Why does plastic only occur below 50 meters of ice?

Why does plastic only occur below 50 meters of ice?

Why does plastic flow only occur below 50 meters of ice? It takes the weight of that much ice to cause the plastic flow.

What causes plastic flow to occur?

Plastic deformation is the permanent distortion that occurs when a material is subjected to tensile, compressive, bending, or torsion stresses that exceed its yield strength and cause it to elongate, compress, buckle, bend, or twist.

Why does plastic flow occur?

Plastic flow is a rheological phenomenon in which flowing behavior of the material occurs after the applied stress reaches a critical value (yield). This slope and the weight of the ice induce a shear stress throughout the mass. When subjected to a shear stress over time, ice will undergo creep, or plastic deformation.

Where does plastic flow occur in a glacier?

(b) Plastic flow: Occurs in the middle part of the glacier where the ice crystals deform plastically under the combined influence of the overlying ice and the downslope gravitational pull (Fig. 3).

How does plastic flow occur in a crystalline material?

Crystal-plastic flow occurs by two mechanisms: twinning and intracrystalline slip. Both these mechanisms accommodate deformation by shear of one section of a crystal with respect to another (Hancock, 1994).

How does plastic deformation occur in a glacier?

This process of plastic deformation (internal deformation) occurs because the ice crystals are able to slowly bend and change shape without breaking or cracking. Plastic deformation occurs below a depth of 50 meters (164 feet) from the surface of the glacier. [4]

Where does the ice flow in a glacier?

Glacial ice flows away from the zone of accumulation when the thick ice deforms plastically under its own weight. In a valley glacier the ice flows downslope from the zone of accumulation, while for a continental glacier the ice flows laterally outward and away from the zone of accumulation.

How are snowflakes used to form glacial ice?

A considerable amount of snow accumulation is necessary for glacial ice to form. It is imperative that more snow accumulates in the winter than that which melts away during the summer. Snowflakes are hexagonal crystals of frozen water; however, layers of fluffy snowflakes are not glacial ice…not yet at least.

How long does it take for glacial ice to form?

The firn and meltwater slowly recrystallize, forming glacial ice. This transformation process may take several decades to hundreds of years because the rate of glacial ice formation is highly dependent upon the amount of snowfall. (The recrystallization process means that glacial ice is really a type of metamorphic rock.)