Solar Elastosis
UV doesn't tan you, it cooks your skin's scaffolding into yellow rubber. Permanently.
Grounded in the research on Solar elastosis (Wikipedia)
What it actually is
Solar elastosis (aka actinic elastosis) is an abnormal buildup of degraded elastin in the dermis from chronic sun exposure. It's not a tan or a wrinkle, it's structural damage. The skin goes thick, leathery, yellowed and deeply furrowed. This is the literal definition of photoaging: cumulative UV, not birthdays, doing the work.
The mechanism: collagen gets replaced by junk
UV radiation hammers the dermis. Two debated paths: UV either drives fibroblasts to pump out malformed elastic material, or it degrades your existing collagen and elastin into tangled basophilic clumps. Either way healthy collagen gets swapped for disorganized elastotic masses. Under Verhoeff stain those tangled fibers go black, that's the histology signature pathologists use to confirm it.