ruIniforme - S'applique à des reliefs évoquant des ruines (morphologie assez fréquente des pays karstiques). [Dict. de géologie, Foucault/Raoult].

ruine ... ruIniforme (v.1800) . Géogr. Se dit de rochers ou de reliefs tourmentés, à l'aspect de ruines, résultant d'une inégale météorisation des roches hétérogènes [Dict. Larousse Lexis]

So, CHAOTIC, maybe? Or JAGGED?

The ground between the lakes resembles Gruyere cheese, being riddled with large rifts, caves and chambers hollowed out by the underground waters. The greatest concentration of swallow holes is to the east of the entrance to the Cong Canal: here the rocks form a ****chaotic landscape**** of hollows and tilted blocks where collapses have taken place into the caves beneath.
[http://www.gsi.ie/workgsi/groundwater/karstbook/07-western-l...]

Divers have explored the spring down to a depth of 90 m. Beyond an underground chaotic zone, close to the outlet, they discovered a single, quite straight karstic gallery at a depth of between 35 and 110 m
[www.zrc-sazu.si/izrk/carsologica/ Acta291/Pdf291/arfib.pdf]

We arrive at a plain that is almost totally devoid of vegetation taking the left-hand arête to reach the summit through a chaotic mass of greyish limestone rocks. Once we are on top of El Reloj (1,535m high) we will go around it and after crossing its summit we will drop down to a slope, full of potholes and blocks of stone, inside a closed valley through which we reach the arête that will take us to the Simancón at a height of 1,561m
[http://www.sol.com/en/modulo.asp?IdContenido=1037&IdProvinci...]

in coastal lowlands where saltwater intrusion is extensive, the mixing of meteoric water with saline water in the epikarst results in an extremely jagged and fretted rock surface (Fig. 2). In the Bahamas, such surfaces are called "moonrock" (Davis and Johnson, 1989) because of the cratered and chaotic appearance of the rock surface.
[genet-server.ibtm.tuwien.ac.at/ speleo/art/Sg2/SG2_artId21.pdf]

Formed of karstic limestone, the Aladag Range presents a jagged, intimidating and forbidding appearance, which changes, each new morning and each day’s end, to a seductive warmth, when the sun’s rays touch the lifeless stone and paint its golden-red image onto the peaks
[http://www.outdoorneophyte.com/Turkey.htm]

Raised coral platform with slight depression in centre, 15 m coastal cliffs, generally undercut, karstic surface with steep-sided pits and jagged limestone pinnacles around margin, reef rubble in centre; 3 beaches to north, north-west and north-east
[http://islands.unep.ch/IKV.htm]

The Krka River, which follows a very irregular channel through jagged karstic terrain, is the principal feature of Sibenik's hinterland. It is interrupted here and there by waterfalls and rapids, and marks the border between northern and central Dalmatia
[http://www.europeanvacationguide.com/KrkaNatlPark1216_Overvi...]


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Note added at 5 hrs 59 mins (2004-04-07 00:00:31 GMT)
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Assuming it is NOT in fact RUNIFORME: \"Dont la forme rappelle celle des runes\".
\"Rune. Caractère des plus anciens alphabets germaniques ... Les runes sont caractérisés par des traits surtout verticaux\". [Lexis]

So maybe \"jagged\", or even \"pinnacled\".