  We present a two-dimensional system which exhibits features of self-organized
criticality. The avalanches which occur on the surface of a pile of rice are
found to exhibit finite size scaling in their probability distribution. The
critical exponents are $\tau$ = 1.21(2) for the avalanche size distribution and
$D$ = 1.99(2) for the cut-off size. Furthermore the geometry of the avalanches
is studied leading to a fractal dimension of the active sites of $d_B$ =
1.58(2). Using a set of scaling relations, we can calculate the roughness
exponent $\alpha = D - d_B$ = 0.41(3) and the dynamic exponent $z = D(2 -
\tau)$ = 1.56(8). This result is compared with that obtained from a power
spectrum analysis of the surface roughness, which yields $\alpha$ = 0.42(3) and
$z$ = 1.5(1) in excellent agreement with those obtained from the scaling
relations.
