Which of the following statements is/are correct? 1. Oceanic trenches are very significant in the study of plate movements 2. Oceanic trenches are associated with active volcanoes and strong earthquakes Select the answer using the code given below :
- (a)1 only
- (b)2 only
- (c)Both 1 and 2
- (d)Neither 1 nor 2
Correct — C, both 1 and 2. Oceanic trenches are the deep, narrow furrows that form where one tectonic plate bends down and slides beneath another, so they trace the convergent (subduction) boundaries and are central to the study of plate movements — statement 1 is true. That same subduction feeds the volcanic arcs and the powerful, often megathrust, earthquakes that ring the Pacific, so trenches are indeed associated with active volcanoes and strong earthquakes — statement 2 is true. Both statements are correct.
- (a)1 only — This drops statement 2, but the subduction that makes a trench also builds the volcanic arcs and triggers the great earthquakes beside it, so statement 2 is also correct.
- (b)2 only — This drops statement 1, but a trench is precisely the surface expression of a subducting plate, which makes it key evidence in the study of plate movements, so statement 1 is also correct.
- (d)Neither 1 nor 2 — Both statements are well established, so rejecting both is wrong; trenches mark plate boundaries and are lined with volcanoes and earthquakes.
Oceanic trenches are long, narrow and very deep depressions on the ocean floor that mark where one lithospheric plate subducts, or slides down, beneath another at a convergent boundary. They are the deepest parts of the oceans and are ringed by volcanic and seismic activity, most famously around the Pacific Ring of Fire.
Both statements describe the same subduction process, so both are true at once. The trench, the subducting slab, the chain of volcanoes and the great earthquakes are all facets of a convergent plate margin. The tempting error is to think an undersea depression and a mountain-like volcano cannot go together, when in fact both are products of the descending plate.
- Oceanic trenches are the deepest ocean features and mark where one plate subducts beneath another.
- They lie along convergent plate boundaries, so they are prime evidence for studying plate movements.
- Subduction at trenches builds volcanic arcs and island arcs and generates the strongest earthquakes.
- The Mariana Trench in the western Pacific is the deepest known part of the oceans.
- A trench is a deep undersea depression, yet it goes hand in hand with volcanoes and earthquakes because all arise from subduction.
- Do not confuse trenches at convergent boundaries with mid-ocean ridges at divergent boundaries.
Asked through statement-correctness on oceanic trenches, subduction, and the link between trenches, volcanoes and earthquakes.
Match List I (Oceanic Trench) with List II (Location): I. Aleutian II. Kermadec III. Sunda IV. S. Sandwich; A) Indian Ocean B) North Pacific Ocean C) South Pacific Ocean D) South Atlantic Ocean.
- (a) I-B, II-D, III-A, IV-C
- (b) I-B, II-C, III-A, IV-D
- (c) I-A, II-C, III-B, IV-D
- (d) I-A, II-D, III-B, IV-C
Answer(b) I-B, II-C, III-A, IV-D — Aleutian in the North Pacific, Kermadec in the South Pacific, Sunda in the Indian Ocean, South Sandwich in the South Atlantic.
A UPSC item built entirely on oceanic trenches — the same feature Q114 tests, here located to their oceans.
- practice — not a real PYQ
Oceanic trenches are typically found at which type of plate boundary?
- (a)Divergent boundary
- (b)Convergent (subduction) boundary
- (c)Transform boundary
- (d)The interior of a plate
Answer(b) Convergent (subduction) boundary — a trench forms where one plate slides beneath another.
- practice — not a real PYQ
The deepest known oceanic trench in the world is the
- (a)Sunda Trench
- (b)Peru-Chile Trench
- (c)Mariana Trench
- (d)Aleutian Trench
Answer(c) Mariana Trench — in the western Pacific, it holds the deepest point of the oceans.