Biological Weathering: Types and Examples — Passage

Biological weathering occurs when living organisms break down rocks through physical or chemical processes. Unlike mechanical or chemical weathering alone, this type involves direct biological activity, contributing to soil formation and landscape evolution.

Types of Biological Weathering

1. Physical (Mechanical) Breakdown

○       Plant Roots: Growing roots penetrate cracks, prying rocks apart (e.g., tree roots splitting sidewalks).

○       Burrowing Animals: Creatures like earthworms and rodents expose rocks to further weathering by displacing soil.

1. Chemical Breakdown

○       Lichens & Mosses: Release acids (e.g., oxalic acid. that dissolve minerals in rocks.

○       Bacteria/Fungi: Produce organic acids or chelating agents that weaken rock structures.

1. Human Activities

○       Mining, construction, or even hiking trails accelerate rock breakdown.

Examples

●       Lichen-Covered Boulders (Yosemite National Park): Lichens slowly dissolve granite surfaces.

●       Tree Roots in Ancient Ruins (Angkor Wat, Cambodia.: Roots disrupt stone temples over centuries.

●       Mussel Boring (Coastal Rocks): Marine organisms chemically erode shorelines.

Biological weathering plays a key role in nutrient cycling, enabling ecosystems to thrive. However, it can also threaten archaeological preservation. Understanding these processes helps in conservation and soil management efforts.

Fun Fact: Tree roots can exert pressures of up to 725 pounds per square inch when growing through rock cracks—enough force to lift sidewalks and split boulders! Some lichens that grow on rocks produce acids strong enough to dissolve granite, which is why even the hardest stone monuments eventually show signs of biological weathering.