Topographic Constraints on the Origin of the Equatorial Ridge on Iapetus
  Saturn's moon Iapetus has an equatorial ridge system, which may be as high as 20 km, that may have formed by endogenic forces, such as tectonic and convective forces, or exogenic processes such as debris infall. We use high-resolution topographic data to conduct a topographic analysis of the ridge, which suggests a predominantly triangular morphology, with some ridge face slopes reaching 40 degrees, allowing for an exogenic formation mechanism. 
Erika Lopez Garcia, Edgard G. Rivera-Valentin, Paul M. Schenk, Noah P.   Hammond, Amy C. Barr
astro-ph.EP