Rocks and other minerals weather in surprising ways when the Earth’s climate changes. A warmer, wetter planet will very certainly witness a wider range of weathering mechanisms, from physical to chemical. The features of weathering will be determined by the mix of rock types and local geologic circumstances, but such a shift will almost certainly result in the creation of new products as well.

The idea that rocks are alive has been around for millennia, with many classifications and classifications of rocks and rock-forming materials. Rocks are seen to be living beings by some because they have unique forms and textures and may be cut, carved, or crushed into usable shapes. Although rocks have these features they are not studied as living beings.

Waves Sea Coast Beach Crashing  - dimitrisvetsikas1969 / Pixabay
dimitrisvetsikas1969 / Pixabay

Physical weathering differs from chemical weathering. Physical weathering degrades rocks without causing them to change their composition. Chemical weathering changes the chemicals that make up the rocks, resulting in fundamentally new materials.

Many people believe that physical weathering is the primary sort of weathering that occurs. However, as a rock cools, it begins to degrade, and chemical weathering typically happens simultaneously. A rock exposed to rain and wind can crumble into gravel and sand in hours, but other rocks can resist harsh weather for years, if not centuries, before totally disintegrating.

What is Chemical Weathering?

Chemical weathering occurs when the chemical composition of rocks is altered. This happens when water interacts with the rocks, causing a physical change. It is responsible for producing secondary products such as clay minerals and soluble salts that dissolve in water. These products are created by direct alteration of the rock or through oxidation and hydrolysis reactions. A similar process also occurs when carbonic acid dissolves limestones and dolostones, creating karst landscapes such as sinkholes and caves.

Godrevy Lighthouse St Ives Bay  - TimHill / Pixabay
TimHill / Pixabay

It’s important to know what makes up your soil because it can impact how often you need to fertilize your garden, whether you need to add more nutrients over time and how much water it will absorb to keep your plants happy and healthy.

Chemical weathering is categorized depending on the chemical reaction that occurs on rocks. They are oxidation, carbonation, acidification, hydration, and hydrolysis.

What is Physical Weathering?

Physical weathering is the physical disintegration of rocks. Types of physical weathering include abrasion, exfoliation, frost wedging, salt crystallization, and biological activity from trees and animals. Effects of heat and cold also play a major role in the physical weathering of rocks.

Sandstone Stone Rock Weathering  - UteFriesen / Pixabay
UteFriesen / Pixabay

What causes Physical Weathering?

There are many reasons for rocks to split into smaller pieces, and these are known as the different causes of physical weathering. The causes can be divided into three categories: changes in temperature, changes in pressure, and biological activity.

How do they differ from each other?

There are many differences between chemical and physical weathering, but here is a couple of the most basic:

  • Physical weathering is the process of mechanical disintegration of rocks, where no chemical changes take place. Chemical weathering occurs when minerals react with substances in the environment – so it’s all about chemical reactions.
  • Chemical weathering tends to be more common in warm, humid climates where there is a good deal of moisture and water trapped among the layers and cracks of rocks because water allows for chemical reactions that don’t occur in drier places.
  • In contrast, physical weathering can happen just about anywhere as long as there is some type of temperature change or disturbance that contributes to cracking.

A Comparison between Physical and Chemical Weathering

One of the best ways to understand weathering is to think about it as a kind of chemical digestion. As you digest food, you break down the fibrous parts into smaller and smaller particles, ultimately leaving behind only the smallest bits of fiber. Chemical weathering similarly acts on rocks.

Storm Coast Rocky Rock Nature  - dimitrisvetsikas1969 / Pixabay
dimitrisvetsikas1969 / Pixabay

In the mechanical digestion of the human body, food is physically broken into tiny parts by means of chewing. In a similar way, physical weathering breaks down rocks into smaller and smaller pieces, eventually leaving only dust.

  • Physical weathering is the mechanism of breakdown of rocks into smaller parts. It’s caused by processes like frost wedging, abrasion, and exfoliation.
  • Chemical weathering involves a chemical reaction with water, oxygen, or carbon dioxide, which breaks down minerals in the rock and changes its composition. More precisely chemical weathering includes carbonation, oxidation, hydrolysis, hydration, and acidification.

Like physical weathering, chemical weathering can break a large piece of rock into smaller fragments. But they also change the crystal structure of individual minerals within the rock itself, creating new minerals and changing their shapes and sizes.

This weathering process can sometimes even change the rock type altogether (this is called mineral transformation). You can think of it as a kind of “dehydration” – chemicals are lost from or added to this crystal structure when a mineral comes into contact with water and/or oxygen.

For example, Feldspar can transform into clay when exposed to water for long periods of time – this process releases potassium ions which are then washed away from the remaining clay particles.

The biggest difference between chemical and physical weathering is that the former involves a chemical reaction to change the rock, while the latter does not.

Physical weathering typically occurs when rocks are broken down into smaller pieces by external forces like temperature changes or the effects of plant roots. Chemical weathering dissolves minerals in rocks and changes their composition.

For example, acid rain reacts with calcium-bearing minerals present in many rocks and forms gypsum (calcium sulfate). Gypsum eventually crystallizes and settles out as crystals around soil particles, creating a new type of soil structure called gypcrete.

Similarities between Physical and Chemical Weathering

  • The main similarity between physical and chemical weathering is that they are both caused by the weather.
  • They are also similar in that they both involve changes to rocks, and this includes the breaking down of rocks.
  • Finally, a third similarity is that they both can lead to erosion.

The two processes play an integral role in soil formation, and the distinction between them is important to consider. But how are they different? Well, a simple way to think of it is this: chemical weathering involves a chemical reaction that results in the rock’s mineral composition being altered, while physical weathering doesn’t change the mineral composition of a rock. The effect of physical weathering is much less permanent than that of chemical weathering—rock will retain its original minerals after being weathered physically but not after being weathered chemically.

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