The deepest known point on Earth, the Challenger Deep, is at the bottom of the Mariana Trench.

The Mariana Trench is a depression in the floor of the western Pacific Ocean, just east of the Mariana Islands. This trench is 1,554 miles long and 44 miles wide. Near its southwestern extremity, lies the deepest point on Earth. This point, the Challenger Deep, plunges to a depth of nearly 7 miles.

In 1960, the Trieste, a manned submersible owned by the U.S. Navy, descended to the bottom of the Mariana Trench. There, the pressure from the weight of the vast ocean above is tremendous. At more than 8 tons per square inch, it's the equivalent of one person trying to hold 50 jumbo jets!

See where the Mariana Trench is located

Ocean MountainsEarth's longest mountain range lies under the sea. Over 56,000 kilometers (35,000 mi) long, this mountain range, called the Mid-Ocean Ridge system, snakes its way around the globe.

The Mid-Ocean Ridge marks the areas where the Earth's crustal plates are moving apart. It is one of the most geologically active areas on Earth. It is where new seafloor is being born, giving rise to hydrothermal vents and volcanoes.


Watch Charting the Vast Oceans: Ocean Floor Geology

Undersea earthquakes and volcanic eruptions can generate catastrophic ocean waves called tsunamis (meaning "harbor wave" in Japanese). During a major quake, the seafloor can move several meters, setting into motion a huge amount of water. The resulting waves may race across the ocean at speeds up to 800 kilometers (500 mi) per hour. The largest tsunami recorded measured 63 meters (210 ft) above sea level when it slammed into Siberia's Kamchatka Peninsula in 1737.
How do you imagine the 'landscape' looks in the ocean? The ocean floor is not flat! In the sea you will find mountain ranges, valleys, volcanoes and much more!

Continents are the landmasses on earth, and earth can be divided into seven continents: North America, South America, Asia, Antarctica, Africa, Europe, Asia, Australia and Antarctica. Each continent extends far beyond the point where the ocean meets the land. This is what we call a continental shelf!  The largest shelf in the ocean is the Siberian Shelf in the Arctic Ocean. This shelf stretches 1500 km (almost a mile) wide.

Geologically, an ocean is an area of oceanic crust covered by water! Oceanic crust is the thin layer of solidified volcanic basalt that covers the Earth's mantle. Continental crust is thicker but less dense.

It is believed that only very little of the ocean floor today is older than 125 million years old!

Geology of the Ocean  
Check out the ocean floor - Click to enlarge the graphic

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The Ocean Bottom

The ocean bottom is divided into three major areas: the continental shelf, the continental slope, and the deep ocean basin.

The continental shelf extends underwater from each of the major land masses. It is the submerged portion of the continents. The shelf has features similar to those we see on land, including hills, ridges, and canyons.

The size of the shelf varies. It may be virtually non-existent in some areas; elsewhere it may extend from shore for several hundred miles. The shelf's average distance is about 64 kilometers (40 mi).

The shelf ends at a depth of about 200 meters (660 ft), giving way to the steeper continental slope, which descends about 3,700 meters (12,000 ft) to the deep ocean basin.

The deep ocean basin is where the ocean floor deepens sharply and its features again resemble those on land, only on a much larger scale, with great plains and mountains.

In fact, the Earth's longest mountain range lies under the sea, the Mid Ocean Ridge system.

Ocean Currents   CURRENTS
  Currents are directed movement of the ocean water caused by wind, temperature and tides.
Ocean Waves   WAVES
  Waves are energy! Energy that moves across the ocean surface as wind drives across the ocean surface.
Ocean Tides   TIDES
  The liquid oceans are pull towards the sun and the moon, this causes tidal bulges in the ocean.
Ocean Gyres   GYRES
  Gyres are huge rotating ocean currents on the ocean surface. There are five main gyres in the World Ocean.
Hydrothermic Vents   HYDROTHERMAL VENTS
  Hydrothermal vents are geusers on the sea floor, bursting with hot hot water into the ocean.