In Mandarin Chinese, 土 (Pinyin: tǔ) means “earth”, “soil” or “clay”. (Also, “crude opium”.)
Earth is one of the five elements of Wǔ Xíng. There are many historical forms of this character that look very much like a lump of clay on a potter’s wheel. The modern symbol, however, is more like a scribble of a grave with a simple cross.
More photos of clay, earth, soil, and sea glass @ Shutterstock.