The Atlantic Ocean, a vast body of water covering a significant portion of the Earth, holds many wonders beneath its surface. While we often think of the ocean’s surface, the ocean floor of the Atlantic is a realm of dramatic landscapes and geological features. One of the most defining characteristics of where the Atlantic Ocean lies is the Mid-Atlantic Ridge. This immense underwater mountain range stretches down the center of the Atlantic, claiming about a third of the ocean bed’s width, reaching approximately 1,000 miles (1,600 km) across. It’s crucial to understand that this is just the Atlantic part of a global oceanic ridge system that encircles the Earth.
Diagram illustrating the elements of a continental margin, showing the transition from the continental shelf to the abyssal plain in the Atlantic Ocean.In certain locations, the Mid-Atlantic Ridge rises above the sea level, creating islands. Iceland, a notable example, emerges from the ridge’s crest and features an extension of the central rift valley. Moving eastward and westward from this ridge, at depths of about 12,000 to 18,000 feet (3,700 to 5,500 meters), are basins that appear relatively flat overall. However, the reality of these basin floors is more complex. Some parts are as mountainous as the Mid-Atlantic Ridge itself, characterized by rocky abyssal hills. Other areas are remarkably smooth, forming abyssal plains. These plains are essentially vast expanses of mud that have filled in broad depressions. Adding to the diverse topography are large, ancient volcanoes, sometimes found individually or in rows within the basins. These volcanic structures can rise to become seamounts and, in some instances, islands.
As you move away from the rugged Mid-Atlantic Ridge and approach the continents, the landscape transitions. First, you encounter an abyssal plain, and then the gently rolling surface of the continental rise. These extensive embankments are located at the foot of continents, at depths ranging from approximately 8,000 to 15,000 feet (2,400 to 4,500 meters). They can extend over 300 miles (500 km) wide off the coasts of northwestern Africa, Angola, Argentina, and the Eastern Seaboard of the United States. In other regions, they are considerably narrower. The continental rises in the Atlantic basin are the result of millions of years of weathering, erosion, and sediment deposition from rivers. Significantly, beneath these continental slopes, within sediment accumulations that are 10,000 to 50,000 feet (3,000 to 15,000 meters) thick, lie some of Earth’s largest potential reserves of petroleum, natural gas, and coal.
The Atlantic Ocean also features island arcs like the Lesser Antilles and the South Sandwich Islands. These are geologically unstable regions where some of the Atlantic’s greatest depths are found. Steep-sided, narrow trenches plunge to depths exceeding 25,000 feet (7,600 meters) below sea level, and more than 10,000 feet (3,000 meters) below the adjacent basin floors. Depths greater than 13,000 feet (4,000 meters) are also present in the Caribbean basin, which has both shallow and deep connections to the open ocean. Even parts of the Mediterranean Sea, which connects to the Atlantic through the narrow Strait of Gibraltar, reach these depths. The Strait of Gibraltar is only about 8 miles (13 km) wide at its narrowest point, and the maximum depth on its sill (a submarine ridge between basins) is just over 1,000 feet (300 meters). This partial isolation of large seas near the Mediterranean significantly influences conditions both within these seas and in the broader Atlantic Ocean.
