normal rendering v terrain rendering?

Hi, I've got this problem. I have exported a terrain like a normal model file and openGL is rendering it wrongly. Here are some screenshots. Terrain A close up all I did here was to switch the terrain data file with the model data file Is it because of GL_TRIANGLE_FAN which I am using? Or is it that there is a difference in code to render models and landscapes? Or did I export the terrain wrongly? Thanks.