1. The Solution Process
Main reaction:
CaCO3 + H2O + CO2 = Ca+2 + 2HCO3-
2. Factors Controlling the Solution Rate
a. amount dissolved CO2
partial pressure of CO2 in air: as the PCO2 increasese, the quantity of CO2 absorbed by water increases
temperature: cooler water is capable of dissolving more CO2 that warmer water at a given PCO2
biological processes: decaying humus is an important source of CO2
b. climate
temperature, precipitation, biological activity
runoff generation is the most important effect of climate
1. Lithology and structure - ideal conditions for a fully developed karst landscape requires limestone that is:
a. fairly pure (over 60% calcite for some karst; over 90% calcite for fully developed karst landscape)
b. very thick
c. mechanically strong
d. massively jointed
2. Porosity and permeability
a. porosity: percentage of pore spaces in a given volume of rock or soil
primary porosity: intergranular voids
affected by:
grain size distribution
particle shape
degree of packing
secondary porosity: voids due to joints, faults, fratures or bedding planes
promotes circulation by increasing permeability
porosity is important only if rocks are also permeable
b. permeability: ease with which rock or soil transmits water
1. Surface Drainage - dry valleys and disrupted surface drainage
2. Subsurface Drainage
a. Model 1
vadose zone (zone of aeration)
phreatic zone (zone of saturation)
water table reflects overlying topography
diffuse aquifers
groundwater flow follows Darcy's Law:
V = volumetric flow rate
h = head
L = distance between 2 measurement
points
K = hydraulic conductivity
Q = discharge
K = hydraulic conductivity
I = hydraulic gradient
A = cross-sectional areab. Model 2
no water table
collection of conduits that function like a 3-dimensional river system
conduit aquifers
groundwater flow determined by gravity; may be turbulent
1. Dolines (sinkholes)
2. Uvala
3. Poljes
4. Karst valleys
5. Cockpit & tower karst
6. Caves
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©
K.A. Lemke (klemke@uwsp.edu)
Last modified October 19, 2002 |
