Duane Shank, age l4, of Lititz, Pa., for his question;

What causes a spring?

The Blue Hole near Castalia is a famous spring that bubbles up from deep below the surface of the ground, It pours forth some 5.,000 gallons of water an hour and its supply comes from far and wide. It is linked to countless other springs and underground streams across our continent.

A single spring is related to a vast system of underground waterways. Its story begins with the pitter patter of falling raindrops and changes to the drip drip drip of seeping water. Later, maybe many years later. the spring gurgles to the surface and perhaps gushes away as a stream. During its lifetime it may travel hundreds of Miles mixing and mingling with oceans of water trapped below the surface of the ground.

every second of every day, more than l6 million gallons of water drop from the clouds. some of this rain refreshes our plants and animals and some falls into the seas. some runs to loin the rivers on their way to the Oceans. And some seeps through the soil to drip through porous rocks below. This is the ground water that rests on solid rocks far below the surface. It rests on top of these deep shelves and basins because it cannot penetrate through their dense, solid rocks.

The floor of the buried ground water may be a few feet or a mile below the surface. Above this floor, the water may be trapped in pockets and crevasses or in the spongy holes of porous rocks. The top level of the buried water is the water table. In moist regions, the rain lifts the water table up close to the surface. The plants can dip down into it and provide lush greenery for the animals. In desert regions, the water table is low and plants on the parched surface perish from thirst.

In many places the water table rises so high that water bubbles out over the ground. It becomes a spring. sometimes a spring gushes forth from the side of a hill where ground water is trapped in porous sandstone. Most springs ooze their way out of the ground. But when the ground water rests in a buried basin of dense rock, the water is under pressure from the sides. Here the springs gush up in fountains. All these springs belong to vast systems of underground waters that move in patterns across the continent.

In parts of Illinois, the farmers Use pumps to bring up the ground water for their crops. The history of this ground water began before Columbus discovered the New World. It began as rain and snow falling upon Wisconsin and Minnesota. some. of the rain and melting snow seeped down through layers of sandstone and became ground water. slowly, this ground water moved toward the central Midwest where the farmers now pump it up from below.