In the Volcano stage there are 12 playable levels. Each one is increasingly more difficult than the next.
To get through this level;
At the start don't concern yourself with the bubbles in the top right hand corner.
Aim to pop the bubble layers that sit along the top of the long straight horozontal line of gray barrier bubbles, starting with the bubbles that sit the closest to the right hand side.
Your aim is to score the most amazing bubble hit, after you clear the layers of bubbles that cover the group of bubbles that sit in the 'bowl' shaped area of the gray barricade. Send down the colored bubble required into that bowl shape and the whole horozontal barricade drops off.