Bookworms. Nature's formations

Kids love to explore the strange worlds of caves and their fantastical formations. But how do these caverns come to exist? This book will explore the natural processes at work as acids gradually eat away limestone, hollowing out what eventually will become a cave from sheer rock.

About 20,000 years ago, much of North America was covered by glaciers. As the glaciers receded, they scoured the landscape, leaving behind basins that filled with freshwater. Kids will learn about glaciation and how the basins filled. They'll be surprised to learn the Great Lakes, which were carved by glaciers, hold about twenty percent of the world's freshwater.

Like any body of water on land, rivers start with a simple drop of rain. That raindrop might fall into an already existing pond or lake, or it could seep through the ground and come up elsewhere through a spring. A river begins as a trickle that flows downhill. As it flows further, a river becomes wider and deeper. Kids will enjoy tracing the journey of rain from a stream all the way to the sea.