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We all know that rocks weather over time. But which rocks will likely weather the least? Here’s a look at some of the most durable rocks around.
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Igneous rocks
Igneous rocks are made of solidified lava or magma. They are the hardest and therefore the least likely to weather.
Metamorphic rocks
Metamorphic rocks are rocks that have been changed by heat and pressure. These changes can happen deep in the Earth or on the surface. The word “metamorphic” comes from the Greek words “meta” (change) and “morph” (form).
Metamorphic rocks are classified by how they were formed. There are three main types of metamorphic rocks: foliated, non-foliated, and hornfels.
Foliated metamorphic rocks have bands of different minerals running through them. These bands give the rock a “layered” or “sheeted” structure. Slate, phyllite, schist, and gneiss are all examples of foliated metamorphic rocks.
Non-foliated metamorphic rocks do not have bands of different minerals running through them. Marble, quartzite, and novaculite are all examples of non-foliated metamorphic rocks.
Hornfels are a type of metamorphic rock that forms when sedimentary rock is heated so quickly that there is not enough time for crystals to grow.
Sedimentary rocks
Sedimentary rocks are generally more resistant to weathering and erosion than other types of rocks. This is because they are typically composed of harder materials, such as quartz or other minerals, that don’t break down as easily. Also, sedimentary rocks often have a rough surface that helps them to resist being worn away by the elements.
Rock-forming minerals
Rock-forming minerals are those that make up the bulk of the rocks in Earth’s crust. They can be divided into two groups: silicates and non-silicates. Silicates are by far the largest group and include all minerals with the exception of a few, such as calcite, gypsum, and opal. Non-silicates include a variety of minerals such as carbonates, halides, oxides, phosphates, and sulfates.
There are three main groups of rock-forming minerals:
-Silicates: Based on the combination of silicon and oxygen
-Carbonates: Based on the combination of carbon and oxygen
-Halides: Based on a variety of different elements including chlorine, fluorine, and iodine
Weathering processes
Weathering is the process of breaking down rocks, soil, and minerals into smaller pieces by physical or chemical means. It occurs naturally over time and is responsible for creating many of the world’s most stunning landscapes.
There are two types of weathering — physical and chemical — and each one acts on rocks in different ways. Physical weathering breaks rocks apart by freezing and thawing, while chemical weathering alters the composition of rocks.
The type of rock you have will also play a role in how quickly it weathers. Igneous rocks, which are made from cooled lava or magma, tend to be more resistant to weathering than sedimentary rocks, which are made from pieces of other rocks that have been glued together by natural cement-like substances.
That said, all rocks will eventually succumb to weathering if given enough time. The rate at which this happens can depend on a number of factors, including the climate, the type of rock, and its exposure to water and air.
Physical weathering
Physical weathering is caused by the breaking down of rocks by physical means. This can be done by water, ice, wind, and waves. The most common type of physical weathering is fracture damage. This is when the force exerted on rocks is greater than the rocks can withstand causing them to break. When rocks break, they become smaller pieces.
Chemical weathering
Chemical weathering is the breakdown of rocks and minerals into new chemicals. This can happen through reactions with water, oxygen, or other chemicals in the air or in the ground. Chemical weathering is a very important part of the rock cycle, and it can happen to any type of rock.
There are several different types of chemical weathering. One type is called hydrolysis, which happens when water reacts with minerals in rocks to form new minerals. Another type is called oxidation, which happens when oxygen reacts with minerals in rocks to form new minerals. A third type is called dissolution, which happens when chemicals in the ground dissolve minerals in rocks.
Which rocks will likely weather the least? Rocks that are made of resistant minerals, such as quartz or granite, will likely weather the least. These rocks are less likely to undergo chemical reactions because their minerals are not very reactive.
Biological weathering
Biological weathering is a type of mechanical weathering that occurs when plants and animals interact with rocks. Biological weathering can occur in two ways: through the physical activity of plant roots or through the chemical processes of plant and animal secretions. Physical activity from plant roots can break up rocks through a process called rootwedging. In rootwedging, plant roots grow into fractures and cracks in rocks. As the plant continues to grow, the roots force the crack to open wider. This process eventually breaks the rock apart. Chemical processes of plant and animal secretions can also weather rocks. For example, plants secrete acids that can dissolve minerals in rocks.Animal secretions, such as those from birds, can also contain acids that help break down rocks
Factors affecting weathering
There are many factors that can affect how quickly a rock will weather. The type of rock, the climate, and exposure to water are just a few examples. The following is a general guide to the types of rocks that are most resistant to weathering.
· Igneous rocks are generally the most resistant to weathering because they are formed deep underground where they are not exposed to weathering agents.
· Metamorphic rocks are also generally resistant to weathering because they have been modified by heat and pressure deep underground.
· Rocks that contain a lot of quartz tend to be more resistant to weathering than other types of rocks. Quartz is a hard mineral that is not easily broken down by weathering agents.
· Rocks that contain minerals that can be easily dissolved by water (such as gypsum or calcite) are more likely to be affected by Weathering.
Weathering in the natural environment
Weathering is the gradual breaking down of rocks, minerals and organic matter at the Earth’s surface due to the action of wind, rain, snow, ice and other agents. The process is natural and inevitable, but it can be accelerated by human activity.
There are two main types of weathering: physical and chemical. Physical weathering happens when rocks are broken up by the action of forces such as freezing and thawing, plant roots growing in cracks, or the impact of animals or people. Chemical weathering occurs when rocks are dissolved or decomposed by chemical reactions.
The rate of weathering depends on many factors including the type of rock, the climate, the amount of rainfall, the temperature range and whether there is vegetation present. Some rocks weather more quickly than others – for example, limestone is much more susceptible to chemical weathering than granite.
In general, coarse-grained igneous rocks such as granite tend to weather less than fine-grained sedimentary rocks such as shale. This is because it takes longer for water to penetrate through the larger grains in igneous rocks. Igneous rocks that have a high percentage of quartz tend to weather less than those that don’t because quartz is one of the least weathered minerals.
