Which one of the following is formed when volcanic ash is carried by running water and is deposited as a sedimentary layer?
- A.Basalt
- B.Lapilli
- C.Slate
- D.Tuff
Correct answer
Explanation
The correct answer is D, Tuff. Tuff is the rock formed when volcanic ash settles in layers and hardens. During an explosive eruption, fine ash is thrown into the air and falls over a wide area; rain and running water then wash this ash into hollows, valleys and lakes, where it is laid down in beds like any other sediment. With compaction and cementation the ash becomes a light, porous, layered rock called tuff, which shows both volcanic and sedimentary features. It is soft enough to cut, and many old buildings were made of it. Option A is wrong because basalt is a dark, fine-grained igneous rock formed when lava cools quickly at the surface, as in the Deccan Traps. Option B is wrong because lapilli are pebble-sized fragments thrown out by a volcano, not a deposited rock layer. Option C is wrong because slate is a metamorphic rock formed from shale under heat and pressure. Exam tip: ash becomes tuff, lava becomes basalt, shale becomes slate.
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 →