Water > Fire = Water Douses Fire
Fire > Wind = Fanning the flames
Wind > Lightning = Air is a poor electrical conductor
Lightning > Earth = Earth is made of elements ("metals") which conduct electricity. On a different aspect, let's take a look at the nature of both chakras. Earth jutsu are fairly straight forward - they make solid structure, or deal with the creation of earth into different forms. Lightning in the Naruto universe represents energy, and it is explicitly demonstrated with vibrations. If you take atoms, the building blocks of any structure (represented by Earth) and increase their energy, they start to move away from each other; that is earth is torn apart by the application of energy. It makes sense from a molecular stand point. And on a bigger scale it works as well. If I had a giant boulder and could cause it to vibrate at extremely high speeds, it would shatter. Further more, from an electrical stand point, earth does conduct electricity - that's why we have lightning.
Earth > Water = the land stops the ocean.
