Textured surface rotation looks horrible   

Ok, this is a little bit difficult to explain, but I'll try my best:
I create a surface in the following way:
1) I make a flat square that is built from N*N small squares.
2) Some of the vertices' height is changed randomally so it will look 
realistic.
3) Each small square recieves a grass texture.
4) Render using an index buffer.

When rendering a static picture of the surface it looks fine, but
when I use a rotation matrix and the surface is rotating around itself,
all the points seem to be 'sparkling'. No matter what speed the rotation is 
done, this problem exists. However, when its done really slow, I can notice 
that
each point on the surface changes its color a lot faster than it should be 
(lets say the surface rotated 0.1 degrees, and before the rotation I looked 
at a certain group of points (ie. 4X4 pixels) on the surface, now it looks 
totally diferent, nothing in common). Maybe this is just because of low 
quality texture rendering. If so, then how to control the quality?

date: Sun, 28 May 2006 06:00:02 -0700   author:   Uri_G