Earth is one of the five flows of the True Source.
Men are historically more powerful in Earth than women.
Earth can be used to delve, or scan through earth based objects (metals, rocks, etc). It also can be used to move large amounts of earth and in extreme cases even raise mountains or create large fissures.
Strong channelers can use earth to affect tectonic plate movements creating tremors and earthquakes. Other strong channelers can again use earth to sooth such events.
Earth is also a primary ingredient in creation of power forged weaponry, but it is rare to find a blade made by that method because of the Aes Sedai's three oaths.