Identifying the Non-Plate Boundary: Ninety East Ridge

Plate boundaries are areas where tectonic plates interact. Understanding these interactions is crucial in geology.

Analyzing Geological Features

The question asks to identify which feature among the options is NOT a plate boundary. Let's examine each one:

• Carlsberg Ridge: This is a divergent plate boundary located in the Indian Ocean, marking the boundary between the Carlsberg Plate.
• South East Indian Ridge: This underwater ridge is another divergent boundary, separating the Australian and Antarctic tectonic plates.
• East Pacific Rise: A significant mid-ocean ridge in the eastern Pacific Ocean, it represents a divergent boundary between the Pacific Plate and the Nazca Plate (and Cocos Plate).
• Ninety East Ridge: Unlike the others, this is a linear volcanic mountain range (aseismic ridge) located in the Indian Ocean. It is understood to be a hotspot track, formed as the Indian Plate moved over a stationary mantle plume. It does not represent the direct edge where two major tectonic plates meet and move relative to each other.

Conclusion on Plate Boundaries

Based on the analysis, the Carlsberg Ridge, South East Indian Ridge, and East Pacific Rise are all divergent plate boundaries. The Ninety East Ridge, however, is a hotspot track and not a plate boundary.

Therefore, the correct option is the Ninety East Ridge.