---
basalt:
  id: 01jbq9d3m00000000000000013
title: Giant's Causeway
basalt_note: the apostrophe here is deliberate — it tests key handling
tags: [place, rock]
---
# Giant's Causeway

On the north coast of Northern Ireland, around 40,000 interlocking basalt
columns step down into the sea. They are the eroded remains of a lava plateau
laid down in the Palaeogene, roughly 50 to 60 million years ago.

Most of the columns are hexagonal. Some have four, five, seven or eight sides,
which is the ordinary untidiness described in [[Columnar Jointing]].

The site is a useful illustration of why [[Basalt]] behaves the way it does:
a flow thick enough and uniform enough to cool slowly produced unusually
regular jointing.