Updated 5th November 2003; 21st February 2016; 24th April, 2nd May, 17th September, 23rd November 2024

   A resurgence in the large Hoyo Frio depression. A wet crawl reaches a sump after 30m but a bypass can be entered 13m back on the right. The passage eventually becomes too low in water.
During an optical brightener test from site 3884, detectors were placed here from 13th February 2016 and checked over the next few days in rising and falling flood conditions. The results were consistently negative. The optical brightener came through at the Jivero 1 resurgence after 48 hours. (The full details can be found here.)
   Over a 4-day test, October / November 2024, OBA injected just below the resurgence into the Selvijo entrance depression was traced to Loca 1 and to a passage in Selvijo, at around station 24-02.56. More details can be found here.)

   The resurgence was re-explored at Easter 2024 with the probability that new passage was entered (sketch below) - the following account is edited from the logbook:
   Ignoring the bypass, the explorers went through the so-called sump which was a duck. This led into a series of challenging squeezes and right-hand corners in water until after a small chamber a final left-hand turn was too tight to pass. Hard going!
    We went back and took the bypass mentioned in the description, there's a good draft here. After some sandy crawls we found the upstream end of the corner we could not pass. The passage from there was walking for a short bit before it got low and wet. Already soaked we pushed through and, after another small standing height chamber and another low and wet bit, we entered a very large passage / chamber (Flan Caliente) about 10m high, 5m across at the widest and 20m long (estimates). Not realising this was potentially new stuff we looked at muddy floor level passage that dropped to a low crawl after 30m, continues, We then looked at a high level sandy passage and at this point being high up and undisturbed we realised we were probably in new stuff so did not push it further. However, there's no strong draughts but lots of passages to choose from going off this chamber.

   Water is assumed to come from Cueva del Selvijo (0028): The following comment was made after an Easter 2024 push downstream in Selvijo, "an angular passage that was of almost identical character to the streamway in Loca I." However, with the resurgence being surveyed 3m higher than the one downstream outlet seen or investigated in Selvijo, it may be that this Selvijo stream flows below the resurgence into Cueva de la Loca 2, #0020

References: Fernández Gutiérrez et al, 1966 (survey); anon., 1975b (Easter and summer logbooks); Kendal Caving Club and Manchester University Speleological Society, 1975 (survey); Cox G, 1973; Manchester University Speleological Society, 1982 (survey); Mills L D J and Waltham A C, 1981 (survey); Corrin J S and Smith P, 1981; anon., 2016a (January, February logbook); anon., 2024b (Easter logbook); anon., 2024d (summer logbook); anon., 2024e (autumn logbook)
Entrance pictures : Easter 2024 : August 2024 - including 360° photos
Underground picture(s): Easter 2024 : August 2024
Video: New passage Easter 2024 (YouTube) : decorated top level, summer 2024 (YouTube)
Detailed Survey : from 1975: low res  high res : sketch after Easter 2024 exploration : summer 2024, to appear with 0028 survey
Line Survey :
On area survey : 1975 Ozana area map. Not a lot of detail. low res  high res
Survex file : August 2024 : overlapping with 0028, also shows Loca 2