Why basalts have columnar joints?
Basalt is a basic spouting rock, without quartz, the general thickness is not large, the production was rock, the majority of rock veins, due to iron and magnesium mineral content, rock dense, hard, fragile, easy weathering, by geological structure After the crushing and development, the formation of a typical columnar joint, that is, broken cleavage, is the crustal movement (tectonic movement) signs.
The signs of the different lithologies are not the same.
The second floor of the said wrong, cleavage is for a single mineral, and the joint is the product of the structure, the two are conceptual misunderstanding.
Basalt is a monolithic rock or rock, and there is no fissure or crack. The columnar joint is the product of later tectonic movement.
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First is not joint, but cleavage. Cleavage and molecular structure and grain size have a major relationship. Basalt is a magmatic rock in the rock, to reach the surface after the rapid cooling, are fine particle structure, grain diameter 0.1-1mm. In the role of force is easy to diverge to the surrounding, and showed columnar cleavage.
