Which of the following rock contain coal and petroleum?

Question

UnlockIAS · Accepted Answer

Correct — D, Layered or sedimentary rocks. Coal and petroleum both form from the burial and compaction of ancient organic matter — plant material for coal, marine organisms for petroleum — within layered sedimentary strata over geological time; sedimentary rocks such as sandstone, shale and limestone act as the source and reservoir rocks for these fossil fuels.

Why the other options are wrong — (a) Granite is a coarse-grained igneous rock that crystallises from cooling magma; it contains no organic matter and cannot host coal or petroleum.  (b) Igneous rocks form from solidifying molten magma or lava at high temperature, a process that destroys organic material rather than preserving it as fossil fuel.  (c) Metamorphic rocks form when existing rocks recrystallise under intense heat and pressure — conditions that typically destroy fossil fuel deposits rather than create them (extreme metamorphism turns coal into graphite).

Concept: Coal and petroleum are fossil fuels that form only in sedimentary settings. Coal forms from thick accumulations of buried plant matter compressed over millions of years; petroleum forms from marine microorganisms buried in sediment and subjected to moderate heat and pressure. Both processes need the layered, low-temperature depositional environment unique to sedimentary rocks — igneous and metamorphic rocks form under conditions that destroy organic matter instead.

State PCS 2021 Q4 — Geography PYQ with Answer

State PCS 2021 Q4 — Geography PYQ with Answer