convection cells

Crystalline dancer

Nature sculpted a fine shaped cluster inside a geode from Artigas in Uruguay, source of some of the world’s finest purple quartzes. The crystals grew in gas bubbles in the Parana flood basalts that cover vast swathes of northern Uruguay and Argentina along with Southern Brazil.

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Aurorae shimmering over the steaming Earth

Geysers and hot springs occur when water gets superheated by underlying magma chambers filled with molten rock. A convection cell of sinking rainwater and rising superheated H2O establishes itself, dissolving and redepositing minerals as it cycles up and down through the energy gradient. Like the glowing plasma above which is fuelled by charged particles fired off from the sun interacting with our magnetic field and the particles at the tenuous edge of the atmosphere, the energy source is removed from the visible effect, but both reveal the essential interpenetration of all things and energies that make up the beautiful universe (or multiverse) that we live in.


Image credit: Iurie Beligurshi

Lovely geode

These balls of quartzy rock record the shape of bubbles in long frozen basaltic lava. They were deposited after the flow had cooled by silica rich waters, possibly driven in a convection cell by the heat of cooling lava. What I love about them is the element of surprise; no one knows what marvellous landscapes hide within until the diamond tipped saw is sent a whirring. In the lovely example in the photo (sorry no scale available) layers of agate started to fill the ex bubble from the outside in. A layer of jelly like colloidal silica probably precipitated to create the horizontal banding, while crystals of lovely pink chalcedony (coloured by traces of iron oxide or manganese) and drusy points of water clear quartz grew inwards into the cavity.


Image credit: Captain Tenneal