Donna Lanbebn, age 12, of Gary, Indiana, for her question:
What are atolls?
Atolls are children of the sea, of its restless floor and the busy creatures that swarm in its waters. They are islands of a special sort and long before our ancestors voyaged around the world, the people of the Pacific had named them "atolus." We changed their word to "atolls."
Most of the world's atolls are tiny islands strewn about in the vast Pacific Ocean. Early explorers found many of them by chance. Most of them are much too small to merit a place on the ordinary map. Thousands of them have been found and nobody knows how many more have never been seen by man. After all, the vast Pacific covers almost one third of our planet and many atolls are just big enough to grow a couple of palm trees. Others are 10 to 20 miles wide and some are even bigger, but few atolls ever get to be very big islands.
The building of an atoll begins on the bed of the ocean, perhaps two or three miles below the surface waves. It begins when the crust of the earth gets upset. Maybe a submarine volcano erupts or a new mountain begins to hump up its spine. In any case, the bump on the seabed grows higher and higher through the ages. At last it grows almost as high as the surface. Then the story changes. The top of the hump is attacked by tides and pounding waves. The peak of a young mountain is washed away. Cindery debris from the cone of a volcano is swished down after each new eruption. In any case the pounding sea stops the hump from growing tall enough to rise above the waves and become an island of dry land.
The sea appears to win this part of the struggle to create dry land, but the bat¬tle is not over. The hump. now settled just below the tossing waves has friends and helpful allies. The warm waters are populated with assorted corals. And these small, soft bodied creatures build themselves durable homes, preferably in the sunny surface waters. The submerged mountain is just right for them. One of them attaches itself and builds a tiny house of hard coral rock. It multiplies and its children settle down and add their sturdy houses to the first one. Other corals arrive and succeeding generations add their homes. They settle high on the sloping sides of the hump and soon the hump is crowned with a ring of rocky coral formations.
The waves do not bash down the sturdy coral and soon these hard formations poke above the surface. Since the formations are around the edge of the hump, they usually create a ring of dry land with a shallow lagoon of sea water in the middle. This is the atoll. Sometimes there is a break in the coral circle and the atoll is crescent¬-shaped. Winds and waters carry seeds from afar. Some take root on the coral atoll and deck it with tropical greenery. Birds may visit and sometimes the atoll is found by a ship wrecked sailor.
As a rule, where we find one atoll there are others not far away. This is because upheavals in the submarine floor of the sea usually extend over large areas. A moun¬tain peak may be part of a range. A volcano may be one of a chain of fiery sisters. Often there are breaks in an atoll's coral reef and channels from these breaks may connect its lagoon with the lagoons of other atolls.