The correct option is 2 and 3 only.
Explanation
Seamounts are prominent relief features of the ocean floor, defined as mountains rising from the seafloor that do not reach the water's surface. They are distinct from islands and other submarine features.
- Statement 1 is Incorrect: Seamounts are volcanic in origin. They are typically extinct volcanoes that rise abruptly from the ocean floor. While sediments may settle on them over time, their primary formation is due to volcanic activity, not sedimentary deposits.
- Statement 2 is Correct: Seamounts are massive geological structures. By definition, they rise more than 1,000 meters above the surrounding ocean floor. They can reach significant heights, often ranging from 3,000 to 4,500 meters. For example, the Emperor Seamounts in the Pacific Ocean are of this magnitude.
- Statement 3 is Correct: The defining characteristic of a seamount is that it remains submerged. It does not break the surface of the ocean. If such a feature rises above sea level, it is classified as a volcanic island. Flat-topped seamounts are specifically termed guyots.
Key Takeaway: Seamounts are submerged volcanic mountains rising at least 1,000 meters from the seafloor; they do not extend above sea level.