What would likely cause an inscription on a marble gravestone to become more difficult to read over time?

the supermassive black hole is in the middle of the galaxy.

thrombocytopenia, which is a deficiency in blood platelets, can cause bleeding and bruising in the dermis similar to senile purpura. other possible causes include: exposure to ultraviolet rays and aging skin are common causes of senile purpura. senile purpura may also be a sign of collagen loss in the skin and bones.

not sure if this what   you'r looking for would be percent composition