Shield of Sand

A technique that is unique to Gaara. Whenever Gaara is about to be harmed, a shield of sand will automatically surround and protect him. The sand will react regardless of Gaara's will, even protecting him from self-inflicted injuries. This automated self-defense was given to him by his mother Karura who, before her death, imbued her chakra into his sand through her sheer strength of will to protect her son.

Overview
The defensive power and versatility of the sand is where this ability truly shines. In Part I, the shield was formidable in both speed and strength — capable of withstanding considerably strong attacks and blocking fast projectiles. However, it could be defeated with extreme speeds and a great amount of brute force, as was the case with Rock Lee's Reverse Lotus. Later, in Part II, Gaara's sand shield became so fast that even Amaterasu, whose flames are generated instantaneously, failed to breach it, and his sand shield became so strong that the extreme force of the Fourth Raikage's Guillotine Drop failed to crush through it. The Shield of Sand and the Armour of Sand together were known as Gaara's, well known and praised by even Naruto Uzumaki, who had just witnessed the Third Raikage's defences. Even the Fourth Kazekage noted that it was possibly because of this technique (in reference to Karura), that it was possible that Gaara was able to be Kazekage at such a young age.

Gaara can also change the shape of the shield and its density, to increase both speed and defence. The more powerful variations of the shield is that of the Sand Sphere, the Shukaku's Shield and the form of his mother. Whenever one form of this defence is breached, Gaara has been shown to improve and create other more powerful defences. Gaara can completely surround himself in the shield to further increase his defensive capabilities. He then uses the Third Eye to watch his opponents' movements and control sand as necessary to battle them. In addition to being extremely dense, this sand-sphere can form spikes from its surface to spear any would-be attacker. This formation can be used in mid-air. In Part I, Gaara can use this technique to shield himself from his opponent long enough to perform his transformation into Shukaku, though with sufficient force, this defence can be breached.

After the Fourth Great Shinobi War, Gaara is able to incorporate his other abilities, such as Wind Release and his kekkei genkai into his shields. Mixing his unique sparkling metal particles into his Shield of Sand, he was able to create a complex and powerful defence; able to completely guard against jutsu specifically designed to exploit his sand's weaknesses.

Trivia

 * This ability was first believed to be enacted by Shukaku's desire to survive but even after the beast was extracted from Gaara's body, the ability remained with him. Both Gaara's father and uncle have stated that it is his mother's will that moves the sand to protect her son out of love and not Shukaku's desire.
 * In Gaara Hiden: A Sandstorm Mirage, it was stated that this technique could be used infinitely, since it requires no chakra from Gaara; and was described somewhat as a "living thing", since it utilises Karura's chakra instead.