sumidouros

Sumidouros are natural depressions occurring in karst landscapes, formed by the dissolution of soluble rocks and, in some cases, the collapse of underground caverns. The term, used in Portuguese, commonly refers to sinkholes or dolines and can describe dry basins or water-filled basins with circular to oval outlines.

They arise when acidic rainwater dissolves limestone, dolomite, or gypsum, enlarging joints and forming underground caves. Over time, surface drainage concentrates in the hollow, and the roof of a subterranean void may collapse, creating a new opening. The resulting depression can continue to widen or fill with water, depending on the local hydrology.

Sizes vary from a few meters to tens or hundreds of meters in diameter; depths range from shallow basins to deep shafts. Some sumidouros remain dry; many contain standing or flowing water and can serve as recharge points for aquifers or as conduits for surface runoff into the subsurface. They are dynamic features, sensitive to rainfall, land use, and groundwater levels.

Sumidouros often host distinctive ecological communities, including cave-adapted organisms, and may preserve fossils or human artifacts in their sediments. They are important for understanding karst hydrology and regional geology.

From a safety and planning perspective, sumidouros can pose hazards to infrastructure and agriculture, especially collapses or sudden inflows of water. They are also sites for scientific study and, in some regions, tourism and cave exploration are developed with caution and protection measures.

Researchers study sumidouros within geology, hydrology, speleology, and environmental conservation, recognizing their role in water resources, landscape evolution, and biodiversity.