Finger Rafting

Synonyms

Thrust structures

Definition

The formation of interlocking fingers when two “ice floes” alternately over- and under-ride one another during “rafting.”

Generation: Finger rafting is caused by two ice floes being forced together under the influence of atmospheric and oceanic stresses (Weeks and Anderson, 1958). It is understood that finger rafting is initiated by the presence of small overlapping regions. Such a region leads to vertical displacements of the two floes that are exactly out of phase with one another so that further forcing causes them to “cut” the fingers out of each other (Vella and Wettlaufer, 2007).

Occurrence: Finger rafting is generally observed in young, thin sea ice with thickness up to approximately 15 cm. The interaction of thicker ice floes leads to simple “rafting” for intermediate thicknesses or pressure ridging for thickness above around 1 m (Vella and Wettlaufer, 2008). Laboratory models using thin ($\approx 100\,\mu {\text{m}}$) floating wax...