Uppon seeing his sensei emerging from the ground, Yugi got surprised...
-Sensei!!! you almost gave me a heart attack! geez... Are you... are you alright? need some water? [draws a glass from his sack, and fills it with some water, with the suiton no jutsu.]
-There you are sensei... don't die on me!
(as Sensei drinks the water, Yugi answers the question)
-Earth chakra is used to manipulate already existing earth, by channeling it in the earth bellow our feet and infusing it with the earth we want to control/manipulate. We can also create earth out of earth chakra, which is already infused with our chakra, and manipulate it as well. It's special characteristics is solid and dry.
Earth is strong against water, as it absorbs it. It is however weak against lighting, as the lighting's vibration destroys earth, and lighting chakra can dispatch infused chakra in the earth easily. Strong fire can melt earth to make lava.