They are due largely to sinkholes or depressions caused by solution of the limestone of the region.
Sometimes the water enters the ground through huge holes called sinkholes.
sinkholes formed by cave-ins over the underground rivers common in the region.
impact craters or sinkholes.
Weathering of the limestone surface created a karst landscape with sinkholes and caves present.
These are sinkholes formed by cave-ins over the underground rivers common in the region.
Mining: Mining can create erosion and sinkholes, as well as contaminate the groundwater.
Oceans are usually full of sinkholes and undercurrents that can pull an unsuspecting swimmer under.
Gordon Warrick at one of the larger sinkholes, Bitter Lake National Wildlife Refuge.
Colonies of swiftlets are also known to roost in at least three limestone sinkholes.
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