The correct option is 1 and 3 only.
Explanation
Submarine canyons are deep, steep-sided valleys cut into the seabed of the continental slope, sometimes extending well onto the continental shelf. These features are significant components of the ocean floor relief, serving as conduits for sediment transport from land to the deep sea.
Statement-wise Analysis
- Statement 1 is Correct: Submarine canyons are often deep gorges that can rival the scale of major land canyons. For example, the Hudson Canyon off the coast of North America is comparable in depth and width to the Grand Canyon of the Colorado River. They typically have V-shaped profiles and steep walls.
- Statement 2 is Incorrect: Submarine canyons are primarily found cutting across the continental shelves and slopes, not the deep sea plains (abyssal plains). While they deposit sediments onto the continental rise or abyssal plain (forming submarine fans), the canyons themselves are features of the continental margin.
- Statement 3 is Correct: The most widely accepted theory for the formation of submarine canyons is erosion by turbidity currents. These are dense, sediment-laden underwater currents that flow downslope at high speeds, carving out the canyon walls much like rivers carve valleys on land.
Key Takeaway: Submarine canyons are erosional features located on continental slopes and shelves, often formed by turbidity currents, and are distinct from deep-sea trenches or abyssal plains.