Geoscience Reference
In-Depth Information
7
(a)
(b)
Figure 7.8
Columnar joints developed perpendicular to the margin of a near-vertical dyke, Hvalfjorður,
Iceland. (a) General view. (b) Close-up. Coin for scale. (David A. Rothery, The Open University, UK.)
Figure 7.9
The Fingal's Cave fl ood basalt on Staffa, Inner Hebrides,
Scotland. The cliff is nearly 40 m high. The base of the fl ow is the thin,
slightly rubbly horizon at the bottom of the columns (at the roof of the
cave). Columns are remarkably regular in the colonnade forming the lower
15 m of the fl ow, above which the joints of the entablature are more
closely spaced and fan out into a variety of orientations. The original fl ow
was probably virtually horizontal, but has been tilted by about 3° to the
east (right). (David A. Rothery, The Open University, UK.)
