Tag: Columnar basalt

Illustration of a coastal columnar-basalt outcrop: tightly packed dark stone prisms show mostly six-sided but irregular polygonal tops, tall vertically jointed sides and faint transverse growth markings, beside a cold blue sea beneath a misty sky.

Why Does Cooling Lava Break into Hexagonal Columns?

Cooling basalt contracts and cracks. A moving fracture front turns a roughly hexagonal network into columns that record how the rock lost heat.

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