The correct answer is Option 1. Explanation & Key Takeaways: • Trenches are found mainly along the coast of the western Pacific Ocean because the western margin of the Pacific Ocean is a subduction zone. • A subduction zone is where two tectonic plates meet, and one plate is forced beneath the other. • The oceanic plate is denser than the continental plate, so it sinks beneath it. • This process creates a deep trench in the ocean floor. • The Peru-Chile Trench is an example of a trench that was formed due to the subduction of the oceanic Nazca Plate beneath the continental South American Plate Related Concepts: Subduction Zone • Subduction is a geological process in which the oceanic lithosphere and some continental lithosphere is recycled into the Earth's mantle at convergent boundaries. • Where the oceanic lithosphere of a tectonic plate converges with the less dense lithosphere of a second plate, the heavier plate dives beneath the second plate and sinks into the mantle. • A region where this process occurs is known as a subduction zone, and its surface expression is known as an arc-trench complex. • The process of subduction has created most of the Earth's continental crust. • Rates of subduction are typically measured in centimetres per year, with rates of convergence as high as 11 cm/year. • Subduction is possible because the cold oceanic lithosphere is slightly denser than the underlying asthenosphere, the hot, ductile layer in the upper mantle underlying the cold, rigid lithosphere. • Once initiated, stable subduction is driven mostly by the negative buoyancy of the dense subducting lithosphere. The slab sinks into the mantle largely under its weight.