Let's create the volcanoes, using the pen tool ( P ) make this mountain shape, then use brown to orange linear gradient, using the gradient tool ( G ) adjust it making only part of the top orange. Again, using the pen tool ( P ) make the lava exploding out of the vulcano, add a strong red gradient to it. Duplicate the lava using the selection tool ( V ) + alt and go to Effect > Blur > Gaussian Blur and set radius to 20 pixels. Then, just duplicate the whole vulcano, resize and place it on the other size.