The climatic shift that was a major contributing factor to the collapse of the viking colonies is known as the

Greenland Norse collapse

Explanation:

The southern Greenland Vikings numbering 5000 at their peak never gave up their old way of lifestyle and did not adopt that of the Northern Inuits who arrived a century later after them. The study suspects that the climate factors became dominant and they were destroyed by the shifting nature of mother earth hence they starved to death and could not adapt to the present change in weather patterns this society collapsed. Some theories say soil grazing and over-exploitation of land lead to the effect of black deaths and the creation of ice age. It indicated that the number of fertile women dropped and thus population could not sustain itself.

Mantle convection is the process that drives plate tectonics. the theory of plate tectonics states that the crust is divided into plates that float on the semi molten mantle below. the circular motion of the magma as it slowly rises and falls or move though convection cells drags the plates along causing them to move. the heat source in the lamp would represent the earth's core. the core is the source of energy that drives convection in the mantle. the lava represents molten magma under the earth's surface. if the lava lamp had floating pieces they would move as the circular motion of the lava in the lamp as it rises and falls would move them along the surface. these floating pieces would represent pieces of the earth's crust. 

Brand c i think that should be it