[Geography Notes] on Lapies Pdf for Exam

Lapies, also termed as Lapiaz, is a weathered limestone surface. When water flows over a surface having limestone along with other hard rocks, lapies are formed. Limestone being a soft rock, erodes the limestone forming several narrow and deep trenches like structures, clints, and grikes dispersed by sharp pin-like vertical pinnacles roughly parallel to each other. Such topography is known as lapies. Their grooves vary in depth from a few millimeters to meters. Their base is extremely hard as they commonly form on tilted rocks. Lapies are peculiar to karst, being related to various karst surfaces but especially those constituted by pure limestone beds of considerable thickness.

Karst Topography

A topography is formed from the process of dissolving or breaking apart soluble rocks such as limestone. It is set apart by underground drainage systems with caves and cenotes. A distinctive topography indicates the breaking apart of underlying rocks by surface or groundwater. Large drainage systems are likely to have both surface and underground or karst drainage components. It generally forms in areas of plentiful rainfall where bedrock comprises carbonate-rich rocks. Some karst topography regions are dominated by several caves. The underground drainage system is one of the remarkable features of the karst regions. The chemical process of solution and precipitation results in the formation of the landforms either through erosion or deposition. The development of such landforms changes from region to region.

Karst topography is known as after the standard topography developed in limestone rocks of the Karst region within the Balkans adjacent to the Adriatic Sea. It includes classic landforms in any dolomitic region, produced by groundwater action through the solution and deposition processes. Limestone is an organically formed sedimentary rock. In its pure state, limestone is formed from calcite or carbonate but where magnesium is additionally present it’s termed dolomite. Limestone is soluble in rainwater.

Limestone Pavement

 A natural karst landform resembling an artificial pavement consisting of a flat, incised surface of exposed limestone, in which the joints have been enlarged. They are made up of a series of clints and are bedrock exposures typically horizontal or gently inclined. The surface has been diffused in water over billions of years into clints or paving blocks with a complex reticulate pattern of crevices between them. The vegetation of limestone pavements is unusual because of the combination of floristic elements including woodland and its edge species. The crevices provide a humid environment favoring woodland plants.

Solved Examples

1. What are the Suitable Conditions For Karst Formation?

Answer:

The conditions are:

• Karst topography is generally found in regions where there is a stretch of water-soluble rocks.

• These rocks may be limestone at the surface or subsurface level. But, the limestone should not be porous.

• These rocks found there should be dense and well-jointed. They should not be thickly bedded. As the rocks found in the karst regions are permeable, the surface water drains underground and erodes the rocks with its horizontal and downward movement.

• An enduring source of water and a low water table to allow the formation of conspicuous features.

• Moderate to abundant rainfall to cause the solvent action of water that is the solution of rocks.

2. What are the Features of Karst’s Topography?

Answer:

• Uvalas-They are long trenches, also termed as valley sinks. Several sinkholes and dolines may combine as a result of subsidence to form a large depression called an Uvalas.

• Lapies-These ridges form due to distinctive solution activity along parallel to sub-parallel joints.

• Limestone Pavements- These structures cause progressive widening and enlargement of joints and cracks in the trenches. It is formed by the solvent action of underground water in the limestones.

• Polije- It is a very large depression in the karst region. These structures are formed by the merging of several uvalas or partly due to faulting.

• Ponor-  This is a natural opening or a portal where a lake or stream flows either completely or partially underground into a karst groundwater system.

• Caves- Limestone dissolves along the bedding planes which is formed due to water percolating down either through materials or through cracks and joints and moves horizontally along with them, resulting in the formation of long and narrow gaps called caves.