Page 79 - Volcanic Textures A Guide To The Interpretation of Textures In Volcanic Rocks

Fig. 36 Jointing and breccia associated with subaerial andesitic and dacitic lava flows. (A) At the front of a flow,
the massive columnar jointed interior is enveloped in blocky scoriaceous autoclastic breccia and talus. (B) Platy
jointing is parallel to the base in the interior and lower parts of the flow, but steepens at the top and the margins.
Massive lava in the interior is enveloped by blocky autobreccia. Arrows indicate the flow direction. Modified from
Huppert et al. (1982) and Macdonald (1972).

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