Figure 14.10
Columnar jointing. This photo shows a small portion of the island of Staffa, in the Inner Hebrides of northwestern Scotland. Most of Staffa is composed of mafic lava that slowly cooled 55 million years ago, allowing time for columnar jointing to form. Here, the joints mainly sit perpendicular to the cooling surface.(© Photo by Lady of the Dawn/Flickr Open/Getty Images)