Basalt columnar formations

Basalt columnar formations are stunning geological structures formed by slow cooling of volcanic lava.

About this subject

Basalt columnar formations are created when basaltic lava cools and contracts uniformly, producing fractures that form polygonal columns, usually hexagonal. This process, called columnar jointing, occurs on a large scale in areas with ancient volcanic activity.

Famous examples include the Giant's Causeway in Northern Ireland, Fingal's Cave in Scotland, and Devil's Tower in the United States. In Brazil, impressive occurrences are found at Itaimbezinho Canyon in Rio Grande do Sul and in the region of Nova Roma, Goiás, where basalt columns create unique landscapes.

From a geological perspective, these formations indicate ancient lava flows and help scientists understand magma cooling. Culturally, they inspire legends: in Ireland, the Giant's Causeway was built by the giant Finn McCool. Devil's Tower is sacred to several Native American peoples.

Interestingly, the natural symmetry of the columns even influences modern architecture, being replicated in landscaping and construction projects. Some columns reach tens of meters in height, such as those in Aparados da Serra National Park, which stand up to 30 meters tall.

Frequently Asked Questions

What causes the hexagonal shape of basalt columns?

The hexagonal shape results from uniform contraction of lava as it cools. Fractures propagate at 120-degree angles, forming regular polygons that minimize stress, similar to cracks in dried mud.

Where can I see basalt columnar formations in Brazil?

In Brazil, highlights include Itaimbezinho Canyon (RS) in Aparados da Serra National Park, and the Nova Roma region (GO), which has well-preserved columns. There are also occurrences in São Joaquim (SC) and the Serra do Mar range.

What is the largest columnar basalt formation in the world?

The tallest known individual column is at Devil's Tower (Wyoming, USA), standing 264 meters. The largest grouping is the Giant's Causeway (Ireland), which extends for several kilometers.