Monymusk have been left playing a waiting game on promotion from Division 3 after this defeat by the league leaders.
The home side needed at least a point to keep their hopes alive of a place in the top six which would guarantee a place in Division 2 next season. Musk held the city side at bay for nearly an hour but then the breakthrough came for GNA and that was the catalyst for three more goals.
Monymusk will now finish the league in seventh position and, with at least one club folding during the season, are hoping that will be enough to see them go up.
Injury kept veteran central defender Phil Stewart out of the starting line-up for Monymusk and his place was taken by Andy Robertson. The home side started the game brightly with Jamie Mackie going close with a header from a corner soon after kick-off. Great Northern then had the ball in the net in 18 minutes but the referee blew for offside.
Good work by Ryan Sangster on the right gave Tony Forshaw a chance in the box on 24 minutes but a GNA defender produced a goal-saving block.
Musk had the visitors rattled now but just could not make their pressure count. The half ended with a Mackie cross just missed by Cruden.
Forshaw went close to getting the opening goal four minutes after the restart with a low drive following a free kick but the GNA keeper, who seemed to see the effort late, just got a finger tip to divert the ball for a corner. The livewrie midfielder then went on a great run down the left but again his shot was blocked by a defender.
Play was then held up as Ryan Sangster received a yellow card for his involvement in an altercation with an opposing player. This seemed to unsettle the home side and, against the run of play, Great Northern broke the deadlock in 58 minutes with a quick throw-in on the right which caught the Musk defence cold and the GNA player knocked the ball past keeper Mikey Fyffe.
Sangster was then replaced by Paul Doverty but just four minutes later GNA scored again, this time a through ball splitting the Musk defence and a player running on beat Fyffe.
Liam Beaton came on for Robertson who was struggling with an injury and Neil Duncan replaced Grant Forsyth as the home team tried to salvage something from the game. With 10 minutes remaining a great cross from Cruden gave Forshaw the best chance of the game to score but he was just wide of the target.
Two minutes later Fyffe brought off a great save and from the resultant corner the ball came back out to a GNA player who rifled a great shot high into the net to make it 3-0.
Great Northern added a fourth with minutes remaining when a player broke down the left and sent a cross over to the striker who made no mistake.
Monymusk: Fyffe, Duthie, Lyon, Robertson (Beaton), Nicolson, Forsyth (Duncan), Mackie, Forshaw, Sangster (Doverty), Harkness and Cruden. Subs: L. Barron and Moir.