GOOG why the google stocks have decreased by 50 percents ?

When we look the recent crackdown of google, which value cours in GOOG action cotated at the Nasdaq 28 March at 1120.150$ lost 50 percents and finally founds 543.140$ on the 4th April 2014. we can explain this dilution by a spin off GOOGL

Spin off Date 04/03/2014
Security Type Equities
Parent Company Symbol GOOGL
Parent Company Price Per Share $1,135.10
New Company Security Type Equities
New Company Symbol GOOG
Percent of Cost Allocated 0.499229 (Not the Final Number)
Allocate Value the Same as Cost Basis Unchecked
New Company Price per Share $569.85
Share Distribution Ratio 1.0
Conversion Price for Cash in Lieu For Fractional Shares N/A