Tenerife is an island of volcanic origin and what you see above is among the remnants of an ancient caldera that preceded the present day behemoth of El Teide that itself draws so many visitors. Altitude is a concern here even at the lower levels where this photo was made for the height above sea level is more than 2000 metres. El Teide itself is more 1500 metres higher so it needs even more forethought when it comes to its exploration.
My strolling around these rocky outcrops was kept to a more relaxed level though I did stray away from them for a while. That introduced me to obsidian rocks making a glassy sound whenever they were knocked together. They are leftovers from dramatic geological activity as much as the dry arid landscape in which they are found. Vegetation survives in this harsh environment too and I was conscious of the need not to step on any of it though there was the occasional lapse. All in all, this was an incursion into an alien landscape.