Question

55. Columnar joints in a basaltic lava flow are produced by which process? a. compaction of the flow during burial b. compression-related warming and expansion of the flow c. contraction and tension during cooling of the flow d. none of the above

Answer 1

Answer:

The correct option is: c. contraction and tension during cooling of the flow                              

Explanation:

Columnar jointing is a geological structure that is formed in igneous rocks by the cooling and contraction of the rocks and can also be formed in the cooling lava flows. In this process, the columns or the polygonal prisms are formed by the intersecting, closely-spaced fractures called joints.  

The columns formed can be straight or curved and 3 - 30 meters tall.

Answer 2

Answer:

C. Tension due to cooling of flow,

Explanation:

• These joints on the basaltic rocks through occurring in moistly igneous rock types, created by lava and ash flow. Some Of the famous Columnar joints are found in places like Devil tower, Giant Causeway, and Deccan Traps, etc.  
• Upon cooling these forms These are arranged in regular angles and straight columns.
• And the irregular array is termed as entablature. These condense to form various forms in nature through the cooling and spreading of lavas.