Just like on land, the underwater world has mountains, plains, and deep canyons. This world is not as peaceful and tranquil as people imagine or as it appears on the surface; on the contrary, it is one of the most active and turbulent regions on Earth. Frequent earthquakes and volcanic activity have created towering mountains, but all of this is hidden beneath the sea.
Like land, the ocean floor features various landforms, including mountains, plateaus, basins, and hills. Based on the undulating characteristics of the ocean floor, it can be broadly divided into three parts: the continental shelf, the continental slope, and the ocean floor. The continental shelf refers to the shallow seabed extending from the land into the ocean. The continental slope is the steeper slope between the continental shelf and the deep seabed. The ocean floor is the main part of the ocean, containing positive landforms such as mid-ocean ridges, mid-ocean ridges, and submarine plateaus; as well as negative landforms such as trenches, troughs, and deep-sea basins.
Ocean basins: The main body of an ocean. Basins formed by depressions in the ocean floor and divisions by mid-ocean ridges or submarine uplifts. They are large in area, circular or elliptical in shape, with relatively flat bottoms and depths of 3,000-6,000 meters (mostly 4,000-5,000 meters). They are covered with deep-sea sediments, primarily chemical and biological deposits.
Submarine mountain ranges, also known as mid-ocean ridges or mid-ocean ridges, are long, narrow, and continuous high-lying areas on the deep sea floor. They can stretch for tens of thousands of kilometers, be 1,000-3,000 kilometers wide, and 2,000-4,000 meters high. Some peaks emerge above the water to form islands, such as the Azores in the Atlantic Ocean and Ascension Island in the South Atlantic. The Atlantic Ocean's central submarine mountain range runs north-south, its orientation mirroring the ocean's contours in an S-shape. The Pacific Ocean mid-ocean ridge is located in the central part of the ocean, stretching over 10,000 kilometers from north to south. The Indian Ocean mid-ocean ridge is distributed in a Y-shape.
Ocean trenches are narrow, elongated depressions in the ocean with depths exceeding 6,000 meters. They can stretch for thousands of kilometers and are generally around 100 kilometers wide, with steep slopes on both sides. Ocean trenches often accompany mid-ocean ridges. Mid-ocean ridges emerge above the water to form islands; in the western and northern Pacific Ocean, a series of islands form an arc, creating an island arc. Ocean trenches are generally located on the convex side of an island arc, near coastal mountains or close to islands, at the edge of the ocean. Most ocean trenches are distributed in the Pacific Ocean, especially along the west coast. The deepest ocean trench in the world is the Mariana Trench, southeast of the Mariana Islands in the western Pacific Ocean, reaching a depth of 11,034 meters, a length of 2,550 kilometers, and an average width of 70 kilometers. Areas where ocean trenches are distributed are among the most unstable zones in the Earth's crust, experiencing frequent volcanic eruptions and earthquakes. Xiangshan Port is located north of Xiangshan County, Zhejiang Province. Extending from northeast to southwest into the land, it is approximately 50 kilometers long and only 6 kilometers wide. With six islands forming a natural barrier outside the port, its strategic location makes it one of the best harbors.
