creating intriguing textures and surfaces. Tafoni - is a separate name for a series of holes in a rock formed by the weathering of honeycomb.

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Salt expansion, which works similarly to ice blasting, occurs in areas of high evaporation or near the ocean.

Evaporation causes the salts to come out of solution and grow and expand in cracks in the rock. Salt expansion and wind activity are the main causes oftafoni– a series of holes in the rock.

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What kind of stones have holes?

Holes in Rocks Explained: How They Form and What Causes Them (2)

notypes of rocks(sedimentary, igneous, metamorphic) may be subject to pitting. Here we give some examples of rocks and highlight the individual processes that occur.

Igneous volcanic rocks, such as basalt, pumice, and scoria, have holes called vesicles. Sedimentary rocks such as limestones and sandstones can naturally have tiny holes called pores. Pebbles on the beach have holes created by flatfish. All types of rock can have holes formed by the weathering of soft minerals.

Presence of holes in intrusive rocks

Intrusive rocks can have simultaneous holes formed during the solidification of magma or lava and secondary holes when the rock mass is exposed to salt water, wave abrasion or the activity of living organisms.

Holes in intrusive rocks are not as common because they usually solidify slowly and deep underground under conditions of high pressure. However, sometimes there are holes in the pegmatites. These holes are called miarolitic cavities and are often the source of fine crystals and gemstones.

Usually intrusive rocks likegraniteorgabrothey do not have holes because they are created under high pressure conditions that do not allow for gas bubbles and holes.

However, there is a special type of small, irregularly shaped cavities found in coarse-grained igneous rocks.Pegmatite.

myarolytic cavitiesarise from a dramatic change in pressure. As the pressure decreases, the dissolved gas from the magma can create large, irregularly shaped bubbles. These cavities are called myarolitic.

PRINCIPAL:The ocean and seas are full of interesting rocks. Do you know which rocks are most commonly found in the oceans? Learn more in the following article:

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Presence of holes in igneous (volcanic) rocks

Igneous volcanic rocks have holes formed simultaneously with the solidification of lava. These holes are part of the structure of the rock. Sometimes the holes are big enough to create them.Geoden– beautiful geological formations edged with amethyst crystals.

Holes in igneous volcanic rocks are explained by the presence of dissolved gases. These gases try to escape while the lava is still liquid and are trapped when the lava solidifies. Examples of such rocks are basalt, pumice and scoria. Holes are usually called vesicles.

BimssteinEslagare volcanically extrusive(volcanic)Stone. They form outside the volcano, usually in lava flows. The top of these lava flows becomes very foamy, and as they cool, the lava gases expand and escape, forming air pockets or vesicles in the rock.

The physics of the described process is similar to when you open a bottle of champagne. Due to the pressure difference, gas bubbles are released into the champagne after opening.

Sometimes volcanic rocks look a little like Swiss cheese - they have dozens of holes in them. Molten rock usually contains dissolved gases.

These gases come out of the lava when it is still liquid, but once the lava solidifies, the gas is trapped.

The specific texture of volcanic rock containing many holes is calledvesicular. Blisters filled with minerals are calledHe pushed him away.

How do holes form in rocks?

The classic hole formation process isweatheringand erosion. Various exogenous agents like water, wind, waves, glaciers and living organisms are responsible for the formation of the holes.

The general pitting process is the weathering of softer minerals from the harder matrix. Holes can sometimes be made by sponges or flat clams. Holes in igneous volcanic rock are formed by lava outgassing and rapid cooling. Gas bubbles get trapped in the lava and are perceived as holes.

Sometimesbig mysterious holesseveral meters in size are created by an interesting natural process. The holes are created by circulating water holding a smaller stone or pebble against the large rock. The resulting friction erodes a "hole" in the larger rock.

FAQ about rocks with holes

Still haven't found an answer to your rocks with holes answers? See the section below for frequently asked questions:

What are holes in igneous rocks called?

Holes in igneous rocks formed as a result of solidification of gas bubbles in lava are called lithophysa in siliceous lavas such as rhyolite, in pegmatites a myarolitic cave, in basalt, pumice and ash vesicles; Druses and lumps in the case where the holes are lined with crystals.

What do you call stones with holes in them?

The first group of rocks with very obvious holes that can be found on the beach are called Witch Stones, Adder Stone, Odin Stone, Holey Stone, Witch Stone, Chicken God and so on. The holes are made with hole clams. The second group of rocks are igneous volcanic rocks such as pumice and scoria.

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What Causes Small Holes in Rocks?

There are three main causes of holes in rocks. The first is weathering - soft minerals being eroded by the harder mass. The second - these are gas bubbles trapped in igneous volcanic rocks. The third - these are holes formed by flat sponges, burrowing worms or molluscs such as piddocks.

PRINCIPAL:Have you ever wondered why stones are different colors? And how are these colors created? Learn more about rock colors in the following article:


The formation of holes in rocks can be simultaneous and secondary. At the same time, holes appear in the rock formation. Holes in basalt, pumice, and scoria are the result of gases trapped during lava solidification and are called vesicles.

Epigenetic or minor holes in rocks are the next stage in the life cycle of rocks. All rocks are subject to weathering. Weathering does not work the same for all types of rocks and minerals.

Some softer rocks and minerals break down faster than others. As a result, different pieces of rock disintegrate at different rates. Soft minerals that are eroded first leave holes.

The main climatic factors responsible for the formation of holes are water, wind, waves and glaciers.

Another mechanism of rock formation occurs with the help of living organisms such as molluscs, worms and sponges. These creatures can make holes in rocks. The most common boring creature that causes holes are piddocks - small sea shells of the Pholadidae family.

In summary, here are the main causes of holes:

  1. Gas bubbles trapped during rock solidification.
  2. Soft weathered and weathered minerals in the hard matrix.
  3. Wind and salt water work together on the seaside rocks.
  4. Abrasion of waves on the cliffs by the sea.
  5. Living organisms such as molluscs, worms and sponges bore and burrow.

Take any brick with a hole in it and train your imagination on the history of that hole's formation using one of the five factors above. Nature has many hidden secrets that will surprise you!

PRINCIPAL:Some rocks have holes in the surface, geodes and thundereggs have a hole inside. Do you know the difference between these two stones? Learn more in the following article:

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