Exercise 2

The table below describes six types of sinkholes (Waltham et al., 2005). All occur in karst aquifers. Review the table and decide which types of sinkholes would:

  1. allow direct recharge from sinks to the saturated zone of the karst aquifers?
  2. allow more rapid movement of water to the saturated zone?
  3. slow movement or prevent movement of water into the saturated zone?

Types of sinkholes in karst aquifers (Waltham et al., 2005).

Formation process Host rock type Formation speed Typical maximum size Engineering hazard Other names in use
Solution sinkhole Dissolutional lowering of surface Limestone, dolomite, gypsum, salt Stable landforms evolving over >20,000 years Up to 1,000 m across and 100 m deep Fissure and cave drains must exist beneath floor Dissolution, cockpit, doline
Collapse sinkhole Rock roof failure into underlying cave Limestone, dolomite, gypsum, basalt Extremely rare, rapid failure events, into old cave Up to 300 m across and 100 m deep Unstable breakdown floor; failure of loaded cave roof Cave collapse, cenote
Caprock sinkhole Failure of insoluble rock into cave in soluble rock below Any rock overlying limestone, dolomite, gypsum Rare failure events, evolve over >10,000 years Up to 300 m across and 100 m deep Unstable breakdown floor Subjacent collapse, interstratal karst
Dropout sinkhole Soil collapse into soil void formed over bedrock fissure Cohesive soil overlying limestone, dolomite, gypsum In minutes, into soil void evolved over months or years Up to 50 m across and 10 m deep The main threat of instant failure in soil-covered karst Subsidence, cover collapse, alluvial
Suffosion sinkhole Down-washing of soil into fissures in bedrock Non-cohesive soil over limestone, dolomite, gypsum Subsiding over months or years Up to 50 m across and 10 m deep Slow destructive subsidence over years Subsidence, cover subsidence, alluvial
Buried Sinkhole Sinkhole in rock, soil-filled after environmental change Rockhead depression in limestone, dolomite, gypsum Stable features of geology, evolved over >10,000 years Up to 300 m across and 100 m deep Local subsidence on soft fill surrounded by stable rock Filled, compaction, paleo

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Introduction to Karst Aquifers Copyright © 2022 by Eve L. Kuniansky, Charles J. Taylor, and Frederick Paillet. All Rights Reserved.