(a) List three types of sedimentary rocks... | WAEC SSCE - Geography - 2021 (Practical and Physical Geography)

Question 1 Report

(a) List three types of sedimentary rocks classified according to their mode of formation.

(b) Name the rocks that are formed when the following undergo metamorphism:
(i) granite;
(ii) clay;
(iii) shale;
(iv) limestone

Answer

(a) Three types of sedimentary rocks classified by mode of formation

Mechanically formed (clastic) rocks - from compacted rock fragments, e.g. sandstone, conglomerate, shale.
Chemically formed rocks - from precipitation of dissolved minerals, e.g. rock salt, gypsum, some limestone.
Organically formed rocks - from remains of plants and animals, e.g. coal, coral limestone, chalk.

(b) Rocks formed when the following undergo metamorphism

(c) Four differences between Sedimentary and Metamorphic rocks

Sedimentary rocks	Metamorphic rocks
Formed by deposition and compaction of sediments.	Formed by alteration of existing rocks under heat and pressure.
Occur in layers or strata (bedded).	Often show banding or foliation, not true bedding.
Usually soft and may contain fossils.	Usually hard, crystalline and fossils are destroyed.
Formed at or near the earth's surface.	Formed deep within the crust under great heat and pressure.

Answer Details

(a) Three types of sedimentary rocks classified by mode of formation

Mechanically formed (clastic) rocks - from compacted rock fragments, e.g. sandstone, conglomerate, shale.
Chemically formed rocks - from precipitation of dissolved minerals, e.g. rock salt, gypsum, some limestone.
Organically formed rocks - from remains of plants and animals, e.g. coal, coral limestone, chalk.

(b) Rocks formed when the following undergo metamorphism

(c) Four differences between Sedimentary and Metamorphic rocks

Sedimentary rocks	Metamorphic rocks
Formed by deposition and compaction of sediments.	Formed by alteration of existing rocks under heat and pressure.
Occur in layers or strata (bedded).	Often show banding or foliation, not true bedding.
Usually soft and may contain fossils.	Usually hard, crystalline and fossils are destroyed.
Formed at or near the earth's surface.	Formed deep within the crust under great heat and pressure.

(a) List three types of sedimentary rocks classified according to their mode of formation. (b) Name the rocks that are formed when the following undergo met...