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How Does Biological Weathering Happen?

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Weathering is the process through which rocks, soils, minerals, and other materials are broken down through contact with physical or atmospheric forces, such as pressure and heat, or chemical forces, such as acids. Similar to erosion, weathering can result in caverns, caves, burrows, and other unique rock formations. Biological weathering is a form of both physical and chemical weathering wherein living organisms directly and indirectly cause the decomposition the rock and other materials. Weathering is critical in the movement of nutrients and groundwater, as we'll see a bit later. Common inducers of biological weathering include animals, plants, and strange organisms called lichens.


How Animals Affect Weathering:

A lot of animals physically weather rocks and rock particles. Gophers for example, break apart the earth when they bore underground, separating rock compounds to dig tunnels. Other animals like worms and termites also decompose rocks and minerals in the same fashion. Animal death serves as an indirect form of biological weathering. When animals die, they decay, releasing carbon dioxide into the atmosphere. This carbon dioxide can then combine with water to form carbonic acid, a chemical capable of decomposing minerals.


Plant roots are arguably the most significant cause of biological weathering due to their widespread impact on the earth’s soil.


How Plants Affect Weathering:

Plants weather the earth in a similar way to animals, their roots often being to blame. Plant roots bore into the earth in the same way gophers and worms do, physically shattering rocks and creating cracks throughout the ground. In addition, many plants release acidic and chelating compounds (like organic acids) in order to break down metal-containing particles in the soil. Plants also produce organic acids when they decay, causing further decomposition.


This grassy substance is actually a group of lichens.

This grassy substance is actually a group of lichens.

How Lichens Affect Weathering:

Lichens are composite organisms. This means that lichens consist of two individual organisms that coexist with each other in a symbiotic relationship. Lichens usually consist of fungi and either algae or cyanobacteria (a bacteria that undergoes photosynthesis like plants). Lichens contains microscopic filaments that find their way into small cracks between rocks, repeatedly engorging and shrinking to increase the size of the gaps. This allows more lichens to enter and continue creating fissures in the rock. Lichens also produce oxalic acid, which siphons calcium carbonate from within the rock to its surface and replacing it with a weaker compound, thereby making it easier for the rock to erode. The calcium carbonate is then easily washed away by rain.


This sandstone formation, known as "tafoni," is the result of thousands of years of complex weathering processes.

This sandstone formation, known as "tafoni," is the result of thousands of years of complex weathering processes.

Hint:

Biological weathering sounds an awful lot like erosion, but there is a key difference between the two. Erosion is when the earth’s surface is worn away by moving factors, like running water or wind. Weathering, on the other hand, is a stationary process.


Why Does It Matter?

Biological weathering, and weathering in general, is a crucial process to life on Earth. When rocks are broken down physically or chemically, nutrient rich minerals are released, nourishing plants. Often the types of plants growing in a certain area depend on how the rock and soil have been weathered. The water cycle is also heavily influenced by biological weathering. Agents of biological weathering, plant roots especially, create crevices and tunnels that act as paths used in natural water filtration, cleaning the groundwater that many organisms depend on. As seen with the gopher burrows, biological weathering is an excellent way to create suitable habitats for many creatures; burrows for gophers, caverns for bats, small crevices for plants and lichens - weathering provides all of these diverse homes for the equally diverse organisms that dwell within them.

A Quick Example:

Weathering Quiz:

For each question, choose the best answer. The answer key is below.

  1. Weathering differs from erosion in that...
    • Weathering involves movement while erosion does not.
    • Erosion involves movement while weathering does not.
    • Neither, weathering and erosion are the same process.
  2. What is likely to be the biggest cause of biological weathering?
    • Burrowing animals such as gophers and worms.
    • Oxalic acid produced by lichens.
    • Plant roots embedded in rocks and soil.

Answer Key

  1. Erosion involves movement while weathering does not.
  2. Plant roots embedded in rocks and soil.

Comments

Kaili Bisson from Canada on August 12, 2012:

I really like the connection to plants and animals, and the impact they have. Really well researched and written!

Victoria Lynn from Arkansas, USA on August 05, 2012:

Interesting! I love the photos you chose, too. Well done!

klanguedoc on August 04, 2012:

Great information Btryon86. I have learn something new. You have presented the information in a very well structured way and have explained the concept of erosion and weathering in way that makes it understandable to everyone.

JoyZoeJoy on August 04, 2012:

Very informative for anyone interested in why our planet looks like it does.

Btryon86 (author) on August 02, 2012:

Thanks, I really appreciate the input! It's not something I really knew about until I started researching, but I'm glad I can spread the knowledge now!

KDuBarry03 on August 02, 2012:

Very informative and very interesting! I am not a huge science buff; however, it is importance to know the difference between erosion and weathering as you did. Great job!

Voted up, useful, and interesting!

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