Earth huh...? first I need to know what kind of genre your going for this one.
I can think of earth as a rumbling sound as a background to start to finish.
For melody, you can
1. try doing one going through a cave having deep echos underground (Ambient)
2. there is the earthquake pound, where the everywhere is falling apart (Heavy Rock)
3. or have fun doing one about the big, open field with a strong beat (Soft Rock)
Anyway, If none of these suit ya, you can leave me a message for other ideas. good luck
---redjkn87---
yourdaddy209
Wind aura if possible. should be something calming and building up tension. but you can surprise me iof you want tho :)