Forgive my ignorance, I am learning about topics like the geoid, geoid anomalies, gravity anomalies as it relates to lithospheric composition. In my studies, I repeatedly find talk of show wavelengths and long wavelengths having different effects on crustal composition. One example I can give that is at the focal point: Lithosphere can support short wavelength, but cannot support high wave length. What does this mean? Short wavelengths do not depress the lithosphere, long wavelengths result in flexure and a depression of the Moho. I guess, my question is why are we talking of wavelengths here?