The periglacial environment
155
Figure 7.8. Planar clasts with vertical disposition due to frost-heaving action. Sierra de Javalambre in the
Iberian Range, Teruel Province, Spain.
Other frost heaving mechanisms relate to ice needles or pipkrake. These are elongated
ice crystals with sizes ranging from a few millimetres to 40 cm that form perpendicular
and close to the surface. They are particularly common in alpine environments. These
crystals lift clasts as they grow and subsequently collapse during thaw. This process causes
a sorting of the soil particles. The nubbins are elongated or oval-shaped bulges surface
3
~4
r
9 56
"7
Top row = During freezing
Botttom row = During thawing
Figure 7.9. Lifting of clasts by frost action (Beskow, 1930; in Washburn, 1979, Figure 4.3)
FT -- Freezing front, Striped pattern -- ice lenses.
155
Figure 7.8. Planar clasts with vertical disposition due to frost-heaving action. Sierra de Javalambre in the
Iberian Range, Teruel Province, Spain.
Other frost heaving mechanisms relate to ice needles or pipkrake. These are elongated
ice crystals with sizes ranging from a few millimetres to 40 cm that form perpendicular
and close to the surface. They are particularly common in alpine environments. These
crystals lift clasts as they grow and subsequently collapse during thaw. This process causes
a sorting of the soil particles. The nubbins are elongated or oval-shaped bulges surface
3
~4
r
9 56
"7
Top row = During freezing
Botttom row = During thawing
Figure 7.9. Lifting of clasts by frost action (Beskow, 1930; in Washburn, 1979, Figure 4.3)
FT -- Freezing front, Striped pattern -- ice lenses.