Geology and biological evolution of life are inseparable. More than half of the minerals now incorporated into the upper crust of our planet were produced by living organisms. The movement of continental plates has played a fundamental role in the recycling of mineral resources by the biosphere. Scientists now predict that tectonic activity may have been one of the prerequisites for the origin of life. The acceptance of continental drift by the scientific community and how it affected Earth’s history has furthered our understanding about our planet greatly.
Animations produced by Dr. Christopher Scotese (Northwestern University) are outstanding resource for understanding of continental dynamics going as far back as Ediacaran Period. Here, you can watch visualizations going as far back as the famous Cambrian Period during which life diversified into major biological kingdoms. The first two animations detail major continental movements traveling backwards and forwards through time. Other animations detail the geological events in three focal regions: the Indian subcontinent, Malayan archipelago and South America. The geological development of these regions have shed light into extraordinary levels of biological diversity in these areas.
Separation of the Indian Plate from the Gondwana beginning from 120 million years ago lead to a long-term isolation of the subcontinent. During this isolation the Indian plate moved from the southern hemisphere into the northern hemisphere with astonishing speed. During the late Cretaceous (80 – 65 mya), India was moving at rates of more than 15 cm/year. India’s northward race towards Asia may be something of a plate tectonic speed record. The reason it moved so quickly was because it was attached to a large oceanic slab of lithosphere that was subducting beneath the southern margin of Asia. As it crossed the tropical belt it experienced a wide range of climatic changes. It stayed as an isolated landmass for more than 70 million years until it collided with Asia. The collision initiated the formation of the Himalayas. The Western Ghats remained as a prominent feature during the geological migration. Long-term isolation enabled evolution of a very high proportion of endemic species. Later when it regained contact with adjacent continents the diversity increased with new migrants coming from Asia and Africa.
The next visualization focuses on Malay Archipelago. This region attracted attention of two of the pillars of biological evolution, Alfred Wallace and Charles Darwin. Wallace devoted the second half of his career to the region of shallow seas called “Wallacea” known to be one of the most biodiverse areas in the World. The region which includes the Coral Triangle, is a 6 million km2 area covering Indonesia, Malaysia, the Philippines, Papua New Guinea, Timor Leste and the Solomon Islands. The Coral Triangle harbors 76% of the world’s coral species, 6 of the world’s 7 marine turtle species, and more that 2,228 reef fish species. Darwin was also very interested in corals and even published a book in 1842 on bio-geological evolution of coral atolls.
The animation shows the plate tectonic history of India and Southeast Asia. The red dot shows location of Singapore. The animation begins with the modern world, but then fades back in time to 100 million years ago when India and Southeast Asia were separated by a wide ocean (Tethys Ocean). Animals living in India and Australia evolved in isolation giving rise to such oddities as the kangaroo and platypus. 50 million years ago India collided with Southeast Asia, allowing exchange of plants and animals. At around 10 million years ago Australia arrived at the southern border of Southeast Asia.
The geological history of South America is a curious one. The continent has formed a large chunk of Gondwana during the last 400 million years. Brazil is one of the few places on Earth that begins its journey in the tropics, moves south across the South Pole, then moves back to the tropics. The following visualization allows us to see events that lead to evolution of one of the most biologically diverse areas. The formation of the Andes mountain range has had a significant influence on evolution of life in South America especially the Amazons. It is also worth noting a series of marine incursions that invaded Amazon basin multiple times. Marine incursion hypothesis is still highly debated. During the Triassic, when Pangaea began to break up several rifts developed. During the Cretaceous Period, the Andes began to take their present form as a result of the uplifting, faulting and folding of sedimentary and metamorphic rocks of the ancient cratons to the east of the continent.
Rio was chosen as a visual reference. Chronologically, 100 million years ago, Rio nearly joined up with Angola across a closing South Atlantic. At 200 million years ago, Rio is located on a high plateau in the center of Pangea. At 300 million years ago, Rio is at the edge of the great Gondwanide ice cap. And finally, 400 million years ago, Rio is sitting atop the South Pole. What a surprising travel adventure for an iconic tropical city!
As much of the continental drift has happened in the southern hemisphere from the Cambrian until the Permian, a projection centering around the South Pole is very informative. The animation demonstrates how Antarctica has remained near the South Pole for more than 300 million years. During the Paleozoic, the South Pole moves from North Africa (500 Ma), across central Africa and eastern Brazil (400 Ma), and crosses into Antarctica by the end of the Paleozoic (250 Ma). As a visual reference the South Pole (small white dot) is kept fixed near the lower part of the screen. The colored regions are ocean floor that was created at mid-ocean ridges. The white areas are regions of ocean floor that have been subducted.