Is the oven on it already?
Which wall sides or back?
Was there a footing or just a slab?
Is there a crack on the slab? (wet down the slab and watch the water it will find even the smallest crack, you will see bubbles.
A crack through block indicates serious movement.
If there are no other visible cracks clean a 1' square section of the crack with soap and water rinse well after dry paint the area with white paint or a light paint. Put register marks (black lines) on the paint on either side of the crack parallel to the crack and a couple running right across the crack horizontally. measure the parallel lines and note the measurement (exactly) the horizontal lines can me measured after they have moved. this will tell you what direction it is moving if you cannot figure it out visually.
At first guess Id say the slab on grade is cracked also, look closely
Check it and get back...don't panic it can be fixed.
