Rocks and Meteorites- A Comprehensive Guide

1. Briefly describe the processes that lead to the formation of igneous, 

Sedimentary, and metamorphic rocks 

Igneous rocks are formed as a result of magma condensation and crystallization, and they vary in size and composition. On the other hand, sedimentary rocks can form through clastic material, cementing with elements from evaporation and chemical precipitation since they are linked with the liquid that helps in transportation, erosion, and deposition. Metaphoric rocks are formed from preexisting sedimentary and igneous rocks in the Earth’s crust due to temperature and pressure changes ( Hasterok, Gard & Webb, 2018 ). 

2. Explain partial melting and the geological processes that lead to melting 

Partial melting is the incomplete liquefying of the parent rock due to the differences in the chemical composition. Flux melting and decompression are the major causes of partial melting, with the later involving the rock being at the same temperature while reducing the pressure as it moves towards the surface. In the former, flux, which supports melting, is added to a rock when it is near to its melting point, influencing partial melting to start ( Cruz-Uribe et al., 2018 ). 

3. Describe, in general terms, the range of chemical compositions of magmas 

There are different kinds of magma; they include andesitic magma, basaltic, and rhyolitic magma with their chemical compositions varying from one type to another. Basaltic magma contains sulfur dioxide varying between 45 and 55 percent, low potassium, high iron, magnesium, sodium, as well as Calcium. Andesitic magma has Sulphur dioxide ranging between 55 to 65 percent, moderate iron, magnesium, sodium, potassium, and Calcium. On the contrary, rhyolitic magma has sulfur dioxide between 65 and 75 percent, it has low iron, but high in potassium, it also contains magnesium, sodium, and Calcium ( Jackson, Blundy & Sparks, 2018 ). 

4. Discuss the processes that take place during the cooling and crystallization of 

magma, and the typical order of crystallization according to the Bowen reaction 

series 

After an eruption, magma starts to cool when the temperature begins to hit below 1300 o C, and at this stage, minerals start crystallizing. However, the minerals condense at different temperatures, and this explains why magma fluid contains crystals through the fluid may condense, forming a porphyritic texture. According to the Bowen reaction series, the continuous series and discontinuous series are major pathways for mineral formation as magma cools ( Jackson, Blundy & Sparks, 2018 ). 

5. Explain how magma composition can be changed by fractional crystallization 

and partial melting of the surrounding rocks 

In fractional crystallization, elements crystallize at different rates causing different rates, and these crystals are denser than magma; unused components continue flowing changing composition of the magma. On the other hand, partial melting takes place when parts of a rock melt; thus, in the process, some components mix with the magma changing its composition ( Jackson, Blundy & Sparks, 2018 ). 

6. Apply the criteria for igneous rock classification based on mineral proportions 

Depending on the mineral proposition, igneous rock can be classified as mafic, intermediate, ultramafic, and felsic. The composition content of ferromagnesian silicate, K-feldspar, quartz, and plagioclase differs from one kind of igneous rock to another ( Hasterok, Gard & Webb, 2018) 

7. Describe the origins of phaneritic, porphyritic, and pegmatitic textures 

The phaneritic texture is formed as a result of magma cooling beneath the Earth’s surface, forming large crystals. Porphyritic texture results from conditions changing relatively quickly to an extent it causes rapid crystallization. On the other hand, pegmatitic texture forms in the cooling process when minerals condense massively ( Cardarelli, 2018 ). 

8. Explain the relationships between plate tectonics, the formation of magma, 

and volcanism 

Plate tectonics involves the theory that explains that Earth is alienated into plates that slide along the mantle and the inner rocky layer. Magma is formed through rocks melting in Earth’s lithosphere, and volcanism involves the eruption of magma onto the Earth’s surface ( Jackson, Blundy & Sparks, 2018 ). 

9. Describe the range of magma compositions formed in differing tectonic 

environments, and discuss the relationship between magma composition (and gas 

content) and eruption style 

Magma compositions differ depending on tectonic settings; for instance, at divergent boundaries, felsic melts rarely occur, and at subduction zones, magma interacts with crustal rock changing its composition. Moreover, magma composition and gas content determine the eruption style due to changes in viscosity and pressure. Magma composition changes thickness, which determines the flow since a less viscous fluid flows fast when compared with a more viscous one ( Jackson, Blundy & Sparks, 2018 ). 

10. Briefly identify the types of hazards posed to people and to infrastructure by 

the different types of volcanic eruptions 

Volcanic eruptions pose different kinds to humankind and infrastructure due to lava flows; pyroclastic flows, debris flows, landslides, volcanic gases, tephra, as well as ash. Volcanic gases such as Sulphur dioxide harm human health, whereas the material released during eruptions affects social activities and infrastructure ( Hayes et al., 2020 ). 

References 

Cardarelli, F. (2018). Rocks and Meteorites. In  Materials Handbook  (pp. 1313-1368). Springer, Cham. 

Cruz-Uribe, A. M., Marschall, H. R., Gaetani, G. A., & Le Roux, V. (2018). Generation of alkaline magmas in subduction zones by partial melting of mélange diapirs—An experimental study.  Geology ,  46 (4), 343-346. 

Hasterok, D., Gard, M., & Webb, J. (2018). On the radiogenic heat production of metamorphic, igneous, and sedimentary rocks.  Geoscience Frontiers ,  9 (6), 1777-1794. 

Hayes, J. L., Wilson, T. M., Deligne, N. I., Lindsay, J. M., Leonard, G. S., Tsang, S. W., & Fitzgerald, R. H. (2020). Developing a suite of multi-hazard volcanic eruption scenarios using an interdisciplinary approach.  Journal of Volcanology and Geothermal Research ,  392 , 106763. 

Jackson, M. D., Blundy, J., & Sparks, R. S. J. (2018). Chemical differentiation, cold storage and remobilization of magma in the Earth’s crust.  Nature ,  564 (7736), 405-409.