The cliffs on each side form part of Los Gigantes and, as we were told, are really the inside of the mountains of lava after the outer layers have fallen away. To be honest, they are very impressive. They rise upwards from the depths of the sea and form an impressive outline against the sky.
It's possible to see the lava chimneys where the hot lava was pushed upwards from the volcano. They look like white water marks against the black rock. But the lava always goes up, cooling as it reaches the top of the chimneys and then being overtaken by more hot lava rising behind. This is how the different layers are formed.
The lighter brown colour is fossilised earth that has formed on the surface after an eruption and been trapped after the volcano has erupted again. You can appreciate the size of Los Gigantes if you look at the last photo, in the bottom right-hand corner is a canoe!