The ocean floor is a landscape shaped by volcanoes, rift valleys and submerged mountain ranges, but most of the floor is covered in thick, featureless sediment layers. These areas are called the abyssal plains.
The abyssal plains cover over half of Earth's surface, but they are among the least explored areas. Scientists suspect that there are large amounts of biodiversity in these areas, and unique creatures have been discovered at thermal vents along the ocean floor. Life on the bottom of the ocean floor must get its energy from thermal vents or from organic material from life in other parts of the ocean since sunlight cannot penetrate to the depths of the ocean. Small ecosystems can thrive around the body of a whale that has died. In the middle of the abyssal plains are the oceanic ridges. Ridges extend through the ocean floors where tectonic plates pull apart. In these areas, magma flows to the surface and creates basalt rock. Nearer to coasts, the ocean is more shallow and light can actually reach through the water. This area is known as the continental shelf and it is where you will find sea grasses, corals and many varieties of fish.