Seismic sense

"earth"

- I see with earthbending. It's kind of like seeing with my feet. I feel the vibrations in the earth, and I can see where everything is. You, that tree... even those ants.



Seismic sense is a sub-skill of earthbending that constitutes for physical sense. This skill enables earthbenders to detect vibrations in the ground to perceive objects, people, and other aspects of their environment, essentially acting as sonar, but through the earth.

History
As the badgermoles were the original earthbenders, they were also the first users of seismic sense. Naturally blind, these creatures used this ability to navigate their dark world.

The blind Toph Beifong was the first known human practitioner of this technique, developing the sense at a young age by learning from the badgermoles and using it to perfect a style of earthbending different than the normal one. Later, she perfected her seismic sense to such an advanced degree that she could detect the slightest of changes in movement, thus using the skill as her method to explore the world, and developing a technique that serves as a way of lie detection. This heightened sense of awareness is at the foundation of metalbending, as Toph's sense allowed her to feel the unpurified earth materials that were still present in the metal.



The second known human practitioner of seismic sense was Avatar Aang. Taught by Toph, he was fully capable of using the sense to perceive objects and movement out of his line of vision or while blindfolded. Due to this skill, Aang was able to detect Ozai's attempt to strike him in the back during the Battle at Wulong Forest.

Toph later passed this skill on to her daughter, Lin Beifong, who put it to use in her job as Chief of Police to find hidden locations, such as an Equalist factory operating underneath the Sato estate.

Usage
The first and foremost of seismic sense's applications is the ability to perceive surroundings. By sensing vibrations in the ground, earthbenders can perceive their surroundings as precisely as normal sight, and in some cases with even greater clarity. The advantage of the sense over normal sight is that practitioners are able to pick up things that are barely visible or even imperceptible to the naked eye as well as things out of their line of sight. Obstacles that would normally obstruct regular vision, such as walls and thick dust clouds, are rendered ineffective against seismic sense. Seismic sense does not only provide surface vision, as the vibrations also travel underground, enabling the user to effectively detect caverns and other deep subterranean cavities.

Metalbending


Notably, seismic sense allowed for the discovery of the art of metalbending. The ability allows an earthbender to pick up on the minute pieces of unpurified earth still present in the metal. Locking on to the pieces, an earthbender can bend the earth and thus the metal.

Lie detection
Since humans have a physical reaction when they lie, such as a heightened heart rate, earthbenders who have perfected this skill are able to lock on to those physiological changes and tell whether or not a person is lying. However, these reactions can be suppressed by individuals with great control over their emotions, such as Azula, rendering even the most skilled seismic sense practitioner unable to tell if a statement is a lie.

Limitations
Seismic sense is not without its limitations. The practitioner must always be in direct contact with solid ground to use the sense at all and the ability only detects things in contact with the ground or made of earthen materials; non-earthen objects floating in water or thrown into the air are undetectable, unless by extrapolation from the detected positions of one's opponents. If the user is in the air or water, or even standing on a non-earth solid such as ice, the bender will be unable to sense anything through that substance.

Sand, although an earth-based substance, is not firm like normal earth, and renders seismic sense "fuzzy" and very imprecise for earthbenders who are not used to bending it. Uninterrupted contact with the ground is preferred for the user - an object such as a shoe sole interferes with the sense. Lie detection is not possible on a sandy surface, as Toph could not detect if Ghashiun was lying about stealing Appa. Although allowing the user to detect their surroundings into detail, the sense does not allow for perception of facial features  or written characters.

Known users

 * Badgermoles
 * Toph Beifong
 * Avatar Aang
 * Lin Beifong