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Difficulty: Very hardLandform Evolution by Running Water and Underground Water

In Karst geomorphology, subterranean dissolution of limestone leads to distinct underground and surface landforms. Arrange the following stages of subterranean cavern and collapse feature evolution in their correct chronological order from earliest to latest.

  1. 1Percolation of carbonated rainwater through vertical joints and horizontal bedding planes in limestone.
  2. 2Solutional enlargement of rock fractures to form vertical shafts and subterranean conduit networks.
  3. 3Development of extensive horizontal cavern systems along the phreatic zone at the local water table.
  4. 4Precipitation of dissolved calcium carbonate from dripping water, producing stalactites and stalagmites that merge into pillar columns.
  5. 5Progressive structural weakening and cavern roof collapse, exposing subterranean stream channels as karst windows.

Answer

The correct sequence begins with carbonated water percolating through joints, followed by fracture widening into conduit networks, horizontal cavern development at the water table, speleothem deposition and column growth, and culminates in roof collapse forming karst windows.
The sequence correctly reflects the geomorphological progression from microscopic chemical infiltration of carbonated water into limestone joints, through sub-surface conduit and cavern chamber dissolution at the water table, followed by speleothem dripstone growth inside aerated caverns, ending with cavern roof breakdown resulting in karst windows.

Step-by-Step Solution

1
Identify the initial chemical weathering action.
Rainwater absorbing carbon dioxide forms weak carbonic acid that infiltrates limestone bedding planes and vertical joints.
Chemical dissolution cannot occur underground without initial acidic water entry into rock fractures.
2
Trace the subterranean conduit formation.
Acidic groundwater widens joints and bedding planes into vertical shafts and narrow conduit networks.
Initial dissolution follows structural weaknesses before forming large subterranean chambers.
3
Determine cavern chamber creation at the water table.
Lateral water movement at the phreatic boundary dissolves massive subterranean chambers.
Horizontal flow at the water table concentrates dissolution laterally rather than vertically.
4
Sequence the secondary depositional speleothem features.
Degassing of carbon dioxide in subterranean air spaces deposits calcite stalactites, stalagmites, and coalescing columns.
Depositional dripstone features require air-filled cavern vaults created during water table lowering or vadose flow.
5
Identify the final structural collapse landform stage.
Cavern roof collapse exposes the subterranean river flow as a karst window or collapsed sinkhole gorge.
Extreme underground enlargement coupled with roof thinning causes mechanical instability and ceiling breakdown.

Key Concept

Subterranean cavern evolution and cave roof collapse dynamics in karst topography
Estimated Time:2m 0s
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Topics

Landform Evolution by Running Water and Underground Water

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