Answer:
Oceans have landforms because of volcanic activity.
Step-by-step explanation:
Oceans are dominated by water, but they are not exclusively covered with water on their surface, but there are also a lot of landforms. The landforms are small in the percentage of the total area, but nevertheless, they can be found in varying sizes and shapes. The reason why oceans have landforms is the volcanic activity.
When it comes to landforms that are located near the edges of the oceans, they tend to be created because of subduction zones. Here we have a rise of magma from the mantle and the creation of volcanic island arcs, like in the case of the Japanese islands. When it comes to landforms that are found deep into the ocean and far away from plate boundaries, the cause is hot spot volcanism. This volcanism occurs above places where there is higher than usual activity in the mantle, and it is such a powerful activity that it breaks through the crust and manifests itself on the surface. An example of this type of landforms is the Hawaii Islands.