Oceans hide the most amazing underwater landscapes. Just like the continents, the ocean floor has its own plains, valleys, mountains, and canyons. The size of them can be astounding. There are undersea mountain chains that run for miles (km), trenches deep enough to swallow up Eartha's tallest peaks, and vast plains that seem to stretch to infinity. Also hidden beneath the waves are thousands of volcanoes, many more than on the continents. When completely covered by water, these volcanoes are called undersea mountains. When their peaks are tall enough to break the surface of the water, they are called islands. |