Symbols & Knowledge

http://www.symbols.com/symbol/144

1. The cultural origins of this symbol is from ancient Greece, where Earth is one of the four classic elements according to the Greek philosophers and scientists.
2. The knowledge portrayed is that Earth is supposed to be the heaviest of the four elements, therefore any Earth-laden substances would fall fast straight down  to the center of the cosmos. Earth is associated with sensual aspects of both life and death in later occultism.
3. This symbol can be emotive because Earth is seen to be strong and powerful, along with sensual. This symbol can also be vague because the meaning behind it would not be widely known in modern culture.
4. Some problems of knowledge with this symbol is it is very simple, therefore it is hard to derive the idea of Earth from it. Also since it is an ancient symbol, the modern culture may not know the background of this symbol and therefore not understand the meaning behind it. Also there are many other symbols for Earth so people may not know there are many symbols for Earth or they do not know all of them.
5. 
http://jaredleto-best-idol.blogspot.com/2011/08/triad-o-que-significa.html
This is a symbol that symbolizes air. This is related to Earth, because it is one of the other elements but it could easily be confused with the symbol for Earth if one does not know the symbols well. This is also as a symbol widely used by a well known bands called 30 Seconds to Mars, and they chose this symbol because it means air; but people know it more as a symbol for the band than for air.