She first began defending the theory of continental drift in the 1950s and has been described as one 'of South Africa's foremost scientists in the field of Gondwana paleobotany and geology'.

Her dissertation for her master's degree was highly regarded by the Geological Society of South Africa leading to her being the first recipient of the Corstorphine Medal.

Although this was long before general acceptance of 'continental-drift', plate tectonics and sea-floor spreading, some saw the Antarctic fossil plants as compelling evidence for the existence of the former 'super-continent', Gondwana.

Therefore, she was influenced by Wegener’s hypothesis and became especially interested about the fact that early life on the earth was not evenly distributed, but that it was divided in zones.

The first one was: “If the position of the continents had not changed how could the same genera and even species of plants have migrated east, west and south across the wide oceans which now are separate them but have failed to reach North America, Europe and Asia along easy routes?” The second question was: “If the climatic zones were the same, how can we explain the fact that the fossil plants of peninsular India are closely comparable, and often identical with those of Australia, Africa south of the Sahara, Argentina and Brazil but above all, with those found in the heart of Antarctica at 86˚S where today no vascular plant could live?”[5] Plumstead also played a role in the development of the mobilism theory as she provided better information about Glossopteris that contributed to the interpretation and understanding of the division of Gondwana.

Plumstead made a great contribution to the understanding of Glossopteris, providing key evidence confirming the mobilist interpretation of Gondwana.