Figure 4: Evolving breakout morphology 4–10 January 2012.

(a) Map of vertical change over 4–10 January at the lava flow margin. White represents no data and areas with <0.2 m vertical change are transparent, revealing gray-shaded topography in areas of minimal variation. The lava shows overall inflation, with some areas of apparent decrease most probably resulting from horizontal movement of the undulose surface. Horizontal displacements of individually identifiable features are indicated by the arrow trunk lengths, with the greatest velocities associated with the slabby area of the breakout region. The greatest vertical changes, directly to the west of the breakout margin, reflect combined advance and inflation of the flow front. Dashed boxes b and c indicate the location of cross-sections in panels b and c. Scale bar, 50 m in length. (b) Cross-section through the original point cloud data in the zone of greatest vertical change, showing the trajectory (arrows) of labelled topographic features. Scale bar, 10 m in length. (c) Cross-section through the margin of the rubbly lava, showing greatest change of the lava core, which has both advanced and moved downwards. The lava surface (left) has undergone modest advance and little inflation, whereas there is little change in the talus slope. Scale bar, 10 m in length.