Which one of the following is formed when volcanic ash is carried by running water and is deposited as a sedimentary layer ?

Tuff is a volcanic rock formed from the consolidation of volcanic ash and dust ejected during explosive eruptions [4]. While often deposited directly from the air as fallout, volcanic ash can also be transported by running water or pyroclastic flows and subsequently deposited as sedimentary layers [1]. These volcaniclastic sediments, containing more than 25% volcanic fragments, become compacted and cemented into rock over time [1]. In contrast, basalt is an extrusive igneous rock formed directly from the cooling of lava flows [5]. Lapilli refers to gravel-sized volcanic fragments rather than the resulting rock layer [2], and slate is a metamorphic rock derived from shale, not volcanic ash. Therefore, when volcanic ash is transported by water and deposited in layers that later consolidate, the resulting rock is classified as tuff [4].

Sources

1. [2] Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 11: Volcanism > 3) Explosive (Violent Ejection Of Solid Material) > p. 143
2. [4] https://www.nps.gov/joda/learn/nature/geologicformations.htm
3. [1] Certificate Physical and Human Geography , GC Leong (Oxford University press 3rd ed.) > Chapter 2: The Earth's Crust > Chapter 2 The Earth's Crust > p. 18
4. [5] https://www.nps.gov/articles/000/volcanic-ash-tephra-fall-and-fallout-deposits.htm