Sixty-five million years ago, the continents were recognizable in outline but arranged in strikingly different positions, surrounded by shallow seas far more extensive than anything on Earth today. Pangaea had been breaking apart for over a hundred million years by that point, and most of the major landmasses we know had separated, but their locations and connections would look alien on a modern map. India was an island continent racing north through open ocean. Europe was a chain of islands. Australia still clung to Antarctica. And North America was split in two by an inland sea that was only just draining away.
A World in Transition
By 65 million years ago, the supercontinent Pangaea was ancient history. Its breakup had started around 200 million years ago, and by the Late Cretaceous, the major fragments had taken on shapes you could roughly match to today’s continents. But the arrangement was different enough that a time traveler would struggle to orient themselves. The Atlantic Ocean existed but was much narrower, especially in its northern reaches. The Tethys Sea, a vast tropical ocean, still stretched between Africa-Arabia and Eurasia. South America and Africa had been drifting apart for tens of millions of years, but the South Atlantic was a relatively young and narrow body of water compared to the broad expanse we see today. A comprehensive atlas of paleogeographic maps covering the last 750 million years illustrates how the continental arrangement at the K-Pg boundary was shaped by ongoing plate motions, fluctuating sea levels, opening ocean basins, and mountain-building episodes driven by plate collisions.1Annual Reviews. An Atlas of Phanerozoic Paleogeographic Maps: The Seas Come In and the Seas Go Out
Sea levels were dramatically higher than today. Estimates for global sea level near the end of the Cretaceous put it roughly 100 to 200 meters above present levels. This meant vast areas of continental crust that are now dry land were underwater, covered by warm, shallow seas. The result was a planet with less exposed land, more fragmented landmasses, and a very different pattern of animal and plant distribution than we see now.
North America Split by a Seaway
One of the most dramatic differences in the Late Cretaceous map was North America. For much of the Cretaceous, a shallow body of water called the Western Interior Seaway ran from the Gulf of Mexico to the Arctic Ocean, effectively cutting the continent into two large islands. The eastern half, called Appalachia, and the western half, called Laramidia, were home to distinct communities of dinosaurs and other animals that evolved in partial isolation from each other.
By 65 million years ago, this seaway was in its final stages, retreating as sediment filled its basin and sea levels began to drop. But it hadn’t vanished completely, and remnants of marine conditions persisted across parts of the central plains. The landscape of western North America was also being reshaped by the Laramide orogeny, the mountain-building event that created the Rocky Mountains. The prevailing model holds that flat subduction of the Farallon oceanic plate beneath the continent generated enormous compressive forces deep inland, pushing up the basement rocks that form the Rockies.2PubMed. Formation of the rocky mountains, Western United States: a continuum computer model The resulting east-west to northeast-southwest compression created the characteristic thrust and reverse faults seen across the region today.
This was not a quick event. Research on how the strength of the North American lithosphere changed over time shows that the transition from the earlier “Sevier” style of mountain-building (a volcanic arc along the coast, like the modern Andes) to the deeper “Laramide” style (thick-skinned faulting far from the plate edge) happened gradually during the Late Cretaceous.3Journal of Geophysical Research: Solid Earth. Laramide Orogenesis Driven by Late Cretaceous Weakening of the North American Lithosphere At the time the asteroid hit, the Rockies were actively rising but nowhere near their modern height, and the western interior was a patchwork of broad basins, newly uplifted ranges, and remnant marine environments.
Volcanic activity also accompanied the orogeny. Analysis of Late Cretaceous volcanic rocks in the Southern Rockies region of Colorado shows that melting of the mantle above the shallowly subducting Farallon plate produced magma that interacted with older continental rock on its way to the surface.4Geosphere. Mantle melting in regions of thick continental lithosphere: Examples from Late Cretaceous and younger volcanic rocks, Southern Rocky Mountains, Colorado (USA) So western North America at 65 million years ago was geologically active, volcanically productive, and still partly underwater.
India Racing North Through Open Ocean
India’s story at 65 million years ago is one of the most remarkable in all of plate tectonics. Having broken away from the eastern coast of Africa as part of the larger Gondwana supercontinent, then separating from Madagascar, India was an isolated landmass sprinting northward through the Tethys Ocean toward its eventual collision with Asia. Around 67 million years ago, the Indian plate accelerated to roughly 20 centimeters per year, channeled between two great transform faults on its western and eastern flanks.5Proceedings of the Indian National Science Academy. India’s Northward Drift from Gondwana to Asia During the Late Cretaceous-Eocene That rate is extraordinary. Most tectonic plates move a few centimeters per year. India was moving at roughly four times that speed, making it one of the fastest-moving plates in Earth’s recorded history.6Geological Society of America Special Papers. The Restless Indian Plate and Its Epic Voyage from Gondwana to Asia: Its Tectonic, Paleoclimatic, and Paleobiogeographic Evolution
Paleomagnetic data suggests that even within the Indian plate, different pieces were moving at different rates. The Tethyan Himalaya terrane, the leading edge of India, appears to have been moving north at an even faster clip than the main plate, roughly 260 millimeters per year between about 75 and 61 million years ago. This suggests the leading edge may have rifted away from the Indian mainland before colliding with Asia.7PubMed Central. Rapid drift of the Tethyan Himalaya terrane before two-stage India-Asia collision The collision itself likely began in stages between 65 and 55 million years ago, and the final suturing happened millions of years later.8Journal of Biogeography. The biogeographic and tectonic history of India
At the same time India was crossing the ocean, a massive volcanic event was underway on its surface. The Deccan Traps, one of the largest volcanic provinces on Earth, were erupting around this very time. Radiometric dating places the main pulse of Deccan volcanism at about 65.5 million years ago, coinciding almost exactly with the end-Cretaceous mass extinction.9Reviews of Geophysics. Paleomagnetism and age determinations of the Deccan Traps (India): Results of a Nagpur‐Bombay Traverse and review of earlier work The lava flows covered an area of about 500,000 square kilometers in what is now central-western India, and the original extent before erosion and rifting may have been closer to 1.5 million square kilometers.10Journal of Volcanology and Geothermal Research. Correlation of the Deccan and Rajahmundry Trap lavas: Are these the longest and largest lava flows on Earth? So the picture of India at 65 million years ago is a fast-moving island subcontinent, somewhere in the southern tropics, blanketed in volcanic eruptions on a scale difficult to imagine.
Europe as an Archipelago
Europe barely existed as a coherent landmass at 65 million years ago. Much of what is now the European continent was flooded by shallow seas, and the remaining dry land formed an island archipelago scattered across the northern edge of the Tethys Ocean. Some of these islands were quite small. The fauna living on these islands showed the classic signatures of island life: low species diversity, a bias toward more ancient lineages, and body size changes including dwarfism.11PubMed Central. Island life in the Cretaceous – faunal composition, biogeography, evolution, and extinction of land-living vertebrates on the Late Cretaceous European archipelago The dinosaurs of Late Cretaceous Europe tended to be smaller than their relatives elsewhere, likely because island ecosystems cannot support the same body sizes as large continents.
To the south, the Tethys Ocean separated this European archipelago from the slowly approaching African plate. The Mediterranean Sea did not yet exist in its modern form. Instead, the Tethys was a wide tropical ocean whose closure over the next tens of millions of years would eventually create the Mediterranean basin and build the Alps, Carpathians, and other mountain ranges of southern Europe. At 65 million years ago, that closure was still in its early stages.
South America, Antarctica, and Australia
The southern continents were in various stages of separating from one another. South America had been drifting away from Africa for roughly 30 million years by the end of the Cretaceous, but the South Atlantic between them was still narrow. Meanwhile, South America remained physically connected to Antarctica through what is now the Antarctic Peninsula region. Fossil data confirms that terrestrial animals were actively migrating between these landmasses during the Cretaceous.12Palaeogeography, Palaeoclimatology, Palaeoecology. Cretaceous paleogeography of Antarctica The Drake Passage, the body of water that now separates South America from Antarctica and allows the Antarctic Circumpolar Current to flow, would not open for another 30 million years or so. Its eventual opening transformed global ocean circulation and helped plunge Antarctica into its deep freeze.
Australia was also still connected to Antarctica at 65 million years ago, though the connection was beginning to fail. Rifting between eastern Australia and Antarctica was underway, with the continental crust stretching and thinning in a process that would eventually create the Southern Ocean. Around 65 million years ago, in the eastern part of the Australo-Antarctic continent, the rift axis was shifting and a left-lateral shear zone was forming between Tasmania and the conjugate Antarctic continental margin.13Journal of Mining Institute. Early stages of ocean formation between Australia and Antarctica Full separation was still millions of years away, meaning that at the time of the mass extinction, a land animal could theoretically walk from Antarctica to Australia. Antarctica itself was not the frozen wasteland it is today. With higher global temperatures and no circumpolar current, it supported forests and a range of terrestrial life.
Off the eastern margin of Australia, the largely submerged continent of Zealandia had already undergone the crustal thinning that defines it today. Zealandia is about 94 percent underwater now, and that submergence is mainly the result of widespread Late Cretaceous crustal thinning that preceded the breakup of the Gondwana supercontinent.14GSA Today. Zealandia: Earth’s Hidden Continent At 65 million years ago, Zealandia was already mostly beneath the waves, though parts of it, including what is now New Zealand, remained above sea level.
Africa and Madagascar
Africa at 65 million years ago was more isolated than you might expect. It had separated from South America, and India-Madagascar had already rifted away from its eastern coast long before. By about 83 million years ago, all the major Gondwanan fragments that bordered Africa were separated by tracts of water.15PubMed. Reconciling the origins of Africa, India and Madagascar with vertebrate dispersal scenarios Africa was drifting northward but had not yet collided with Eurasia. The Tethys Ocean still lay between them, and Africa essentially functioned as a large island continent with its own distinctive fauna. The Seychelles microcontinent, which had been part of the India-Madagascar block, separated from India right around 65 million years ago as India continued its northward dash.8Journal of Biogeography. The biogeographic and tectonic history of India
Madagascar itself had been an island for at least 20 million years by this point, having separated from India sometime between 84 and 96 million years ago. Its long isolation explains why its plants and animals evolved along such unique paths, a pattern that began in the Cretaceous and continued through the Cenozoic.
The Tethys Ocean and Global Circulation
One of the most important features of the 65-million-year-old Earth was the Tethys Ocean, a vast tropical seaway that wrapped around much of the equatorial zone. With the Atlantic still narrow and the connection between North and South America not yet established (the Isthmus of Panama wouldn’t close for another 60 million years), ocean currents could flow in patterns completely unlike those of the modern world. Numerical simulations of Late Cretaceous ocean circulation show that a circumglobal tropical current flowed westward through the Tethys, threading between the continental fragments.16PubMed. Numerical Simulation of the Cretaceous Tethys Circumglobal Current This current redistributed heat across the tropics and influenced climate patterns globally.
The eventual closure of the Tethys tens of millions of years later, as Africa and India collided with Eurasia, shut down this equatorial circulation and fundamentally reorganized ocean currents worldwide. That closure isolated the Atlantic-Mediterranean system from the Indo-Pacific and reshaped aquatic biodiversity across the planet.17PubMed. Tethyan changes shaped aquatic diversification At 65 million years ago, though, the Tethys was still wide open, and the global ocean was warmer and less stratified than it is today.
The climate itself was considerably warmer. There were no permanent ice sheets at either pole. Global temperatures were high enough that forests grew near the Arctic and Antarctic circles. Sea levels reflected this warmth: peak warm periods during the Paleocene and early Eocene (the interval just after 65 million years ago) saw elevated global sea levels, high atmospheric CO₂, and effectively ice-free conditions.18Earth Science, Systems and Society. Global Mean and Relative Sea-Level Changes Over the Past 66 Myr: Implications for Early Eocene Ice Sheets The world at the K-Pg boundary was a greenhouse planet, and the high sea levels that came with it shaped every continent’s coastline.
Where the Asteroid Hit
The Chicxulub impact that ended the Cretaceous struck what is now the Yucatán Peninsula of Mexico, but the geography of the impact site was very different from what you see there today. At 65 million years ago, the Yucatán was not a peninsula jutting into the Gulf of Mexico. It was the edge of a carbonate platform along a shallow tropical sea. The impact site itself was a carbonate ramp with water depths averaging around 600 meters, shallowing to roughly 100 meters in the south-southwest and deepening to about 2 kilometers to the north-northeast.19Scientific Reports. Life before impact in the Chicxulub area: unique marine ichnological signatures preserved in crater suevite The asteroid did not hit dry land. It slammed into a relatively shallow sea floor made of limestone and evaporite rocks, and this geology mattered enormously for the aftermath. The vaporized carbonate and sulfate rocks injected massive amounts of carbon dioxide and sulfur aerosols into the atmosphere, amplifying the climatic catastrophe.
The Gulf of Mexico itself was a partially enclosed basin at the time, and the impact generated tsunamis that left deposits traceable across the Caribbean and along what was then the southeastern coast of North America. The Western Interior Seaway, still draining away to the north, may have channeled some of these effects deep into the continental interior.
Land Bridges and Animal Migration
The question of which continents were connected to which others at 65 million years ago matters enormously for understanding the distribution of life. In the Northern Hemisphere, land bridges occasionally connected North America to Europe and Asia, though these connections were intermittent and depended on sea level. The De Geer route, a land bridge across the northern Atlantic between Greenland and Scandinavia, appears to have been available during the latest Cretaceous and into the early Paleocene.20Journal of Biogeography. The De Geer, Thulean and Beringia routes: key concepts for understanding early Cenozoic biogeography Beringia, the land bridge between northeastern Asia and northwestern North America, also existed at various times. These connections allowed dinosaurs and later mammals to disperse between continents, explaining why closely related species show up in the fossil record of both North America and Asia during this period.
In the southern hemisphere, as noted earlier, South America and Antarctica were still connected, and Antarctica and Australia were still joined. This created a chain of southern landmasses that animals could traverse, and fossil evidence supports active migration along this route during the Cretaceous.12Palaeogeography, Palaeoclimatology, Palaeoecology. Cretaceous paleogeography of Antarctica The progressive isolation of these southern continents over the following tens of millions of years profoundly shaped the evolution of their faunas. Australia’s unique marsupial radiation, for instance, is a direct consequence of that continent’s eventual separation from Antarctica and its long subsequent isolation.
How Scientists Build These Maps
Reconstructing the position of continents 65 million years ago is not guesswork. It draws on multiple independent lines of evidence. Paleomagnetism is the most powerful tool: when volcanic rocks cool or sediments settle, magnetic minerals align with Earth’s magnetic field at the time, recording both the direction to the magnetic pole and the latitude where the rock formed. By measuring these magnetic signatures in rocks of known age, geologists can work out where a given piece of crust was sitting at the time the rock formed.21Geological Magazine. The integration of palaeomagnetism, the geological record and mantle tomography in the location of ancient continents
Ocean floor magnetic anomalies add another layer of precision. As new ocean crust forms at mid-ocean ridges and spreads outward, it records reversals in Earth’s magnetic field as symmetrical stripes on either side of the ridge. By matching these stripe patterns and dating them, scientists can calculate exactly how fast and in what direction ocean basins have opened. For the period since the Jurassic, about 200 million years ago, this magnetic record gives high-resolution constraints on the relative positions of the plates.
Fossils provide a biological cross-check. When closely related species appear on two continents that are now separated by an ocean, it suggests either a past physical connection or a plausible dispersal route. The distribution of Cretaceous dinosaurs, freshwater fish, and plants has been instrumental in testing and refining plate reconstructions. More recently, mantle tomography, which images the deep interior of the Earth using seismic waves, has revealed remnants of ancient subducted ocean plates sinking through the mantle. These slabs act as a kind of geological memory, recording the locations of past subduction zones and helping scientists constrain which oceans existed where. The integration of all these methods produces reconstructions that, while never perfect, are robust enough to paint a detailed picture of where the continents sat at any given time in the last few hundred million years.
Deccan Volcanism and the Twin Catastrophe
The coincidence of the Deccan Traps eruption with the K-Pg mass extinction has fueled decades of scientific debate. The lava province is enormous. Even after 65 million years of erosion, the remaining Deccan basalts cover about 500,000 square kilometers, and the original extent may have been three times that.10Journal of Volcanology and Geothermal Research. Correlation of the Deccan and Rajahmundry Trap lavas: Are these the longest and largest lava flows on Earth? The eruptions released massive quantities of sulfur dioxide and carbon dioxide, which would have caused short-term cooling (from sulfate aerosols reflecting sunlight) and long-term warming (from greenhouse gases). Whether the Deccan eruptions contributed meaningfully to the extinction, or whether the Chicxulub impact alone was sufficient, remains one of the more contentious questions in Earth science. What is beyond dispute is the geographic fact: at the moment of the extinction, India was positioned in the southern tropics, adrift between Africa and Asia, and covered in one of the largest volcanic eruptions in Earth’s history. The tectonic and volcanic geography of the planet at 65 million years ago was not just a backdrop to the mass extinction. It was part of the story.