Canyons are deep, narrow valleys that sometimes contain streams, while caves are dark, cool, and wet places that require specialized adaptations for the creatures living there. Mountains have snow at their peaks and rise sharply from the land, as volcanoes explode lava and eruptions form hard rock. Gulfs are portions of sea almost surrounded by land with a narrow opening, whereas islands are smaller than continents and completely encircled by water. Bays connect to oceans or lakes, and harbors shelter ships from storms in connected bodies of water. Cliffs are tall, steep slopes of rock or soil, and hills form from erosion and are part of raised areas of earth's crust. Glaciers contain ice and have pointed