Basalt is an igneous rock that forms near the surface of the earth.
The permeability of basalt depends highly on how quickly it is cooled as well as the thickness of the lava flow that formed the rock.
In this article, we’ll discuss the factors that attribute to permeability and how to tell whether or not a specific specimen of basalt is permeable.
Is Basalt Permeable? (EXPLAINED)
What is Permeability?
When a rock is permeable, it means that water can easily pass through it.
Rocks with permeability have holes within their structures, some being larger than others.
These holes create a network within and throughout the rock to allow the water to pass through without hitting an obstacle and stopping.
Permeable rocks have a network of holes which interconnect throughout the entire structure.
For a rock to be permeable, these holes must connect.
Permeability cannot be confused with porosity in that the two are different effects within a rock.
Porosity is created by gases within the rock which causes a bubbling structure to occur.
These bubbles are not connected, however, which only allows the porous rock to consume and trap water.
A permeable rock, on the other hand, is one that allows water to pass through without being trapped.
Other rocks, such as sandstone and limestone, are also considered permeable due to their internal structure.
Rocks do not need to be igneous like basalt in order to be permeable.
Limestone, for example, is a sedimentary rock. while the formation of each rock can directly determine its permeability, having permeability can apply to many different types of stones throughout the solar system.
What is a Basalt Rock?
Basalt is a rock that forms in rapid cooling lava.
It is made up of iron and magnesium, and accounts for over 90% of all of Earth’s volcanic rock.
Basalt is known for having a low viscosity, which can cause quick moving lava flows.
This is due to the low silica content in basalt, and it can create flood zones which can quickly cover vast areas before the molten basalt has time to cool and solidify.
The vast majority of basalt is formed by the pressures of the upper mantle in the earth’s crust weighing onto the mantle.
These stresses cause the melting point to raise as the upper mantle remains firm.
The mantle beneath will begin to shift during tectonic forces, which lead to a decompression event that can lower the melting point at the upper mantle.
This will produce the magma which contains basalt.
Basalt is used in the construction of cobblestones as well as foundations for structures.
Fibers extruded from basalt are used as an alternative for asbestos. In ancient times, basalt was used in pyramids for flooring and statues.
Basalt is also found across Venus and the moon and is the most commonly found rock on Mars.
Why are Basalt Rocks Variable in Permeability?
Not all basalt rocks are similar in their permeability.
The way that they form please a huge part on how well they handle liquids.
There are three main reasons why one basaltic rock can differ from another.
Depending on how quickly the lava flow had cooled, as well as the thickness of the flow, basaltic rocks can form with high or low permeability.
In addition, the interflow zones within the rock also dictate permeability.
The quicker the lava flow cools, the more permeable it will be.
This means that the salt flows that are thinner will have greater permeability than ones that are denser.
Likewise, very thick flows can have more permeability on the surface rather than deep in the center.
Lava flows that cool slowly do not maintain their bubble structure which leads to permeability.
This rapid cooling works directly with the thickness of the flow in how permeability is determined.
When basaltic lava flows are thick, they have a greater chance of remaining dense.
This, again, leads to low permeability.
In order for a basaltic rock to have uniform permeability throughout, it will need to cool rapidly and also have a thin flow.
Interflow zones are the areas between two different basaltic lava flows.
These two separate areas have their own surfaces as they meld and cool together.
Because they have their own thicknesses as well as cooling rates, and interflow zone can be either permeable or non-permeable.
The conditions in which basalt forms can vary greatly, which means that not all basaltic rock is as permeable as the next.
Most basalts, however, does have a certain amount of permeability, even if it is only on the surface.
Dense centers can occur, and they cause non-permeability depending on the factors we discussed.
Basalt is not just and abundant rock on the earth surface, but it is also highly common throughout our solar system.
Basalt has been used for hundreds of years in construction and ornamental design.
It is a strong material that is permeable to some degree, though it can be found to contain a dense, non-permeable center.
Due to cooling temperatures of basaltic lava flow, as well as other lava flows surrounding it, basalt can form in many different ways.
The only way to tell how permeable a rock truly is, especially in the case of a rock which forms in variable conditions, is to test it through water.
Permeable rocks will allow water to pass through, while more dense rocks and even some porous rocks will absorb the water within its channels.
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