part of terrain vanishes in scene view

all i did was create a new project and a new terrain... it cuts off parts. whn i change the angle of the view eather more gets cut off or i can see it all if i move it around same thing hapens. it is like it is inside a box that cuts the sides off. now it is hapening to all my projects...

Terrain problem

If you click the terrain in your project window, in the inspector window there should be several buttons. Some are to raise hight, others are for trees/grass etcetera. The button most to the right is settings. Check that out. :)