The arrangement and movement of continents is one of the most powerful forces shaping both Earth’s climate and the diversity of life on the planet. Over hundreds of millions of years, tectonic plates have split apart, collided, and drifted across latitudes, and each shift has reshaped ocean currents, altered atmospheric chemistry, raised mountain barriers, and opened or closed corridors for species migration. The interplay between geology, climate, and biodiversity is not a simple chain of cause and effect but a web of feedbacks, where breaking a supercontinent apart can simultaneously cool the planet, create new shallow seas, and generate the geographic isolation that drives species to diverge.
How Breaking Continents Apart Fuels Marine Diversity
One of the clearest geological signals in the fossil record is the link between continental fragmentation and the richness of marine life. When a supercontinent like Pangaea begins to rift apart, new coastlines form, shallow seas flood the widening gaps between landmasses, and ocean basins multiply. Each of these changes creates habitat. A quantitative analysis of the entire Phanerozoic (roughly the last 540 million years) found a strong positive correlation between the degree of continental fragmentation and the number of marine invertebrate genera alive at any given time. The relationship holds even after accounting for uneven sampling and the varying amount of marine rock available to paleontologists. Fragmentation during the Mesozoic breakup of Pangaea appears to have exerted what the authors call a “first-order control” on the long-term rise of marine animal diversity.
1PubMed Central. Plate tectonic regulation of global marine animal diversityThere is an asymmetry worth noting: fragmentation actively promotes increasing richness, but when continents reassemble, the negative effect on diversity is comparatively small and more of a stabilizing force than a catastrophic one. In other words, stitching landmasses together does not simply reverse the gains made during breakup. The diversity built up during fragmentation phases tends to persist, at least partially, into subsequent coalescence phases.
Earth’s Geological Thermostat
Continents do not just passively sit in the path of ocean currents. They actively regulate Earth’s temperature over millions of years through a process called silicate weathering. When rain falls on exposed rock, it reacts with silicate minerals and pulls carbon dioxide out of the atmosphere. The dissolved carbon eventually reaches the ocean, where it is locked into carbonate sediments on the seafloor. This acts as a slow thermostat: more CO₂ warms the planet, which speeds up weathering, which draws down CO₂ and cools things back. Roughly half of this global CO₂ drawdown happens in active mountain belts, where fresh rock is constantly being pushed upward and exposed to the elements.
2PubMed Central. A framework for predicting global silicate weathering and CO2 drawdown rates over geologic time-scalesThe speed of this thermostat matters. Modeling work has estimated the characteristic timescale for silicate weathering to substantially draw down a CO₂ perturbation at roughly 240,000 years, with a range between about 170,000 and 380,000 years.
3Global Biogeochemical Cycles. The time scale of the silicate weathering negative feedback on atmospheric CO2That is fast enough to matter over geological epochs but far too slow to counteract human emissions on a human timescale. The position and height of mountain ranges therefore exerts a quiet, persistent influence on how much CO₂ the atmosphere holds at any given geological moment, and by extension, on global temperature and the climate niches available to living things.
4Global Biogeochemical Cycles. Evolution of the Global Carbon Cycle and Climate Regulation on EarthOcean Gateways and Dramatic Climate Shifts
Some of the most abrupt climate transitions in Earth’s history trace back to the opening or closing of narrow oceanic passages between continental blocks. The Eocene-Oligocene transition, around 34 million years ago, saw the planet lurch from a warm greenhouse state toward the glaciation of Antarctica. Modeling and proxy evidence point to changes in Atlantic-Arctic gateways as a critical factor. When the connection between the Arctic and North Atlantic was shallow, it restricted the southward flow of fresh surface water, allowing deep-water formation in the North Atlantic. That circulation pattern cooled the Southern Hemisphere by several degrees, setting the stage for Antarctic ice sheets. When the gateway later deepened, the overturning weakened, shifting cooling to the Northern Hemisphere and promoting glaciation there too.
5PubMed Central. Climate transition at the Eocene-Oligocene influenced by bathymetric changes to the Atlantic-Arctic oceanic gatewaysIn the Southern Ocean, a similar story played out as the Drake Passage and the Tasmanian Gateway widened. Before those passages opened, large wind-driven gyres in the subpolar Pacific and Atlantic carried warm equatorial surface water toward Antarctica, keeping coastal sea surface temperatures as high as 15 to 19°C. As gateways deepened, those gyres weakened, and surface waters along the entire Antarctic coast cooled by 2 to 3.5°C. The key change was not the sudden onset of a strong circumpolar current, as textbooks sometimes suggest, but rather the weakening of the warm-water gyres that had been hugging the coast.
6Nature Communications. Gateway-driven weakening of ocean gyres leads to Southern Ocean coolingMountain Building as a Biodiversity Engine
Mountains are some of the most species-rich places on Earth, and their formation by tectonic uplift is a direct driver of that richness. Rising terrain creates new elevational zones, fragments populations with ridges and valleys, and generates steep environmental gradients over short distances. All of these conditions favor the evolution of new species. A review of the mechanisms at work concluded that high mountain biodiversity reflects the interplay of faster speciation rates, opportunities for lineages to coexist at different elevations, and the persistence of populations in topographically sheltered spots during climate swings.
7PubMed. Building mountain biodiversity: Geological and evolutionary processesThe Hengduan Mountains in southwestern China offer a concrete example. Phylogenetic analyses of the region’s flora show that roughly 8 million years ago, the rate of in situ diversification jumped sharply, significantly exceeding the rates observed in the geologically older Tibetan Plateau and Himalayas. That timing lines up with independent geological estimates of when the Hengduan range was being most actively uplifted.
8PubMed Central. Uplift-driven diversification in the Hengduan Mountains, a temperate biodiversity hotspotMore recently, coupled landscape-biological simulations focusing on small mammals showed that biodiversity increases with both the magnitude and the rate of tectonic uplift, and that the signal is visible not just on mountaintops but in downstream depositional lowlands, recorded in the fossil record over millions of years.
9PubMed. Direct effects of mountain uplift and topography on biodiversityRain Shadows, Monsoons, and the Climate Consequences of Uplift
Mountains do not just create new habitats vertically. They reshape rainfall patterns across entire regions. As a mountain range rises, it forces moist air upward on the windward side, wringing out precipitation. The leeward side dries out, sometimes dramatically. In Patagonia, paleosol evidence shows that the uplift of the North Patagonian Andes triggered a shift from wetter to drier conditions, though the rain shadow was not fully established until about 14.6 million years ago even though the tectonic process started around 19 million years ago.
10GSA Bulletin. Multiproxy paleosol evidence for a rain shadow effect linked to Miocene uplift of the North Patagonian AndesThe Hengduan Mountains illustrate a more intricate feedback. Climate modeling shows that the deep valleys carved by erosion into the mountain range actually increase precipitation in some areas by about 20%, setting up a positive feedback loop: more rain drives more erosion, which deepens valleys, which channels more moisture. The authors suggest this feedback between topographic roughness and precipitation may have influenced the diversification of local organisms.
11Journal of Geophysical Research: Atmospheres. Assessing the Regional Climate Response to Different Hengduan Mountains Geometries With a High‐Resolution Regional Climate ModelAt a continental scale, the phased uplift of the Tibetan Plateau reshaped the Asian monsoon system. Simulations show that as the plateau rose, its elevated surface acted as a heat source that strengthened the monsoon, pulling more moisture inland during summer. This amplified the sensitivity of East Asian monsoon precipitation to orbital forcing, so that summer rainfall in southern regions increased while northern regions dried out.
12Journal of Geophysical Research: Atmospheres. Tibetan Plateau Uplift Changed the Asian Climate and Regulated Its Responses to Orbital Forcing During the Late Eocene to Early MioceneNumerical climate experiments using stepwise increases in mountain-plateau elevation support a direct link between the stages of Himalayan-Tibetan uplift and the evolution of the monsoon, including its connection to Northern Hemisphere glaciation.
13Nature. Evolution of Asian monsoons and phased uplift of the Himalaya–Tibetan plateau since Late Miocene timesLand Bridges and the Great American Biotic Interchange
When tectonic forces push continents close enough for a land bridge to form, the biological consequences can be spectacular. The closure of the Central American Seaway and the rise of the Panamanian land bridge connected North and South America, ending millions of years of South American faunal isolation. The classic view held that mammal exchange began in pulses around 2.8 million years ago, but new low-latitude fossil data from Mexico reveal a longer, three-phase process. Starting around 10 million years ago, northern mammals began accumulating in a Mexican “holding pen.” Between 7 and 3 million years ago, dispersal accelerated along a strong north-south gradient. The well-known taxonomic pulses from around 2.8 million years ago represent only the final phase.
14PubMed. A 10-million-year biogeographic holding pen primed the Great American Biotic InterchangeThe interchange was not just about mammals walking across a bridge. It triggered competition between previously isolated faunas, drove some lineages to extinction, and sparked new waves of adaptation and speciation. Bird diversification across Mesoamerica, for instance, including elevational zonation of species into distinct altitude bands, traces back to events set in motion by the land bridge’s formation.
15PubMed Central. An elevational shift facilitated the Mesoamerican diversification of Azure-hooded Jays (Cyanolyca cucullata) during the Great American Biotic InterchangeContinental Drift and the Legacy of Pangaea in Modern Species
The breakup of Pangaea did not just reshuffle coastlines. It physically carried populations apart on drifting landmasses, and many modern lineages still bear the imprint. Amphibians are a striking case: a large-scale biogeographic analysis of over 3,300 species found that the Pangaean origin and subsequent fragmentation into Laurasia and Gondwana explain a large proportion of where extant species live today, roughly 300 million years later. Most amphibian species show high specificity for particular habitats and climatic niches, making long-distance ocean crossings unlikely and leaving them as living records of ancient continental positions.
16Systematic Biology. Biogeographic Analysis Reveals Ancient Continental Vicariance and Recent Oceanic Dispersal in AmphibiansSouthern Hemisphere freshwater crayfish tell a similar story. Phylogenetic and fossil evidence shows that their divergence follows an east-west pattern consistent with Gondwanan breakup. The split between Australian and New Zealand lineages, estimated at 109 to 160 million years ago, actually predates the physical rifting at around 80 million years ago, suggesting these lineages were already established before the continents fully separated.
17Journal of Biogeography. Gondwanan radiation of the Southern Hemisphere crayfishes (Decapoda: Parastacidae): evidence from fossils and moleculesIsland Fragments and Endemic Evolution
When a continental fragment drifts into isolation, evolution takes a distinctive turn. Madagascar separated from the Indian subcontinent roughly 88 million years ago and has been isolated ever since. The result is a biota that is both hyperdiverse and exceptionally endemic: a huge fraction of its species are found nowhere else on Earth.
18PubMed. Madagascar’s extraordinary biodiversity: Evolution, distribution, and useAncient fragment islands like Madagascar and New Zealand accumulate “paleo-endemics” through a process of relictualization. Given enough time in isolation, lineages diverge to the point where entire genera are unique to the island, a level of distinctiveness that is rare on mainland continents.
19PubMed. Arthropods on islands: colonization, speciation, and conservationVolcanic Catastrophes Tied to Continental Geology
Not all tectonic influences on biodiversity are gradual. Large igneous provinces, massive outpourings of lava linked to mantle plumes and continental rifting, have coincided with several of Earth’s worst mass extinctions. The total volume of lava turns out to be less important than the speed and character of gas release. The most lethal episodes share a pattern: the main extinction pulse hits at the onset of volcanism, often during explosive eruptions that inject enormous quantities of CO₂ and sulfur dioxide into the atmosphere in a single geological instant. Warming and widespread ocean oxygen depletion feature repeatedly in the kill mechanisms, making a province’s ability to trigger these conditions the single most important factor governing how deadly it is.
20Special Paper – Geological Society of America. Large igneous provinces and mass extinctions: An updateGlacial Refugia and Genetic Diversity
The ice ages of the last 2.6 million years repeatedly forced species out of high-latitude habitats and into warmer refugia, usually at lower latitudes. Where those refugia were located, and how large they were, shaped the genetic diversity we see in modern populations. Fossil records and phylogeographic studies converge on this picture, showing that species retreated to sheltered areas during glacial maxima and re-expanded when ice receded.
21PubMed. Phylogeographic insights into cryptic glacial refugiaIn western North America, modeling of glacial refugia for 22 tree species revealed a tight relationship between the size of a species’ glacial refuge and its modern genetic diversity. Species with large, widespread refugia developed strong genetic differentiation into subspecies, while species squeezed into small refugia show little differentiation and low genetic diversity today, even when they now occupy vast geographic ranges. The correlation between the size of modeled refugia and the richness of rare genetic variants was remarkably strong.
22PubMed Central. Glacial refugia and modern genetic diversity of 22 western North American tree speciesIn northwestern North America, the story is even more complex. Two major refugia, Beringia and the Pacific Northwest, were connected by mountain chains and bordered by the Pacific, offering diverse microrefugia. Researchers found “refugia within refugia” in both areas, as well as evidence for cryptic refugia in the Alexander Archipelago, Haida Gwaii, and even within the ice sheets themselves.
23Molecular Ecology. Of glaciers and refugia: a decade of study sheds new light on the phylogeography of northwestern North AmericaRivers, Rifts, and Freshwater Species
Continental dynamics shape freshwater biodiversity through a mechanism that is easy to overlook: the rearrangement of river drainages. Tectonic uplift, faulting, and erosion can abruptly reroute a river so that it captures part of a neighboring drainage basin. When that happens, aquatic organisms suddenly gain access to a new basin or find themselves isolated from former neighbors. Modeling work shows that when river captures are frequent, speciation rates climb faster than extinction rates, producing a net increase in freshwater biodiversity.
24Journal of Geophysical Research: Earth Surface. Modeling the Evolution of Aquatic Organisms in Dynamic River BasinsContinental rifting can produce even more dramatic results. The East African Rift created Lake Malawi, where tectonically driven changes in the lake’s outlet elevation and water level generated cycles of environmental fluctuation over the past 1.2 million years. Repeated crossings of environmental thresholds drove a rhythm of diversification, hybridization, and extinction that closely matches the phylogenetic history of the lake’s famous cichlid fish radiation.
25PubMed Central. Environmental change explains cichlid adaptive radiation at Lake Malawi over the past 1.2 million yearsBedrock, Dust, and Biological Productivity
The type of rock that a continent exposes at its surface matters for life in ways that go beyond weathering and CO₂. In the Sierra Nevada, tree canopy cover, a proxy for forest productivity, varies by more than an order of magnitude depending on the underlying bedrock, changing abruptly at mapped boundaries between different rock types. The variation correlates with bedrock concentrations of plant-essential nutrients like phosphorus, pointing to a bottom-up geological control on where forests thrive and where they struggle.
26PubMed Central. Bedrock composition regulates mountain ecosystems and landscape evolutionContinental geology also feeds the ocean. Wind carries mineral dust from arid continental interiors out over the sea, delivering iron and other micronutrients to surface waters where phytoplankton need them. In the Southern Ocean, an estimated one-third of biological productivity is supported by dust-borne iron. The size and aridity of continents, both products of tectonic positioning and climate, therefore influence marine food webs thousands of kilometers from shore, and the effect scales up on glacial-interglacial timescales as dust fluxes rise and fall with continental aridity and ice-sheet extent.
27PubMed. One-third of Southern Ocean productivity is supported by dust depositionWhat the Next Supercontinent Could Mean for Climate
Plate tectonics has not stopped. Current projections of plate motion suggest that a new supercontinent will form 200 to 250 million years from now, though its latitude remains uncertain. Climate simulations of two scenarios, one with the supercontinent at low latitudes and another at high northern latitudes with a separate Antarctic landmass, produce strikingly different outcomes. Global mean surface temperatures differ by several degrees between the two, driven mainly by the topographic height of high-latitude continental masses: taller terrain promotes snowfall, raises planetary albedo, and cools the planet further.
28Geochemistry, Geophysics, Geosystems. The Climates of Earth’s Next Supercontinent: Effects of Tectonics, Rotation Rate, and InsolationWhether that future supercontinent sits on the equator or wraps around a pole will determine whether Earth’s next geological chapter is warm or cold, whether shallow seas proliferate or shrink, and whether continental margins offer the kind of fragmented, habitat-rich coastlines that have historically driven surges in biodiversity. The deep past makes clear that the answers to these questions have never been fixed. They have always been moving, at the speed of tectonic plates.