December 14, 2021
Little Bumps And Bigger Swells
Originally published January 30, 2012
image by Praet Marnix, Belgium
Every scene has a story to tell, we just have to find it. In this image its not Plato with its pitted floor and huge unfallen rim block, nor the hilly Imbrium Basin ejecta that magma rose through to form a sinuous rille. Look beyond to Mare Frigoris and its ridges and swollen surface. There is an explanation for the formation of concentric mare ridges in circular maria - they result from one part of the solidified pile of lavas fracturing and sliding over the adjacent part due to the whole mass having to fit into a smaller volume as the basin subsides. This explanation doesn't seem to apply to ridges such as these in Frigoris. Mare ridges probably have different origins. For example, in the center of this image it appears that a very low swell extends all the way across the narrow neck of Frigoris and littler bumps are to the east. Previous higher Sun image of the western part of this view shows a broad swell hugging the Plato side coastline. I imagine these low swells may have formed when magma or volcanic gases rose under a near surface lava flow and inflated it. We see such features on Hawaaian lava flows, but they are only meters across not 10 or more kilometers.
Chuck Wood
Technical Details
Meade 8" LX90 and the DMK 21 AU618.AS camera ,with a 3 X Meade barlow; Registax and PS.
Praet's website
Related Links
Rükl plate 4
Yesterday's LPOD: Moonwalking
Tomorrow's LPOD: Magnetic World
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