Extract from the Global Volcanism Program/USGS activity report:
Geologic Summary. The triangular island of Hierro is the SW-most and least studied of the Canary Islands. The massive Hierro shield volcano is truncated by a large NW-facing escarpment formed as a result of gravitational collapse of El Golfo volcano about 130,000 years ago. The steep-sided 1500-m-high scarp towers above a low lavaplatform bordering 12-km-wide El Golfo Bay, and three other large submarine landslide deposits occur to the SW and SE. Three prominent rifts oriented NW, NE, and south at 120 degree angles form prominent topographic ridges. The subaerial portion of the volcano consists of flat-lying Quaternary basaltic and trachybasaltic lava flows and tuffs capped by numerous young cinder cones and lava flows. Holocene cones and flows are found both on the outer flanks and in the El Golfo depression. Hierro contains the greatest concentration of young vents in the Canary Islands. Uncertainty surrounds the report of an historical eruption in 1793.
Source: Instituto Geográfico Nacional (IGN)
Hierro Information from the Global Volcanism Program
Some links I've discovered on the IGN pages (translate needed):
Hierro Updated Summary - various charts of eq loc and depth, accumulated energy, etc.
Earthquakes last 10 days (Canary Islands)
Seismic signals (all sites)
Latest IGN News
* I say it looks bad because of the repercussions of a slump or landslide.