Oceanic vs Continental Plates: Which is Heavier in Plate Tectonics?

Plate tectonics is the theory that explains the movement of the Earth’s lithosphere, the rigid outer shell that includes the crust and uppermost part of the mantle. The lithosphere is divided into several large pieces, or plates, that move relative to each other. The movement of these plates gives rise to various geological phenomena, including earthquakes, volcanoes, and mountain building. One of the fundamental questions in plate tectonics is whether oceanic plates or continental plates are heavier. In this article, we will explore this question in detail and try to find an answer.

The composition of oceanic and continental plates

To understand which type of plate is heavier, we must first look at their composition. Oceanic plates are made up of dense basaltic rocks that are formed from solidified lava that has flowed from mid-ocean ridges. Continental plates, on the other hand, are composed of lighter granitic rocks, which are less dense than basaltic rocks. The difference in composition is due to the way these rocks are formed. Granitic rocks are formed by the melting and solidification of continental crust, whereas basaltic rocks are formed by the solidification of magma rising from the mantle at mid-ocean ridges.
The density of oceanic plates is about 3 g/cm³, while the density of continental plates is about 2.7 g/cm³. This means that oceanic plates are denser than continental plates. However, this alone does not tell us which type of plate is heavier, because the thickness of the plates also plays a role in determining their weight.

The thickness of oceanic and continental plates

The thickness of the lithosphere varies with the type of plate. Oceanic plates are typically thinner than continental plates, with an average thickness of about 6-7 km. In contrast, continental plates can be much thicker, with an average thickness of about 30-40 km. This means that even though oceanic plates are denser than continental plates, they are not necessarily heavier.

To calculate the weight of a plate, we must take into account both its density and its thickness. The weight of a plate can be determined using the formula

Weight = Density x Thickness x Area

where area is the surface area of the plate. Using this formula, we can calculate and compare the weight of oceanic plates and continental plates.

Which type of plate is heavier?

Using the formula above, we can calculate that the weight of an oceanic plate is about 23 trillion tons, while the weight of a continental plate is about 40 trillion tons. This means that continental plates are heavier than oceanic plates.
The reason for this is that even though oceanic plates are denser than continental plates, their thinner thickness means that their weight is distributed over a smaller area. On the other hand, the greater thickness of continental plates means that their weight is distributed over a larger area, making them heavier overall.

Conclusion

In conclusion, although oceanic plates are denser than continental plates, their thinner thickness means that they are lighter overall. Continental plates, on the other hand, are composed of less dense rock but are much thicker, making them heavier. This has important implications for plate tectonics and the movement of the Earth’s lithosphere, since the weight and thickness of the plates affect the mechanics of their movement and the geological features that result from their interactions.

FAQs

1. What are oceanic plates made of?

Oceanic plates are made up of dense basaltic rocks that form from solidified lava that has flowed out of mid-ocean ridges.

2. What are continental plates made of?

Continental plates are composed of lighter granitic rocks that are less dense than basaltic rocks.

3. Which type of plate is denser?

Oceanic plates are denser than continental plates.

4. Which type of plate is thicker?

Continental plates are typically thicker than oceanic plates.

5. Which type of plate is heavier?

Continental plates are heavier than oceanic plates.

6. How is the weight of a plate calculated?

The weight of a plate is calculated using the formula: Weight = Density x Thickness x Area, where the area is the surface area of the plate.

7. What are the implications of the weight and thickness of plates for plate tectonics?

The weight and thickness of plates affect the mechanics of their movement and the geological features that result from their interactions, such as earthquakes, volcanoes, and mountain building.