One of our most remarkable walks on Tenerife was through the area known as Las Arenas Negras, to the west of Puerto de la Cruz. The last major volcanic eruption here was in 1706, and the black ash over which we walked for much of the day sparkled in the sun and crunched under our feet like a million crushed Crunchie Bars. There are trees growing in places - you can see some wonderfully green little ones to the right of the photo, beyond the line of the Canal Vergara, a covered canal about the same width as a Madeiran levada. But around the central ash desert are forests which have been recently burned, and it was amazing to see how the new growth shoots out from the charred trunks, so that the trees resemble these hilariously disguised telegraph poles and communications masts that you see on the way to Perth.
If you're interested, there are more photos of this day on Flickr - just click through on the photo here.