ARTESIAN WELL

GS 1 – GEOGRAPHY

Why in News?

Recently, significant amounts of water have been gushing out from underground in Jaisalmer, Rajasthan, attributed to the presence of an Artesian Well.

Experts have rejected the idea that the water is linked to the ancient Saraswati River, suggesting instead that the water may be millions of years old, originating from the Tethys Sea, which existed during pre-Vedic times.

Artesian Well

An artesian well is a type of well where water rises naturally to the surface under pressure without the need for pumping. This occurs when water is trapped in a confined aquifer, sandwiched between impermeable layers such as clay or rock.

Formation: Artesian wells are formed when a well penetrates a confined aquifer—a layer of permeable rock or sediment—allowing the water to be under pressure and rise naturally to the surface.

Pressure Mechanism: The water in the aquifer is under pressure due to the weight of the water above it. When a well is drilled, the pressure forces the water to flow upwards through the borehole. Depending on the pressure, the water may flow freely (flowing artesian wells) or be extracted using a pump.

Features of Artesian Well Found in Rajasthan

• Water Eruption: In Rajasthan’s desert regions, the water is confined beneath a layer of sandstone. When the top layer is punctured, water flows upwards due to high pressure, often gushing out like a fountain.
• Ancient Sea Evidence: The water exhibits high salinity, similar to ancient sea or saline groundwater sources. It is believed to originate from the Tethys Sea, which existed approximately 250 million years ago.
• Marine Clay: Along with the water, fine white marine clay with skeletal remains (oozes) surfaced, indicating the ancient marine origin of the groundwater. Sand brought up during the water flow dates back to the Tertiary period (~6 million years ago).

Geological Significance of Jaisalmer

• The region of Jaisalmer was once part of the Tethys Sea, making it geologically significant for ancient marine life. Fossils of giant sharks have been found in Jaisalmer, Japan, and Thailand.
• The sand and marine clay support the idea of ancient sea connections and the presence of marine organisms from prehistoric times.

Key Facts About the Tethys Sea

• Formation: The Tethys Sea formed during the early stages of the Mesozoic Era, particularly during the Triassic period (250 to 201 million years ago).
• Geographic Extent: It extended across present-day Europe, Asia, Africa, and the Middle East, linking the Pacific and Atlantic Oceans.
• Closure: By the Late Cretaceous (~66 million years ago), tectonic shifts led to the closure of the Tethys Sea, contributing to the uplift of the Himalayan mountain range and the Tibetan Plateau.
• Fossil Evidence: The Tethys Sea was rich in marine life, home to early forms of sharks, ammonites, marine reptiles, and other ancient sea creatures.
• Tectonic Impact: The closure of the Tethys Sea played a significant role in the formation of new landmasses and geological structures.