A ripple effect is a situation where, like the ever expanding ripples across water when an object is dropped into it, an effect from an initial state can be followed outwards incrementally.
In sociology, it can be observed how social interactions can affect situations not directly related to the initial interaction, and in charitable activities where information can be disseminated and passed from community to community to broaden its impact.
See also 
- The Economic Ripple Effect Gone Awry.
- Development sociology By Norman Long, Routledge ISBN 978-0-415-23536-5
- Experience needed to make VSO's 'ripple effect' work The Guardian 17 September 2004.
- Black, Sue (2001). "Computing ripple effect for software maintenance". Journal of Software Maintenance and Evolution: Research and Practice 13 (4): 263–279. doi:10.1002/smr.233. ISSN 1532-060X.