Photograph of the month

摘要

Microstructure of deep polar ice. The image shows ice from the lower, warm part of the EPICA-Dronning Maud Land (EDML) core in the Antarctic ice sheet. At a depth of 2375 m, the ca. 130.000 years old ice is at -13℃ (Ruth et al., 2007; Wilhelms et al., 2007), i.e. a homologous temperature of 0.952. Polar ice is thus a "hot material" with microstructural behaviour close to that of silicate minerals at high metamorphic grades. The image shows the c-axes distribution map (AVA) measured with the automatic fabric analyzer (G50) by Russell-Head Instruments(see also Wilson et al. 2014; Petemell et al. 2014; Faria et al., 2014a). Colour coding is according to c-axis orientation. Strong dynamic recrystallization is indicated by interlocking grains and orientation families: the bright purple grains may belong to a single grain with a highly irregular shape, making it appear as multiple grains due to sectioning effects (Urai et al., 1986).