(a) What is a spring? (b) With the aid of diagrams, describe three ways by which springs may be formed.

Answer Details

(a) What is a spring?

A spring is a natural flow of underground water that comes out onto the surface of the earth, usually at the base of a slope or where the water table meets the ground surface. It marks the point where water stored in permeable rock is forced to emerge.

(b) Three ways by which springs may be formed

• At the junction of permeable and impermeable rock (spring line): Rain water sinks through a permeable layer such as sandstone or limestone until it reaches an underlying impermeable layer such as clay. Unable to sink further, the water flows sideways along the top of the impermeable rock and emerges as a spring where this junction is exposed on a hillside.
• Where the water table cuts the surface: In a valley cut into a permeable rock, the land surface may drop below the level of the water table. Water then seeps out along the valley side wherever the ground level falls below the water table, forming a spring.
• From a dipping aquifer/faulted rock (including artesian): Where a permeable rock (aquifer) lies between two impermeable layers and is tilted, or where a fault brings permeable rock against impermeable rock, water under pressure is forced up along the fault or outcrop and emerges as a spring.

Well-labelled diagrams should show permeable and impermeable layers, the water table, and the point of emergence of the water at the junction of the rock layers.