Gary Stepien, age 15, of St. Catharines, Ontario, Canada for his question:'

How are drumlins formed?

Drumlins are related to kames and eskers, moraines and fiords. All of these features are earthworks molded by mighty glaciers. The strange bumps and gouges were given their names centuries ago, when people supposed that they had been modeled by Noah's flood. In the mid 1800s, a college teacher named Louis Agassiz challenged the world of science with a startling new theory. He suggested that drumlins and their relatives are the work of enormous glaciers that once covered vast areas of the temperate zone.

We now know that four great ice ages have come and gone during the past million years. But these actual events are hard to imagine    until we behold the mighty remodeling they did to the surface of the earth. Imagine the weight of a glacier, two miles thick and hundreds of miles wide. It crushes and depresses the earth beneath it. What's more, any glacier thicker than 300 feet moves under its own weight, creeping in slow motion like a frozen flood. Its motions reshape the surface like monster bulldozers and plows, sleds and scrapers.

The ice age glaciers sheared hilltops and gouged valleys, dislodged and shifted mountainous tons of rocks and soil. This debris became embedded all through the ice. As the glaciers advanced, they scraped and gouged the hard bedrock below and these scars reveal the direction of the advancing ice.

Drumlins are rounded hills, usually scored with such parallel lines. They were molded when the glaciers were in their hey day. Some were formed by trimming down ancient hills. Others were mounds of glacial drift    mounds of debris that sank down through the ice. In either case, drumlins were compressed under weighty glaciers. Their gently streamlined slopes were molded to reduce friction and allow the massive ice to flow smoothly.

When at last the glaciers began to melt, their embedded debris was dumped and many of these deposits were molded by gushing water and braided streams. Sometimes the melting water chiseled a channel below a waning glacier and rocky debris sank through  the mushy ice and filled the tunnel. Later this formed a long snaky ridge on the ground. Other glacial drift was dumped in long and short ridges, mounds and other characteristic ice age formations.

Moraines are gravelly glacial deposits, carried from afar. Some are ridges, bulldozed by the advancing ice. When the ice melted, ground moraines were strewn on the surface or piled on mounds called kames. Fiords are steep sided gorges carved along shorelines where the glaciers met the sea. The long snaky ridges that formed in glacial tunnels are called eskers.