The elemental planes represent some of the fundamental building blocks of the cosmos. The four elemental planes of air, earth, fire and water are the fount of the four elements, which are present in all things.
Where the elemental planes touch the positive and negative energy planes, they create Quasielemental Planes; mixed with positive energy they form: earth: mineral, water: steam, air: lightning, fire: radiance. Mixed with negative energy they form: earth: dust, water: salt, air: vacuum, fire: ash.
The elemental planes are inhabited by powerful elementals, as well as elemental forms of normal creatures.
The Elements in Dark Sun
In the Dark Sun cosmology, the positive and negative energy planes don't exist, so there are no quasielemental planes. In addition, the paraelements are changed: Ice is replaced with rain; smoke with sun; and ooze with silt. The paraelement of mamga remains the same.