Question

Difference between frost action and granular disintegration

Answer 1

Block disintegration
- It occurs in well-jointed rock such as granite.
- It is particularly effective in areas with great diurnal range of temperature (10ºC to 15ºC or more) and
barren rocks without a protective vegetation cover, e.g. in desertregions.
- Rocks are split along the joints into large rectangular-shaped blocks

Frost action
- It is most pronounced at high latitude or mountainous areas.
- Water thaws during daytime (above 0ºC) and seeps into the cracks of rock.
- When the temperature falls to below 0 ºC) water changes into ice (its volume increase 9%). The water
which has collected in the cracks or joints freezes and expands, so the cracks are enlarged.
- Repeated growth and melting of ice crystals in the cracks of rocks, set up forces and cause rocks to
loosen and break down into small, angular fragments.
- In mountainous areas, the broken rock material often rolls down the steep slopes. It comes to rest where
the slope becomes more gentle, to form what is known as scree(©¥®h°ï).
- Frost action is therefore composed of two actions - the wedging and the growth of inter pore ice
crystals. (e.g. When the pressure of the growth of the ice crystals exceeds the strength of the porous
materials, the rock will be broken down.)