From the tropical islands of Hawaii to the frozen continent of Antarctica, mountains and valleys are found throughout the world. Encompassing the highest and lowest places on Earth, each was shaped over hundreds of millions of years by various geologic forces. Some features were built by lava, while others rose along the same fault lines that cause earthquakes. Even the most famous mountains and valleys recognized today are slowly changing over time, sculpted by nature's forces of water, wind, and ice. The fascinating "Mountains and Valleys" explains how a volcano is born under the sea, why Mount Everest is still growing, and what might happen when Africa's greatest valley cracks apart.