Oceanic crust is the part of Earth's crust that is covered by the ocean. It's two-thirds the size of Earth's surface, but it's less explored than the surface of the moon. Along with continental crust, oceanic crust separates Earth's surface from the mantle, the planet's inner layer containing hot, sticky material. However, these two crusts differ significantly from each other.
In this article we are going to tell you everything you need to know about the oceanic crust, its origin and characteristics.
Structure of the oceanic crust
The average thickness of oceanic crust is 7.000 meters, while the average thickness of continental crust is 35.000 meters. Furthermore, oceanic plates are much younger: they are estimated to be about 180 million years old, compared to the 3.500 billion years of continental plates.
In ancient times, people believed that the bottom of the sea was a great plain. However, over the years, science has been able to determine that oceanic crust also has landforms, just like continental crust.
At the bottom of the ocean, you can find mountains, volcanoes, and trenches . Furthermore, in some cases, strong earthquakes and volcanic activity can even be felt on land. This is related to the study of earthquakes that affect the Earth's crust and their connection to tectonic plate boundaries . In addition, the oceanic crust has unique characteristics that set it apart.
Continental margins and slopes
Although oceanic crust is often thought of as the part of Earth's crust covered by the ocean, it's worth noting that it doesn't actually begin at the coast. In fact, the first few meters behind the shore are also continental crust. The true starting point of oceanic crust is found on a steep slope a few meters or kilometers offshore. These slopes are called continental slopes and can reach depths of up to 4.000 meters.
The area between the shoreline and the slope is called the continental margin. The depths of these waters do not exceed 200 meters, and they contain the greatest variety of marine life. This aspect of the margin is related to the study of the continental crust , which also affects marine fauna. Furthermore, it is important to note that the continental margin and its relationship with the ocean are fascinating aspects to study.
mid-ocean ridge
Mid-ocean ridges are crests of the ocean floor that form when magma from the mantle rises toward the crust and fractures it. Over centuries, this movement has created mountains that stretch for 80.000 kilometers.
The tops of these mountains are fissured, and magma is constantly flowing from the mantle. Due to this, the oceanic crust is constantly renewed, which explains why it is much younger than the continental crust.
As a result of this constant volcanic activity, mid-ocean ridges grow until they rise above the sea, forming features such as Easter Island on the East Pacific Rise and the Galápagos Islands on the Chilean Mid-Ocean Ridge. To learn more about these formations, you can consult the article on mid-ocean ridges , as well as explore their relationship with volcanism in the region.
nether plains
The abyssal plain is the flat area between the continental slope and the mid-ocean ridge. Its depth varies between 3.000 and 5.000 meters. It is covered by a layer of sediments from the continental crust that completely covers the seabed. Thus, all geographical features are hidden, giving it a completely flat appearance.
At these depths, due to the distance from the sun, the water is cold and the environment dark. These characteristics did not prevent life from developing on the plains; however, the specimens found in these areas had very different physical characteristics from those found in other seas. This presents an interesting contrast with the characteristics of the oceanic crust and its origin, and its relationship to ocean trenches.
Guyots of oceanic crust
Guyots are mountains with tree trunks whose summits have been flattened. They are located in the middle of the abyssal plain and can reach a height of 3.000 meters and a diameter of 10.000 meters . Their distinctive shape emerges when they reach a sufficiently high surface and are slowly eroded by waves into a flat surface. The waves have even worn down the mountain peaks so much that they are sometimes submerged 200 meters below the surface. This phenomenon is directly related to the process of volcanic island formation and erosion.
marine or abyssal trenches
Abyssal trenches are narrow, deep fissures in the seafloor, up to several kilometers deep. They are created by the collision of two tectonic plates, which is why they are usually accompanied by a lot of volcanic and seismic activity, which can cause huge tidal waves, which are sometimes felt on the continents. In fact, most trenches are located near the continental crust because they are created by the collision of oceanic and continental plates.
Especially along the western edge of the Pacific Ocean, lies the deepest trench on Earth: the Mariana Trench, which is over 11.000 meters deep. This aspect of ocean trenches is crucial for understanding how they form and their impact on the environment, as well as their relationship to the phenomenon of Earth's structure and continental drift.
Underwater scientific exploration in the oceanic crust
Throughout history, the oceanic crust has been one of humanity's greatest mysteries, due to the difficulty of diving into the cold, dark depths of the ocean. That's why science is hard at work designing new systems to better understand the geography of the seafloor and how it originated.
Early attempts to understand the seabed were rudimentary: from 1972 to 1976, scientists aboard HMS Challenger used a 400,000-meter-long rope to submerge it in the ocean and measure its bottom point.
In this way, they can learn about depth, but the process must be repeated at different locations to map the seafloor. Of course, the activity is expensive and exhausting. However, this seemingly primitive technology has allowed people to discover the deepest place on the entire surface of the earth - the Mariana Trench.
Today, more sophisticated methods exist. For example, scientists at Brown University were able to explain volcanic activity at mid-ocean ridges thanks to studies of earthquakes in the Gulf of California.
This study and other research supported by scientific tools such as seismographs and sonar are leading to an ever-increasing understanding of the mysteries of the deep ocean , even if it is impossible to dive into it.
