First 3D imaging characterization of Pele's hair from Kilauea volcano (Hawaii).

In this work the morphologic features of Pele's hair formed during three different eruptions of Kilauea volcano have been investigated: fountaining from Kilauea Iki's 1959 Episode 1, weak explosive activity from Halemaumau lava lake and littoral explosions at Waikupanaha (2009). Morphological studies were performed by optical, stereo- and scanning electron microscopy. For the first time 3D image analysis was carried out by synchrotron radiation X-ray computed microtomography, which allowed a high-resolution 3D reconstruction of the internal structure of each Pele's hair, highlighting several differences in terms of number density, elongation and shape of the vesicles between the samples from the three eruptions. We identified three main parameters determining these differences: initial size of the magma droplet, ejection velocity and magma viscosity. Pele's hair erupted during the Kilauea Iki's fountaining shows the highest thickness and the least elongated shape of the vesicles, though it is related to fast ejection of a low viscosity magma. We therefore suggest that the size of magma droplets is the main parameter influencing the morphology and inner textures of the Pele's hair. The comparison with Pele's hair of similar eruptions elsewhere demonstrates that there is no univocal correspondence between eruptive style and Pele's hair texture.