The different types of rocks

The three different types of rocks will be discussed with their specific characteristics and examples.

1. Classification of rocks

2. What are rocks? Hard substance of different materials or minerals held together ( Muneerkpalp , 2015).

3. Does a rock stay the same rock type forever once it formed? (Heath, 2016) No! Due to the rock cycle!

4. Rocks classified according to origin 1)Igneous Rock: Rock formed when molten material cools and hardens and is associated with volcanic activity. Cooling rate controls the crystals size ( Soreda , 2016). Basalt

5. How are Igneous rocks formed? (Teach5ch, 2008)

6. Intrusive igneous rock Deep-lying magma under high pressure, close to the heat source with a slow cooling process. Large crystal formation with granular, coarse texture. Once overlying layers are removed, crystals can be seen. Eg : granite, diorite. diorite

7. Extrusive igneous rocks: More rapid cooling causing smaller crystals to form or no crystals. Volcanic activity is involved. Eg : basalt found on Drakensburg peaks in Lesotho.

8. Sedimentary rock: Rock formed from sediments of other rocks that have been compressed and hardened.

9. Sedimentary rocks: From sediments transported by wind, water, gravity and ice. Three agents: break up rocks, remove the material and deposit this material. Sediments are bound by pressure and infiltrating of cementing material creating a solid rock. Classified by their origin being: mechanical, chemical or organic ( Rahmany , 2020).

10. Mechanical origin Formed from particles (Sand or clay) breaking off existing rocks. Carried by the river into seas and lakes where it gradually settles into layers and becomes compressed. Wind helps to compress the sediments in a desert. Eg : sandstone, shale

11. Chemical origin Form from left behind sediments after evaporation of solutions of dissolved materials occurs. Calcium carbonate is chemically replaced by magnesium forming calcium magnesium carbonate and Weak acids dissolve limestone. When it evaporates underground in caverns such as Congo caves forms stalactites and stalagmites. Eg : limestone, gypsum Limestone Calcium Magnesium carbonate

12. Organic origin Formed by plant and animal remains that accumulated on the sea floor. Coal is formed from dead plant matter. Oil formed from animal remains. Limestone is compacted shells. Oil as well as natural gas is found in sedimentary rocks.

13. Common Characteristics Deposited in layers (Strata) and Contains fossils. The softest and erodes easily. Often form fertile soil. Able to be folded or bent forming fold mountains. Layers are porous and differ in grain size and colour.

14. Uses Coal: For a heat and power source Sandstone: For building Shale: For making roads or paths Salt: Domestic purposes or in chemical industry. Limestone: Cement and fertilisers. Crude oil: Power source

15. Metamorphic rock: Rock developed from igneous or sedimentary rocks that have been altered by heat or pressure.

16. Metamorphic rocks Sedimentary or igneous rock has been exposed to great heat or pressure or both causing their structure to be changed. Magma is forced up, intense heat changing the surrounding rocks Heat combined with pressure to form metamorphism is regional metamorphism. Eg : Magaliesberg mountain with quartzite ridges

17. Rock changes: Great pressure: Shale -> Slate Limestone -> Marble Sandstone -> Quartzite Soft coal -> Anthracite Great heat: Granite -> Gneiss Basalt -> Schist

18. Uses Stone chips for road surface. Slate on roof or garden paths Marble on buildings or sculptures All Gold is found in this rock and is therefore called the banket.

19. https://youtu.be/R-Iak3Wvh9c

20. References Heath, S. (2016). Rock types. Available from: https://www.slideshare.net/stevenheath148/rock-types-67699695?from_search=15 . (Accessed 2023/08/18). M uneerkpalp . (2015). The rock and its types. Available from: https://www.slideshare.net/muneerkpalp/the-rock-and-its-types. (Accessed on 2023/08/18) Rahmany , A. (2020). Types of rock. Available from: https://www.slideshare.net/ArbazRahmany/types-of-rock-227474239. (Accessed 2023/08/18). Soreda , C. M.(2016). The three types of rocks. Available from: https://www.slideshare.net/cyrasoreda/the-three-types-of-rocks-lets-rock-n-roll?from_search=7 . (Accessed 2023/08/18). Teach5ch. (2008). Rock types. Available from: https://www.slideshare.net/Teach5ch/rock-types-presentation?from_search=8 . (Accessed 2023/08/18).