Canada
Karst ------------------
Karst is a landscape characterized by the presence of
sinkholes, caves, and underground drainage systems. It
forms when the soluble rocks, such as limestone and
dolomite, are exposed to the chemical and physical
processes that dissolve the rock, causing it to erode and
form unique landforms.
The main processes that contribute to karst formation
include chemical weathering, physical weathering, and
groundwater flow. Chemical weathering involves dissolution
of the rock due to the reaction with water and carbon
dioxide, which creates a weak acidic
solution. Physical weathering is the result
of physical forces such as freezing and
thawing, as well as the mechanical action
of water on the rock. Groundwater flow
helps to transport the dissolved rock and
contribute to the development of
underground drainage systems and
caves.
Over time,
the
process of
karstification can result in the formation of distinctive karst features,
such as sinkholes, cliffs, towers, and disappearing streams. These
features are unique to karst landscapes and provide important
habitat and resources for a variety of plants and animals.
How Karst is Formed
The process of karst formation involves what is referred to as the
“carbon dioxide cascade." As rain falls through the atmosphere,
the droplets pick up
CO
2
. Once the rain
hits the ground, it
percolates through
the soil, picking up
more CO
2
to form a
weak carbonic acid solution:
H
2
O+CO
2
= H
2
CO
3
.
The infiltrating water naturally exploits any cracks or
crevices in the rock. Over long periods, with a
continuous supply of CO
2
-enriched water, the
carbonate bedrock begins to dissolve.
Openings in the bedrock gradually increase in size,
forming an underground drainage system, allowing
more water to pass, further accelerating the
formation of karst. As these conduits grow, they may
carry insoluble rocks which scour and further
enlarge the passages.
Eventually this leads to the development of
subsurface caves. There are many definitions of
what constitutes a “cave”, but a caver’s operational
definition is that it be large enough for a human to
explore.
I
Karst
Doug Stern
Pat Shaw
Image source BC Forest Service
