Anti-lock Brakes

[Falcon1987]

I have a 98 Sierra 1/2 ton 4x4 and I was driving around in the snow today and for some reason the abs kicked in while I was braking. I had light pressure on the brake pedal, I was just easing it on and the abs kicked in.
Is this normal for driving in slippery conditions?

Also, what determines whether or not the abs kicks in?

[horse482]

ABS is activated when the vehicle speed sensor (vss) senses the wheels are locking up under braking conditions. There is a motor or pump that pulsates as you would on an older vehicle that doesn't have abs. The vss sends a signal that the wheels are locking up to the abs controler or bcm and it tells the abs pump to activate. Hope this helps.