Question

How are extrusive and intrusive rocks formed?

Answer 1

Hint:
The extrusive rock can also be defined as the volcanic rock that forms when magma flows outside of the earth and intrusive rocks follow the process of solidification and crystallization.

Complete answer:
The extrusive rocks are finely grained crystal particles that are not easily visible by the human eye. These particles are small in size because of the eruption process. These small particles are also called aphanitic whereas the larger particles are termed phenocryst. Apart from this, the finer particles are termed as groundmass. Some of the other examples of extrusive rocks are scoria, pumice, and andesite. The other rock bodies of extrusive rocks include lava domes, calderas, submarine volcanoes, and shield volcanoes. Examples of intrusive rocks are volcanic necks, laccoliths, sills, dikes, and batholiths. Sometimes, the intrusive rocks are also called plutonic rocks. These rocks usually cover 7% of the land surface. As compared to the extrusive rocks, the intrusive rocks are larger and are also visible to the human eyes. They have a large crystal structure and are also called phaneritic.

Additional Information – At the primary level, the rocks are classified into three types namely Igneous rock, metamorphic rocks, and sedimentary rocks. All these rocks have a different process of formation.

Note:
Examples of igneous rock are pumice, scoria, dacite, and basalt. The example of sedimentary rocks is sandstone, siltstone, shale, and conglomerate. The example of metamorphic rocks is quartzite, marble, gneiss, and phyllite. They are all-natural occurring mas made of solids.