682 SEDIMENTARY PROCESSES/Karst and Palaeokarst Figure Suffosion dolines on glacial till, formed by downwash ing of sediment into cavities in the underlying limestone Black Mountain, South Wales Many are now largely dry and were formed under different climatic regimes, reflecting either greater rainfall or the blocking of underground drainage by permafrost; Cheddar Gorge in south-west England is a fine example of the latter So-called blind valleys end abruptly downstream against an often steep slope where a surface stream sinks underground, though the former surface continuation may continue beyond at a higher level Conversely, headward excavation by a spring may form a valley ending abruptly upstream at a steep slope, called a steephead or pocket valley Emerging saturated karst waters may precipitate calcite, often under biogenic mediation, to form sometimes extensive deposits of tufa or travertine, such as those of Plitvice, Croatia Residual limestone hills at scales from a few metres to hundreds of metres high are an inevitable consequence of focused drainage from surrounding limestone, particularly where this is sufficient for turbulent flow, and the enhanced dissolution rates associated with it, to occur Although individual hills can be regarded as landforms, they are more logically considered here as elements of the largest scale of karst development, karst landscapes Large-Scale Karst (Karst Landscapes) Karst landscapes can be broadly defined as areas, typically covering many square kilometres, encompassing characteristic assemblages of karst landforms and karren Generally, though not invariably, they reflect prolonged karstification over several million years and large-scale interactions between geology, tectonics, and climate The youngest distinct type of karst landscape, characteristic of many cool temperate regions subjected to repeated glaciation during the Pleistocene, is termed glaciokarst (Figure 6) The Burren of western Ireland is a classic example and shows features typical of glaciation, such as ice-plucked Figure Temperate glaciokarst landscape with typical joint controlled clints and grikes, rinnenkarren, rillenkarren, and kamenitzas The Burren, Ireland crags, scoured rock surfaces, limestone pavements, and erratic boulders Commonly these are superimposed on pre-existing karst landforms/landscapes, but smaller scale karst landforms and karren, particularly grikes (kluftkarren), small dolines, and caves, have commonly been superimposed on the glacial landforms since the ice retreated Fluviokarst landscapes are dominated by valleys cut by surface rivers, either before significant underground drainage had developed or under different climatic conditions, notably periglacial environments, which favoured surface rather than underground drainage Many fluviokarst valleys are now largely dry because drainage has been captured underground Cone karst (Fencong) is dominated by conical or hemispherical hills, typically a few tens of metres high and several hundred metres across, separated by dolines and other irregular depressions Cone karst develops only in wet tropical climates such as in parts of Java, some Caribbean islands, and particularly in China’s Ghizou Province Tower karst (Fenglin),