Divisions of Ocean Floor 11 Geography Notes

The ocean floor is the vast, largely unexplored surface that lies beneath the world’s oceans. It is a dynamic and complex landscape shaped by the constant forces of plate tectonics, volcanic activity, and erosion. From the shallow continental shelves to the deep ocean trenches, the ocean floor is far from flat, featuring a diverse array of geological formations and ecosystems.

Let us learn more about divisions of the ocean floor!

Divisions of Ocean Floor 11 Geography Notes

What is an Ocean Floor?

The ocean floor is the bottom surface of the ocean basins that cover most of the Earth’s solid surface.

1. It is divided into three main regions:

1. Continental Shelf: A shallow, gently sloping area extending from the coastline.
2. Continental Slope: A steeper region connecting the shelf to the deep ocean floor.
3. Deep Ocean Basin: The deepest part of the ocean floor, consisting of vast, flat abyssal plains.

2. It is not a flat surface but has various features, including:

1. Seamounts (underwater mountains)
2. Guyots (flat-topped seamounts)
3. Hydrothermal vents (hot water and mineral-rich fluids emerging from the seafloor)
4. Submarine canyons (deep valleys on the continental slope)

3. The mid-ocean ridges run through the middle of the ocean basins, where new oceanic crust is formed through volcanic activity at the divergent boundaries of tectonic plates.

4. Trenches, which are the deepest parts of the ocean floor, are found at the convergent boundaries of tectonic plates, where one plate is subducted (pushed under) the other.

5. The ocean floor is constantly changing due to the movement of tectonic plates and volcanic activity, which creates new crust and reshapes the seafloor over time.

Ocean Floor Geography

Along with major divisions, there are also major and minor relief features in ocean floor, which includes:

1. Ridges
2. Hills
3. Seamounts
4. Guyots
5. Trenches
6. Canyons

Continental Shelf

The continental shelf is a relatively shallow and flat area extending from the shoreline.It is covered by relatively shallow ocean water, with an average depth of around 60-185 meters (200-600 feet).The continental shelf gradually slopes downward, with an average gradient of about 0.1°.

It is made up of continental crust, which is typically granitic and less dense than oceanic crust. The width of the continental shelf varies, ranging from a few kilometers to several hundred kilometers. It is an important region for marine life and offshore economic activities, such as fishing and oil/gas exploration.

Continental Slope in details

The continental slope is a steep, inclined region that follows the continental shelf. It connects the shallow continental shelf to the deep ocean basin. The slope usually has a gradient between 3° and 6°, but it can be as steep as 25° in some areas.

It extends from the shelf break (around 200 meters deep) to depths of around 3,700 meters (12,000 feet). The continental slope is often cut by submarine canyons, which are deep valleys formed by erosion and sediment transport. It is an unstable region prone to underwater landslides and turbidity currents.

Deep Sea Plain in details

The deep sea plain, also known as the abyssal plain, is the deepest and flattest part of the ocean floor. It spans vast areas of the ocean basins, covering around 40% of the Earth’s surface. The average depth of the abyssal plains is around 4,000-6,000 meters (13,000-20,000 feet). These plains are covered by thick layers of sediments, mainly composed of clay and the remains of marine organisms.

The mid-ocean ridges, which are underwater mountain ranges, run through the middle of the abyssal plains. The abyssal plains are generally flat, with gentle undulations and occasional seamounts (underwater mountains) and guyots (flat-topped seamounts).

Oceanic Deeps or Trenches in details

Oceanic trenches are the deepest parts of the ocean floor, reaching depths of over 10,000 meters (33,000 feet). They are narrow, elongated depressions found at convergent boundaries, where tectonic plates meet and one plate is subducted (pushed under) the other. Trenches are typically curved or arc-shaped, following the subduction zone.

The Mariana Trench in the western Pacific Ocean is the deepest point on Earth, reaching a depth of around 10,994 meters (36,070 feet). Trenches are characterized by high water pressure, low temperatures, and an absence of sunlight. They are often associated with volcanic activity and earthquakes due to the tectonic processes occurring at the subduction zones.

Conclusion

The ocean floor is a captivating realm that holds many mysteries yet to be unraveled. Its varied topography, from towering seamounts to vast abyssal plains, is a testament to the powerful geological processes that have sculpted the Earth’s surface over billions of years. As we continue to explore and study the ocean floor, we gain invaluable insights into the planet’s past, present, and future, further deepening our understanding of the intricate systems that govern our world.

Divisions of Ocean Floor-FAQs

What is the deepest part of the ocean floor?

The deepest part of the ocean floor is the Challenger Deep, located in the Mariana Trench in the western Pacific Ocean. It reaches a depth of approximately 10,994 meters (36,070 feet) below sea level.

What are seamounts, and how are they formed?

Seamounts are underwater mountains that rise from the ocean floor but do not breach the water’s surface. They are typically formed by volcanic activity, either from hotspots or along mid-ocean ridges.

How are mid-ocean ridges related to the ocean floor?

Mid-ocean ridges are underwater mountain ranges that run through the middle of the ocean basins. They are divergent plate boundaries where new oceanic crust is formed as tectonic plates move apart and molten rock from the Earth’s mantle rises and solidifies.

What are the economic and environmental importance of the continental shelves?

Continental shelves are important for offshore economic activities like fishing, oil and gas exploration, and renewable energy installations. They are also biologically productive regions that support diverse marine ecosystems and play a crucial role in coastal environments.

How does the ocean floor change over time?

The ocean floor is constantly changing due to the movement of tectonic plates, volcanic activity, and erosion. New oceanic crust is formed at mid-ocean ridges, while old crust is subducted (pushed under) at deep ocean trenches. Earthquakes, landslides, and sediment deposition also contribute to the ever-evolving landscape of the ocean floor.