Sorry for double-posting but this one looks cooler:
/summon FallingSand ~ ~1 ~ {id:"FallingSand",Data:0b,Time:1b,TileID:51,Riding:{id:"FallingSand",Data:0b,Time:1b,TileID:51,Riding:{id:"FallingSand",Data:0b,Time:1b,TileID:51,Riding:{id:"FallingSand",Data:0b,Time:1b,TileID:51,Riding:{id:"FallingSand",Data:0b,Time:1b,TileID:51,Riding:{id:"FallingSand",Data:0b,Time:1b,TileID:51,Riding:{id:"FallingSand",Data:0b,Time:1b,TileID:51,Riding:{id:"FallingSand",Data:0b,Time:1b,TileID:51,Riding:{id:"FallingSand",Data:0b,Time:1b,Motion:[3.0d,0.4d,0.0d],TileID:51}}}}}}}}}