Page 94 - Volcanic Textures A Guide To The Interpretation of Textures In Volcanic Rocks

2. Multiple crusts on an andesitic pillow lobe
A "window" through the bulbous front of a pillow
lobe exposes details of multiple crusts. These crusts
(A, B, C) are up to about 10 cm thick and cut by
evenly spaced joints (J). Their outer surfaces display
ropy wrinkles (W). The lower sketch shows the
multiple crusts in a side view (from the left) of the
pillow lobe in the photograph. Crusts can be traced a
few tens of centimeters laterally to their source which
is marked by small transverse scarps (re-entrant). The
sense of asymmetry of the re-entrants indicates the
propagation direction of the pillow lobe.

Collins Bay pillowed lava flow, Nihotupu Formation,
Miocene; Collins Bay, New Zealand.

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