Limestone Pavement Breakdown
These are flat areas of limestone blocks resembling paving stones. These
stones stand up called clints, and in between each clint (stone) there are
grooves (cracks) called grykes. This block appearance is due to 2 key reasons.
Firstly, there is the geology & structure of the rock. Limestone is a
sedimentary rock, which has many vertical & horizontal cracks in it. The
vertical cracks are called joints and the horizontal cracks are called bedding
planes. These cracks help to form natural blocks of limestone and allow water
to drain through the limestone, meaning it is a permeable rock.
A second factor is down to a process called solution (also called carbonation),
which is a type of chemical weathering. This process is when carbonic acid runs
over the surface of the limestone creating a chemical reaction between the
limestone and the acid takes place, which dissolves the rock. This means the
clints (blocks) get smaller as their sides are dissolved and so the grykes
(cracks) in between get larger. This process gives the pavement a block like
appearance.
As this takes place there is another change affecting the clint. The carbonic
acid running over the top and down the side of the clint dissolves little grooves
in the clint. These runnels (grooves) are called Karren. The clint also become
rounder over time due to his solution and its hard angular edges are rounded
into small clints called Rund Karren.
Clints (blocks)
Grykes (deep grooves)
Rund Karren (rounded blocks)
Karren (shallow grooves on clints)
The solution takes place down to chemistry. Rain water mixes with carbon
dioxide from natural (volcanoes) & human (factories) sources to form carbonic
acid also known as acid rain. When it falls on the limestone, (Calcium Carbonate
chemical formula CaCO3) it dissolves it to form calcite (called Calcium Hydrogen
Carbonate).
H2 O
Water
+
CO2
Carbon
Dioxide
=
H2CO3
Carbonic
Acid
+
CaCO3
Calcium
Carbonate
=
H2CO3
Carbonic
Acid
Ca(HCO3)2
Calcium Hydrogen
Carbonate
The actual solution of the limestone, actually first takes place when it is
covered by soil, thousands of years ago. The carbonic acid develops as rain
water drains into the soil and combines with CO2, given off by rotting
vegetation. The soil is then often scraped off by a moving glacier exposing the
pavement to further solution as we have mentioned already.
Limestone Pavement Sheets
Appearance Part 1
These are flat areas of limestone blocks resembling paving stones. These
stones stand up called clints, and in between each clint (stone) there are
grooves (cracks) called grykes. This block appearance is due to 2 key reasons.
One reason is the geology & structure of the rock. Limestone is a sedimentary
rock, which has many vertical & horizontal cracks in it. The vertical cracks are
called joints and the horizontal cracks are called bedding planes. These cracks
help to form natural blocks of limestone and allow water to drain through the
limestone, meaning it is a permeable rock.
Limestone Pavemment
Clints (blocks)
Grykes (deep grooves)
Appearance Part 2
These are flat areas of limestone blocks resembling paving stones. These
stones stand up called clints, and in between each clint (stone) there are
grooves (cracks) called grykes. This block appearance is due to 2 key reasons.
One reason is down to a process called solution (also called carbonation), which
is a type of chemical weathering. This process is when carbonic acid runs over
the surface of the limestone creating. A chemical reaction between the
limestone and the acid takes place, which dissolves the rock. This means the
clints (blocks) get smaller as their sides are dissolved and so the grykes
(cracks) in between get larger. This process gives the pavement a block like
appearance.
Limestone Pavement
Clints (blocks)
Grykes (deep grooves)
Appearance Part 3
A process called solution takes place which is when acid rain dissolves the
limestone rock which makes up the limestone pavement. When this takes place
the carbonic acid runs over the top and down the sides of rocks called clints.
The acid then dissolves little grooves (runnels) in the clints (blocks of rocks),
which are called Karren. The clints also become rounder over time due to this
solution process so its hard angular edges are rounded off into smaller clints
called Rund Karren.
Limestone Pavement
Rund Karren (rounded blocks)
Karren (shallow grooves on clints)
Chemical Reaction Part 1
Solution, also called carbonation, is a type of chemical weathering affecting
limestone. It occurs because of the chemical make up of limestone and results
in the limestone being dissolved away.
Rain water mixes with carbon dioxide from natural (volcanoes) & human
(factories) sources, this forms carbonic acid; also known as acid rain. When it
falls on the limestone, (Calcium Carbonate chemical formula CaCO3) it dissolves
it to form calcite (called Calcium Hydrogen Carbonate).
You’ll need to be able to explain the chemical formula below.
H2 O
Water
+
CO2
Carbon
Dioxide
=
H2CO3
Carbonic
Acid
+
CaCO3
Calcium
Carbonate
=
H2CO3
Carbonic
Acid
Ca(HCO3)2
Calcium Hydrogen
Carbonate
Acid
Rain
Calcite
Chemical Reaction Part 2
The actual solution of the limestone, actually first takes place when it is
covered by soil, thousands of years ago. The carbonic acid develops as rain
water drains into the soil and combines with CO2, given off by rotting
vegetation. The soil is then often scraped off by a moving glacier exposing the
pavement to further solution as we have mentioned already.
Pre (Before) Ice Age
Soil (CO2 + H2O + Carbonic Acid)
Post (After) Ice Age
Limestone Blocks Exposed To acid
Rain After Soil Removed By Glaciers