If you're studying geology, you've probably heard of a mid-ocean ridge . Its concept is explained within a somewhat complex context. It belongs to theories of Earth's formation, such as plate tectonics . These theories are what underpin the origin of mid-ocean ridges.
And it is that an oceanic ridge is nothing more than an underwater mountain range formed by the displacement of tectonic plates. Do you want to know the origin, characteristics and types of ocean ridges that exist on our planet?
Characteristics and origin of an oceanic ridge
When several mid-ocean ridges form beneath the oceans, they create veritable underwater mountain ranges. The world's largest underwater mountain ranges span a distance of 60.000 kilometers . Mid-ocean ridges are separated by ocean basins.
Its origin lies in the movement of tectonic plates that form the Earth's crust . The sediments that accumulate in underwater mountain ranges are at least ten times thicker than those on the continent. This gave rise to the geosynclinal theory. This theory states that the continental crust grows thanks to the progressive and massive accumulations originating from ancient, folded geosynclines. Over time, these have hardened and consolidated into the current plates.
The study of mid-ocean ridges is fundamental to understanding their influence on the Earth's relief.
Structure of the dorsal
The vast majority of these underwater mountain ranges can reach heights of between 2000 and 3000 meters . They typically have a rugged topography, with broad slopes and very steep ridges. When these ridges have a deep indentation, it is called a rift valley . Rifts are prone to numerous shallow earthquakes and volcanic eruptions that release large quantities of basalt.
The basalts give shape to the entire seabed. On the sides of the ridge, the thickness of the volcanic crust and the thickness of the sediments are increasing. There are also underwater volcanoes, but they are scattered and lonely. You don't necessarily have to be in a rift.
The ridges of the ridges can be laterally displaced along more extensive sections that correspond to the fracture zones. When we meet a boundary between two plates, hot, molten lava rises to the surface. Once it arrives, it cools and solidifies while the oldest crust separates on both sides of the ridge.
This is constantly shifting. Proof of this is that the movement of mid-ocean ridges has been measured at certain points in the Atlantic. Displacements of up to two centimeters per year have been recorded. On the other hand, in the eastern Pacific, displacement measurements have been taken, yielding data of 14 cm per year. This means that mid-ocean ridges do not move at the same speed everywhere. The change in the submerged volume of the ridges causes slight modifications to sea level on a geological timescale. When we refer to a geological timescale, we are talking about thousands of years.
Complexity of an ocean ridge
Hydrothermal vents can be found along the crests of mid-ocean ridges. Steam with a high mineral content erupts from these vents at temperatures of 350 degrees Celsius . As the minerals are deposited, they form column-like structures composed primarily of metallic sulfide compounds. These sulfides are capable of supporting colonies of less common animals. These compounds play a vital role in the functioning of marine ecosystems, contributing to a more stable water composition.
The new oceanic crust generated at mid-ocean ridges, along with part of the upper mantle and crust, forms the lithosphere . All marine centers extend along mid-ocean ridges. Therefore, many of the features found in these locations are unique.
They are the subject of many studies. To fully understand the composition and evolution of mid-ocean ridges, basaltic lavas are studied. These lavas are gradually buried by sediments that are deposited across the entire surface. Often, the heat flow is stronger within mid-ocean ridges than in the rest of the world.
Earthquakes are very common along mid-ocean ridges and, especially, along transform faults . These faults connect segments of the compensating ridge. Earthquakes that occur in these areas are studied in depth to gather information about the Earth's interior.
Dorsal dispersion
On the other hand, there is a strong relationship between the depths that an oceanic ridge has with its age. In general, it has been shown that the depth of the ocean is proportional to the square root of the age of the crust. This theory is based on the relationship between age and the thermal contraction of the oceanic crust.
Most of the cooling that led to the formation of mid-ocean ridges occurred about 80 million years ago. At that time, the ocean depth was only 5 km. Today, depths of over 10.000 meters are known. Because this cooling is a function of age, slow-spreading ridges, such as the Mid-Atlantic Ridge, are narrower than faster-spreading ridges, such as the East Pacific Rise.
The width of a mid-ocean ridge can be calculated based on its dispersal rate. Ridges typically expand by about 160 mm per year, which is insignificant on a human timescale. However, it is noticeable on a geological timescale. The slowest-spreading ridges are those that disperse only 50 mm per year, while the fastest expand up to 160 mm.
Slower-spreading ridges have rifts, while faster-spreading ridges don't. Slow-spreading ridges have irregular topography on their flanks, while faster-spreading ridges have much smoother flanks.
As you can see, an oceanic ridge is more complex than it seems. Its dynamics are defined by the constantly moving terrestrial activity .
