| The
large expanses of the floor of the Caloris basin that have not been overprinted
with more recent cratering show extensive fracturing and ridging of the
surface. This material is best interpreted as flows of lava, that welled
up and filled the basin some time after its formation. Lava-filled depressions
on Earth have mixtures of fractures and ridges as those seen (albiet on
a much larger scale) on Mercury. |
 |
Many
of the ridges are compressional features where flows converged, or indicate
inflation by injection of lava below a solidified carapace, whereas the
straight-edged fractures indicate settling of the surface as the lava cooled
and contracted. |
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