Tearing ground scenery - how does one avoid this?

Can someone explain what this is an how it is caused? Scenery was generated with TerraScene (latest version) and default settings. Location was just West of the Hudson River about 20 miles south of KSWF heading south.This is not the first time this has happened to me. Mostly I see it in mountainous areas (Rocky Mountains, for example). In those cases, the "tearing" seems to flicker and appear/disappear depending on altitude, proximity, etc. In this case, this tear seemed to linger.Thanks.-DK----Fly! II v230Dell 8200 P4/1.8G, 512MB RAM, Nvidia GF4 Ti4600 v28.83, WinXP Home Edition.CH Pro Pedals and Yoke USB.