Geological works by Underground Water

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Geological Work of Underground Water – 

Underground water refers to water that infiltrates the Earth's surface and occupies the pore spaces, fractures, or cavities within rocks and soil. It acts as a geological agent in shaping landscapes through erosion, transportation, and deposition, particularly in areas underlain by soluble rocks such as limestone, gypsum, and salt.

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1. Sources and Distribution of Underground Water

The sources of underground water include:

1. Meteoric Water: Rainwater or surface water that seeps into the ground.

2. Connate Water: Water trapped in sedimentary rocks during their formation.

3. Juvenile Water: Water derived from magmatic activity deep within the Earth.

Underground water is distributed in two main zones:

Zone of Aeration: The region where the pores in the soil and rock are partially filled with air and partially with water.

Zone of Saturation: The region where all the pores are completely filled with water. The top of this zone is called the water table.

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2. Geological Processes by Underground Water

Underground water performs three main geological processes:

A. Erosion by Underground Water

Erosion occurs primarily through chemical weathering, which involves the dissolution of soluble rocks such as limestone. The main processes involved are:

1. Solution: Minerals dissolve directly into water. For example:

Calcium carbonate (CaCO₃) in limestone reacts with carbonic acid (H₂CO₃) to form calcium bicarbonate (Ca(HCO₃)₂), which is soluble in water.

2. Carbonation: Reaction of carbon dioxide in water with minerals, leading to their dissolution.

As a result of these processes, unique landforms are created:

Caves and Caverns: Large hollow spaces underground formed by the dissolution of limestone.

Sinkholes: Funnel-shaped depressions on the surface, formed when the roof of a cave collapses.

Lapies (Limestone Pavements): Grooved and fluted surfaces on exposed limestone, caused by chemical weathering.

Uvalas: Large depressions formed by the merging of multiple sinkholes.

Poljes: Large, flat-floored depressions formed in limestone terrains, often with intermittent drainage.

Karst Topography: A landscape characterized by features such as sinkholes, caves, and underground streams.

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B. Transportation by Underground Water

Underground water transports dissolved materials (e.g., calcium carbonate, silica, gypsum) as it flows through rocks and soil.

This transportation process is subtle but contributes to the alteration of subsurface environments over geological time.
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C. Deposition by Underground Water

Deposition occurs when underground water loses its capacity to carry dissolved materials. This typically happens when water emerges into open spaces like caves or onto the Earth's surface.
Depositional features include:

1. Stalactites:

These are icicle-shaped formations that hang from the ceilings of caves.

They form when water dripping from the ceiling deposits calcium carbonate as it loses carbon dioxide.

2. Stalagmites:

These are column-like formations that rise from the floor of a cave.

They form when water dripping from the ceiling deposits calcium carbonate upon hitting the floor.

3. Columns or Pillars:

These form when stalactites and stalagmites grow and eventually join.


4. Flowstones:

These are sheet-like deposits of minerals on the walls or floors of caves, formed by water flowing over surfaces.

5. Travertine:

A type of limestone deposited by mineral-rich springs, often forming terraces or mounds.

6. Geyserite and Siliceous Sinters:

Deposits of silica formed around hot springs and geysers due to the evaporation of water.

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3. Features Associated with Underground Water

Underground water creates a variety of landforms, especially in regions with soluble rocks.

A. Karst Topography

Karst landscapes are unique terrains developed in limestone regions due to the action of underground water. Key characteristics include:

Absence of surface drainage (streams sink into the ground).

Presence of sinkholes, caves, and underground drainage systems.

B. Caves and Caverns

These are formed when underground water dissolves soluble rocks, creating large voids.


C. Sinkholes

Formed by the collapse of the surface layer into an underground void.

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