My thanks to David Benzing, husband of Linda Grashoff, for venturing to explain what process is on display in the third and fourth photos from the bottom. As David writes: “My best guess is road salt (likely died blue) has dissolved against the inside of the wood containment as moisture penetrated in from outside. The laminations visible correspond to growth rings in the wood, each of which—owing to the varying sizes of the water-conducting cells present in each ring—allowed the salt water to move across the planks unevenly from inside to outside. It looks like the patch of wood with salt crystals on it was either unusually permeable to moisture, or that surface was somehow exposed to more moisture than the surrounding areas.”
It’s hard to tell from the photos but some of the white and bluish areas were an inch or two thick in places with the consistency of a bar of soap.