Paper Topic:

Geotechnical materials

The crustal rock is usually categorized into three main types , the metamorphic rocks , the igneous rocks and the sedimentary rocks . Each of the above type of rocks is formed in its way and plays a crucial role in the earth crust since they are responsible for the support of the earth life and also are the sources of all the minerals

The igneous rocks are usually crystalline solids that are usually formed from direct cooling of the magma . There is loss of heat meaning it 's an exothermic process that involves phase change

from liquid to solid state . The igneous rocks can be extrusive or intrusive . Intrusive igneous rocks are formed when the molten lava insulate in to the country rock cools slowly to form a huge rock with a coarse texture . The extrusive rocks are formed when the molten lava fall in to the earth surface and cools fast to form fine grains . The points at which the earth is exposed to the coldness space are normally made from the igneous rocks . Igneous rocks are generally the cooled and hardened magma . An example of the igneous rocks is the Half Dome in Yosemite national Park . The classification of the igneous rocks is normally based on the texture and composition . The fine grained igneous rocks are referred to the aphanites their examples include the rhyolites andesite and basalt . The intermediate grained igneous rock includes the dacite and the diabase . The coarse grained igneous rocks which are further referred to as the phaneritic include the granite , diorite gabbro and peridotite . Obsidian is an example of glassy igneous rocks while the pumice and scoria are examples of frothy igneous rocks . The above classification is based on the texture of the igneous rocks . The photo below represents obsidian that is formed due to rapid cooling like that of the extrusive rocks

There are four classes of pumice rocks in reference to classification according to the composition , these are

The felsic , e .g . the rhyolite , granite , obsidian and the pumice

The intermediate , e .g . the andesite , dacite and diorite

The mafic , e .g . the basalt , diabase , gabbro and scoria

The ultramafic , e .g . the peridotite , it 's noted that the conditions necessary for the formation of these kind of igneous rocks do not exist now

The sedimentary rocks are formed underwater either in rivers , oceans or lakes they form as a result of long time accumulation of this debris (mud and sand . They are referred to as secondary rocks because they are formed from accumulation of debris of the already existing rocks . An example of the sedimentary rocks is the Bryce Canyon National Park in Utah . There are three types of sedimentary rocks these are clastic chemical and organic sedimentary rocks . Clastic are sedimentary rocks that are basic that are formed due to accumulation of the clasts . The photo below show sandstone that is one example of clastic sedimentary rocks formed due to cementation and compaction of quartz grains (sand Chemical sedimentary rocks are...

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