Dozens gathered at City Hall on Saturday to mark Earth Hour by attending environmental charity Greenrock’s Earth Hour Expo.The free community event started at 5pm and featured environmental documentaries and family friendly entertainment on the City Hall steps.And many in Bermuda joined others around the world in turning off their lights from 8.30 to 9.30pm in what has become the world’s biggest single environmental action.About 130 countries are believed to participate in Earth Hour, an annual event started in 2007.At City Hall, power generating bikes provided by the Island’s electricity utility were used to power LED lights.