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Centre for Geobiology

More Pillow Talk!

05.07.2008 In the fresh drill core the pillow lavas show excellent fine-scale textures and subtle changes in colour that are not seen on the surface.

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In the fresh drill core the pillow lavas show excellent fine-scale textures and subtle changes in colour that are not seen on the surface. The core box illustrated here for example, tells us about heating events within the volcanic pile and perhaps also about microbes that may once have dwelt within the lavas. Read more for a description of what we are looking for in these lavas and the geological secrets they hold.

The box of core shown here contains thermally altered purplish coloured pillow basalts and their contact with an igneous intrusion called a sill. The purple colour of the pillow basalts is the result of a hot "baking effect", known to geologists as a thermal contact aureole, caused by the later intrusion of molten igneous magma into the pillow lava pile. The "uncooked" equivalent of these pillow basalts is the ideal rock type where scientists will use a microscope to look for traces of early microbial life that may have "eaten" into the glassy margins of the pillow lavas. These rocks may also provide clues to the Earth`s earliest magnetic field (see here). Lastly, the cm-scale sub-spherical "blobs" known as ocelli that are found in these pillow lavas hold information about the properties of the erupting lava and changes that the rocks have undergone due to heat, pressure and fluid flow.

Photo credit: Eugene Grosch