Petrichor is actually the smell of earth after rain.??=p
Whenever soil gets so dry plants release an oil which inhibits growth (thereby reducing the need for water).??This oil is absorbed into surrounding soils, clays and rocks.??When it rains the oil is released into the air along with geosmin which produces the smell we all attribute to rain.??
Geosmin, btw, is a compound produced by several microbes which smells and tastes "earthy".??It's what you smell when you turn dirt!??:D
Yes, I Googled geosmin.??I already knew what petrichor was; I just forgot what geosmin was called.??xp
Making you feel like a genius since 1998.