Actually, there is a larger "super cycle" going on that is every 8 years. If you notice by your chart, every 8 years we have a major correction. 1990, 1998, and now we are at the start of this one right now.
This was the first time in 20 years that that the Nasdaq has closed 6 days below the BollingerBand line. Alan Greenspan basically said last week that the housing bubble has popped. It seems fitting for a major 8 year correction to be in progress right now.