The vertical features preserved in the basalt flow in the image below formed because the lava ________.
A) was moving as it cooled,so it fractured
B) erupted underwater and cooled rapidly,forming many fractures
C) was subjected to shaking from earthquakes,and subsequently fractured
D) shrank as it cooled,forming tall polygonal-shaped fractures

Question

The vertical features preserved in the basalt flow in the image below formed because the lava ________. 
A) was moving as it cooled,so it fractured 
B) erupted underwater and cooled rapidly,forming many fractures 
C) was subjected to shaking from earthquakes,and subsequently fractured 
D) shrank as it cooled,forming tall polygonal-shaped fractures

Quizplus · Accepted Answer

The tall polygonal-shaped fractures are indicative of columnar jointing, which occurs when the lava cools and contracts, causing vertical fractures to form in a hexagonal or polygonal pattern. This is the result of shrinkage, not movement or shaking.

The Vertical Features Preserved in the Basalt Flow in the Image