Atlantic Ocean. Illustration of the Atlantic Ocean and some of the different marine habitats it supports. Anticlockwise from top left: tropical coast; open sea; ocean floor (showing Idiacanthus panamensis and its light-emitting photophores); Mid-Atlantic Ridge; polar water; temperate coast. The Mid-Atlantic Ridge is the longest mountain chain on Earth. It is seen here running from north to south along the ocean floor, with an active volcano at lower left. The Ridge is formed from molten magma that rises from the Earth's interior and slowly pushes apart the Atlantic crustal plates, widening the Ocean. The Florida peninsula can be seen at far left. Iceland is at far right.