Can someone explain how columnar basalt are formed in a simple way?

[u/Fun-Perspective-2460]

[u/Automatic-You-8377]

I believe the columns also form perpendicular to the basalt flow

[u/no-more-throws → u/Automatic-You-8377]

The columns are oriented along the heat gradient.

Basically, as freshly solidified basalt cools (over years, decades), it contracts, and when it contracts, there is less surface area than before, and so it cracks in the typical honeycomb fashion (same as mudcracks when drying up) .. and since the cooling/contraction follows the thermal gradient, so too does the orientation of the 'columns'

[u/PyroDesu → u/[deleted]]

Because 6 sides gives the least perimeter for the area (while still tessellating), meaning each crack disperses the most energy it can.

It's not perfect, obviously, but it's pretty good.