We have carried out 2-D numerical simulations using the discrete element method (DEM) to investigate density-driven deformation in Martian volcanic edifices and how it affects the development of caldera complexes. These simulations demonstrate that the presence of a dense and weak cumulate body within a volcanic edifice strongly influences the volcano morphology and enhances volcanic spreading. The settling of a cumulate body generates distinctive structural and morphological features characteristic of Olympus Mons and Arsia Mons, including low flank slopes and pronounced summit calderas. We show that gravitational spreading of a cumulate body can play a primary role in the long-term development of calderas. We conclude that a cumulate body that is both shallow and wide could generate a single large depression similar to the Arsia-type caldera, while our simulations of a narrow cumulate body are capable of generating summit subsidence that is similar in dimension to the Olympus Mons caldera.