The oceanic ridge system is a continuous underwater mountain range with parts found in every ocean of the world.
The ridge system is created when magma rising between diverging plates of the lithosphere cools and forms a new layer of crust.
Oceanic Ridge System
The regions below sea level, that we refer to as ocean basins, contain the majority of the planet’s water. If you were to drain all of that water, it would reveal an ocean floor that is far from smooth. In fact, you would see a continuous mountain chain located under the surface of the sea called the oceanic ridge system. This vast mountain range runs through all of the major oceans of the world, and in this lesson, you will learn more about its location as well as how it is formed.
When you stand on the coast and look out over the ocean, you can’t see the ocean floor, but that doesn’t mean there’s nothing happening down there.
In fact, ocean basins are constantly being shaped due to tectonic activity. Tectonic activity is defined as the deformation of the earth’s crust due to the movement of tectonic plates. Tectonic activity is the process that leads to the building of oceanic ridges, so it will be beneficial for us to take a closer look at this process.To strengthen our understanding, let’s take a quick look at how the earth is put together. The earth has an outer crust. When you look at a continent or the ocean floor, you are looking at the earth’s crust.
Beneath the crust is the mantle. The crust and the upper part of the mantle make up the lithosphere, which is the outermost shell of the earth. The lithosphere extends approximately 60 miles below the earth’s surface and is fractured into sections. These plate-like sections of lithosphere are called tectonic plates or lithospheric plates.Below the lithosphere, there is a zone of mantle that consists of semisolid rock that is very hot and deformable, known as the asthenosphere. Because this layer is hot and deformable, the plates of the lithosphere are able to slide over the top of it, somewhat like pucks slide over the top of an air hockey table. If the plates move away from each other, a gap is created.
Hot molten rock, called magma, from the asthenosphere can push up through this gap, and this is the beginning of the formation of an oceanic ridge.
Formation of the Oceanic Ridge System
Magma is the molten rock material that we associate with volcanoes, and essentially what is happening when magma rises up through gaps between the tectonic plates is an underwater volcano. Because these volcanoes erupt into the relatively cool ocean waters, the magma solidifies along the ocean floor and creates new layers of ocean crust. As the magma continues to flow, layers of cooled magma continue to build, forming the rocky mountain-like oceanic ridges, or mid-ocean ridges, as they are sometimes referred to as.
It might help you to recall how oceanic ridges are formed by relating the newly formed rock to a newly formed scab over a cut on your finger. If you cut your finger deep enough, blood will flow out of the wound. This flow of blood is much like the flow of magma from the gap on the ocean floor caused by the separation of the lithospheric plates. As the cut heals, it forms a raised scab.
As the flow of magma cools, it forms a raised layer of crust on the ocean floor.
Distribution of the Oceanic Ridge System
The oceanic ridges of the world are connected and combine to form the oceanic ridge system, making it the longest mountain range in the world, with a total length of approximately 50,000 miles. The continuous oceanic ridge system is distributed around the globe and parts of it can be found in every ocean. The ridge system travels down the center of the Atlantic Ocean, but in the other major oceans, it tends to meander on a course that is at times off-center and somewhat near land masses.
Let’s review. The oceanic ridge system is a continuous mountain chain located under the surface of the sea.
Parts of this vast mountain range can be found in all of the major oceans of the world, including the Atlantic Ocean, where its course follows a path down the middle of the ocean.The earth contains an outer crust that covers a deeper layer called the mantle. The lithosphere is the outermost shell of the earth and is composed of the crust and the upper part of the mantle. Tectonic plates, or lithospheric plates, are plate-like sections of the lithosphere.
Below the lithosphere, there is a zone of mantle that consists of semisolid rock that is very hot and deformable, known as the asthenosphere. Tectonic plates can slide on top of the asthenosphere.At the boundaries between these plates, we see tectonic activity, which is the deformation of the earth’s crust due to the movement of tectonic plates. If the tectonic plates move away from each other, magma from the asthenosphere can push up through the gap causing an underwater volcano.
The magma cools and solidifies, creating new layers of ocean crust that continues to build, forming the oceanic ridges.
After you have finished with this lesson, you should be able to:
- Define the oceanic ridge system
- Describe the earth’s structure, including lithosphere, tectonic plates and asthenosphere
- Explain how oceanic ridges are formed