History H/W.Says the Sphinx eroded more in last 50 yrs than in the last 50 centuries.Can u pls tell me why?

Question

I got History homework. It says that the Sphinx (in Egypt) has eroded more in the last 50 years than in the last 50 centuries. Why has this happened? Pls tell me ASAP.

Answer 1

Air pollution, human contact and, oddly enough, moisture. Earlier attempts at preservation sealed the surface so the soil moisture wicking up from below has been trapping salts under the surface layers.The salts cause the stones to break (spall) and fall off. This plus the acids in the atmosphere has been rotting the stone.

here is a decent reference link.
http://www.touregypt.net/featurestories/sphinx2.htm

Answer 2

Unfortunately you get a lot of this from scientists/historians - I think they are all just trying to get into National Geographic or published in general - the question I would pose back to these experts is "how do we know how much it eroded in any 50 year period to make this comparison", "for instance how do we know how much it eroded from say 950 to 1000 AD to compare the last 50 years to"
These are the same folks that in the 70's told us we were entering an ice age that now say we are facing global warming. Both of these professions have been degraded by the need to be published and lack of critical thinking