OCEAN FLOOR

 

Far beneath the waves are the mountains, canyons, plains and valleys that make up the ocean floor. This underwater landscape, which is home to as fantastic a diversity of wild creatures as any continent, covers more than 60% of the earth's surface. New features are continually being added to the ocean floor as molten rocks wells up from the earth's hot interior through gaps in the Earth's crust. Once formed, these features change very little, because they soon become covered by protective layers made up of the remain of dead sea creatures that sink to the ocean bottom.

SUBMARINE LANDSCAPE

The ocean floor is really the entire seabed below the low-tide mark, but when people refer to the ocean floor. This is the part of the seabed that lies beyond the continental shelf. Most of the ocean-basin floor is more than 2000 m (6,500 ft) under the water. It is largely flat, but dotted with huge mountains called seamounts.

Continental shelf is the gently sloping area between the edge of a continent and the deep ocean.

Deep ocean trench, formed where one section of the seabed dips beneath another.

Abyssal plain is the smooth sea floor covered with a thick slime called ooze, largely the remains of sea creatures.

GOODS FROM THE OCEAN FLOOR

The seabed is rich in valuable materials and many people are trying to find ways of extracting them. Already 20% of the world's oil comes from beneath the seabed, extracted by oil comes from beneath the seabed, extracted by oil rigs floating on the surface. The rocks of the ocean floor also contain important deposits of diamonds, tin, gold, and billions of tonnes of manganese nodules (rocky lumps rich in metals). Even the mud on the ocean floor contains silver, copper and zinc.

SONAR MAPPING

Scientists known as oceanographers make maps of the ocean floor using sonar (SOund Navigation And Ranging) instruments, which send out pulses of sound that bounce off the seabed and return as echoes. The echoes are used to produce a picture of the ocean floor.

OCEAN FLOOR SURVEY

A survey of the ocean floor uses sonar instruments to reveal the general landscape of the seabed. To see certain features in more detail, oceanographers send down camera sleds carrying video and still cameras and powerful light to pierce and darkness.

MARIE THARP

American oceanographer Marie Tharp (b.1920) collated the results of a large number of surveys to buld up a complete picture of the world's ocean floor. Her painstaking work reavealed the existence of long chains of under sea mountains, now known as mid-ocean ridges.

HYDROTHERMAL VENTS

Down on the ocean floor are strange, chimney like structure that gush dark clouds of Sulphur rich hot water from the earth's interior. These structures are called hydrothermal vents or black smokers. The warm water around these vents provides a home for huge quantities of marine life.