Protects the target with an earthen shield, reducing casting or channeling time lost when damaged by 30% and causing attacks to heal the shielded target for X. This effect can only occur once every few seconds. 9 charges. Lasts 10 minutes. Earth Shield can only be placed on one target at a time and only one Elemental Shield can be active on a target at a time.
Protects the target with an earthen shield, reducing casting or channeling time lost when damaged by 30% and causing attacks to heal the shielded target for X. This effect can only occur once every few seconds. 9 charges. Lasts 10 minutes. Earth Shield can only be placed on one target at a time and only one Elemental Shield can be active on a target at a time.
Earth Shield is a nature-based buff similar to Prayer of Mending. When getting attacked, it heals the buffed target. It can only proc every few seconds, and has nine charges. It is available in the Restoration tree.
In PvE, Earth Shield's primary use is as a highly mana efficient long-duration heal over time on the tank. It is by far your most mana efficient single target healing spell, and its reactive nature minimizes overhealing.
You generally want to keep Earth Shield on the tank in group situations, although other occasions may call for it to be placed on a caster who is being interrupted, for example in Nightbane's airborne phases when healers get targeted, or if a Warlock or Mage or Moonkin is AOEing a pack of non-elites.
Earth Shield is also great in PvP situations as it greatly increases the shaman's survivability.
Keeping Earth Shield on yourself when you do not need the healing is inadvisable, as it cannot be used together with Water Shield, thus causing you to lose out mana regeneration. Even when you are taking damage it is sometimes preferable to keep Earth Shield on someone else so that you can benefit from the extra mana from Water Shield, both the passive regeneration bonus and the mana granted by the orbs when you take damage.
Edit
Patch 4.1.0 (26-April-2011): Earth Shield healing done by Restoration shaman has been reduced by 20%. 
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Patch 2.4.0 (2008-03-25): Number of charges reduced from 10 to 6. Mana cost reduced by 50%. 
