HOME	Erosional Processes: Karst "Karst" is a German word referring to geological landforms shaped by the dissolution (ie. dissolving), by mildly acidic water, of weakly soluble bedrock - usually limestone (calcium carbonate) or dolomite (calcium magnesium carbonate). A karst formation [in this case, a "limestone pavement"] at Middle White Rocks, Flowers Cove. Michael Burzynski and the Green Team. 2002. Photo: Dulcie House. [CLICK image to enlarge.] How Karst Forms: Atmospheric water vapor readily dissolves carbon dioxide. Thus, rain contains a certain amount of carbonic acid. Carbonic acid dissolves limestone and dolomite (dolomite being somewhat more resistant). Additional acidic water, running-off from surrounding acid soils, or percolating vertically from a thin vegetated overburden, may further contribute to the general dissolution process. Thin, vegetated overburden, on "limestone" bedrock. Middle White Rocks, Flowers Cove. 2008. Photo: Susan Maunder. [CLICK image to enlarge.] Initially, surface, or near-surface, "limestone" bedrock begins to dissolve along fracture lines (or bedding planes). These fracture lines gradually widen over time, as the surrounding bedrock progressively dissolves. Eventually, DEEPER IN THE GROUND, a complex water drainage system develops, as the result of the continued dissolution of subsurface "limestone" rock. Karst is a THREE-DIMENSIONAL phenomenon! Much of it is hidden from view. The Age of Our Karst: On our Newfoundland "limestone barrens", most, if not all, examples of karst are thought to be post-glacial. That means that they are probably no older than about ten to twelve thousand years old. However, since karst formation is an ongoing process, many of the smaller and more subtle karst features are actually quite young. Limestone Pavements: Limestone pavements are found on the Great Northern Peninsula, the Port au Port Peninsula, and near Gallants south of Corner Brook. The development of limestone pavement begins in areas where glacial action has scraped all or most of the soil overburden off horizontally-bedded limestone and dolomite. Flat-topped Pavement Exposed since the glacial ice receded. The blocks, called "clints", typically have squarish edges. The intervening crevices called "grikes" [or "grykes"], can be quite deep. Flat-topped Limestone Pavement. Lower "White Rocks", Flowers Cove. 2002. Photo: John E. Maunder. [CLICK image to enlarge.] "Grikes" typically shelter a rich flora that is typical of less exposed, and often more southerly, climes. The plants shown here are [left] Laurentian Fragile Fern (Cystopteris laurentiana), [right] Hairy Willow (Salix vestita), and [bottom] Naked Mitrewort (Mitella nuda). Middle "White Rocks", Flowers Cove. Photo: John E. Maunder. [CLICK image to enlarge.] "Grikey! This one's DEEP!" Flat-topped Limestone Pavement. Middle "White Rocks", Flowers Cove. John Maunder, your humble webmaster. 2008. Photo: Susan Maunder. [CLICK image to enlarge.] Rounded Pavement Originally covered with a thin, vegetated overburden, which has subsequently washed or eroded away. Thus, the original erosional process began within the soil. The blocks typically have rounded edges, and may be more complexly arranged. Rounded Limestone Pavement. Cape Norman. 2005. Photo: John E. Maunder. [CLICK image to enlarge.] Rounded Limestone Pavement. Cape Norman. 2001. Henry Mann searching "sandy pans" for Barrens Willow (Salix jejuna). Photo: Nathalie Djan-Chékar. [CLICK image to enlarge.] Close Jointed Pavement Close Jointed Limestone Pavement. Burnt Cape. Photo: Pat/Dan Montague. [CLICK image to enlarge.] Smaller Erosional Features: Relatively flat, exposed surfaces, are usually indented by smaller solutional forms such as pits, solution depressions, linear grooves, and sinuous runnels. Pits The Beautiful Willow (Salix glauca var. callicarpaea) growing on pitted "limestone". New Ferrole Lighthouse. Photo: Pat Montague. [CLICK image to enlarge.] Solution Depressions Shallow Solution Depression. Vegetated with mosses and Poa grass. Middle White Rocks, Flowers Cove. 2008. Photo: Susan Maunder. [CLICK image to enlarge.] Drainage Features over Karst: Water that accumulates on soils that overlie "subsurface karst" [think "underground limestone pavement"!] readily drains downward, through subsurface "grikes", into the underground drainage systems so typical of karst areas. The finer soil particles, and pebbles originally lying above the subsurface grikes, have long since been carried down with the descending water, leaving a pattern of "clean" gravels and rocks, looking, at least superficially, like the borders of co-occurring "frost circles". Temporary pool on "limestone" gravels, over karst. Port au Choix. Note the dark stone tracks indicating karst-related drainage channels underneath. Photo: Pat Montague. [CLICK image to enlarge.] The same temporary pool as above [but, a different view of it], after the water has drained away. Note the "clean rocks" remaining above the underground drainage channels. Port au Choix. Photo: John E. Maunder. [CLICK image to enlarge.] A track of "clean rocks" above a subsurface drainage channel, in a dried-up temporary pond over karst. Road between St. Anthony Airport and Main Brook. Photo: John E. Maunder. [CLICK image to enlarge.] Underground Streams and Caves: The underground drainage systems of karst areas. As they continue to enlarge, such underground streams and caves often collapse, causing sinuous depressions, and even dangerous chasms and sink holes] Burnt Cape, south of the "Big Oven" sea cave. A typical karst landscape. The curving, vegetated gully, coursing toward the lower right corner of the image, especially the included steep-sided chasm near the edge of the image, is an clear indicator of a collapsed underground stream. Photo: Pat Montague. [CLICK image to enlarge.] General Reference: Karolyi (1978). [Page last updated: November 12, 2021]