I wish I could favorite one piece more than one time, cause this piece of art is amazing. The atmosphere you suggested through the color scheme and coloring is brilliant, I love the lineart as well, and Korra's grim, focused expression and hair. Fantastic work, you're a great artist!
Earth-bending with water-bending techniques. It's liquid rock. Just like lightning-bending requires water-bending techniques to let the energy "flow" through you. Use fire-bending to control any spontaneous combustion brought on by the heat, and air-bending to make sure the convection doesn't kill you. So, yeah. Avatar-only.