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 answer
Explanation
The correct answer is C, Both 1 and 2. Oceanic trenches mark the places where one plate sinks beneath another, so they are key evidence for plate movement and are lined by volcanoes and earthquakes.
Trenches are the deepest parts of the ocean floor; the Mariana Trench in the western Pacific goes down nearly 11 kilometres. They form at convergent boundaries where a dense oceanic plate is subducted under another plate. As the sinking plate melts at depth, the magma rises to build chains of active volcanoes, such as island arcs, and the grinding plates produce frequent and powerful earthquakes, including deep-focus ones. This is why trenches circle the Pacific along the Ring of Fire and why they are studied closely to understand how plates move.
A is wrong because statement 2 is also correct: trenches are tied to volcanic and seismic activity. B is wrong because statement 1 is also correct: trenches are among the clearest signs of subduction. D is wrong because both statements are true.
Exam tip: trench means subduction at a convergent boundary; mid-ocean ridge means sea-floor spreading at a divergent boundary.
Practice Questions
View allWhich one of the following is not a minor plate ?
- A.Cocos Plate
- B.Nazca Plate
- C.Caroline Plate
- D.Antarctic Plate
Show answer
The Antarctic Plate, carrying Antarctica and the ocean around it, is one of the seven major lithospheric plates. Plate tectonics divides the lithosphere into seven major plates and several minor ones.
Read the full explanation →Which of the following statements with reference to shadow zones in an event of an earthquake is/are correct ? 1. Zone between 105° and 145° from epicentre was identified as the shadow zone for both P-waves and S-waves 2. The shadow zone of P-waves is much larger than that of the S-waves Select the answer using the code given below:
- A.1 only
- B.2 only
- C.Both 1 and 2
- D.Neither 1 nor 2
Show answer
The band between 105° and 145° from the epicentre receives neither P-waves nor S-waves, but it is the S-wave shadow zone that is much larger, so statement 2 is wrong.
Read the full explanation →Which of the following statements about Ring of Fire is/are correct ? 1. It is a zone of convergence plate boundaries 2. It is an active seismic and volcanic zone 3. It is associated with deep trench Select the correct answer using the code given below :
- A.1 and 2 only
- B.2 and 3 only
- C.1 only
- D.1, 2 and 3
Show answer
The Ring of Fire around the Pacific is a belt of convergent plate boundaries, full of active volcanoes and earthquakes and lined by deep ocean trenches.
Read the full explanation →Which one of the following rivers is not a tributary of river Brahmaputra ?
- A.River Manas
- B.River Kameng
- C.River Mahananda
- D.River Subansiri
Show answer
The Mahananda rises in the Darjeeling hills, flows through north Bengal and Bihar and joins the Ganga, not the Brahmaputra.
Read the full explanation →Which of the following statements regarding tropical cyclones is/are correct ? 1. These storms develop during the summer and autumn in every tropical ocean except the South Atlantic and eastern South Pacific Oceans. 2. Tropical cyclones that occur in the North Atlantic and eastern North Pacific Oceans are known as typhoons. 3. Tropical cyclones that occur in the Indian and South Pacific Oceans are called cyclones. Select the answer using the code given below :
- A.3 only
- B.1 and 2 only
- C.1 and 3 only
- D.1, 2 and 3
Show answer
Tropical cyclones of the North Atlantic and eastern North Pacific are called hurricanes, not typhoons, so statement 2 is wrong.
Read the full explanation →