Note the figures in the bottom left of the photo. The route up and down essentially takes a direct line from where they are up to the rim. The going here is a little risky as the ground is steep, composed of crumbling mud and handholds are very liable to come away in your hand. Vertical distance to cover is approx. 40 m. The crater rim itself is composed of very slippery compacted ash and should be negotiated cautiously. Detail of the route up/down can be seen
here.