Biological Weathering
Biological weathering is caused by activities of living organisms and is the weakening and
subsequent disintegration of rock by organisms such as plants, animals and microbes.
There are two main types of biological weathering: mechanical and chemical. Living organisms
can cause both mechanical and chemical weathering to occur. In addition, biological weathering
is more than roots digging in and wedging rocks prying them apart. Instead, biological
weathering can be the actual molecular breakdown of minerals.
Some examples of biological weathering are:
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Plants - growing plant roots can exert stress or pressure on rock. Although
the process is physical, the pressure is exerted by a biological process (i.e.
growing roots). Biological processes can also produce
chemical weathering, e.g. where plant roots or microorganisms produce
organic acids which help to dissolve minerals.
Microbial activity - microbes break down rock minerals by altering the
rock’s chemical composition, thus making it more susceptible to
weathering. One case of microbial activity is lichen; lichen is fungi and
algae, living together in a ‘symbiotic relationship’. Fungi release chemicals
that break down rock minerals; the minerals thus released from rock are
consumed by the algae. As this process continues, holes and gaps
continue to develop on the rock, exposing the rock further to physical and
chemical weathering.
Animals - burrowing animals can move rock fragments to
the surface, exposing the rock to more intense chemical,
physical, and biological processes and so indirectly
enhancing the process of rock weathering. Also, worms,
termites, gophers and prairie dogs can all be responsible for
biologically weathering rocks and rock particles. They
physically break rocks apart during physical activities such as
boring.
Decay - When plants and animals decay, they release carbon dioxide into the air.
When the carbon dioxide mixes with water, it forms carbonic acid, which can
break down the minerals in rocks.
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.
Christian Edwards 10G