The correct option is 2 and 3 only
Explanation
Mid-Oceanic Ridges (MORs) are continuous underwater mountain chains formed at divergent plate boundaries. They represent the zone where new oceanic crust is generated by the upwelling of magma from the mantle. The morphology of these ridges is distinct and varies based on spreading rates.
Statement-wise Analysis
- Statement 1 is Incorrect. The crest of a typical Mid-Oceanic Ridge (especially slow-spreading ones like the Mid-Atlantic Ridge) is characterized by a deep, steep-walled Central Rift Valley, not a smooth dome. This rift valley is formed due to tensional forces pulling the plates apart. While the ridge system itself is a thermal arch, the specific feature at the crest is a depression (rift), not a smooth dome.
- Statement 2 is Correct. The ridge system forms a broad, elevated zone often described as a fractionated plateau. This terminology refers to the rugged, segmented nature of the ridge, which is cut by numerous transverse transform faults and fractures, giving it a complex, stepped topography rather than a continuous smooth surface.
- Statement 3 is Correct. A flank zone exists along the length of the ridge on both sides. These flanks slope gently away from the elevated crest towards the deep ocean basins (abyssal plains). As the newly formed crust moves away from the crest, it cools, contracts, and subsides, forming these flank zones.
Key Takeaway
Mid-Oceanic Ridges are primarily characterized by a Central Rift Valley (at the crest), a rugged and segmented fractionated plateau, and sloping flank zones leading to the ocean floor.