What Will the Earth Look Like in 100 Million Years?

Earth 100 million years from now will be a planet mid-stride in the assembly of its next supercontinent, with the Atlantic Ocean narrowing or the Pacific shrinking (or both), a Sun roughly one percent brighter than today, longer days, unfamiliar coastlines, and ecosystems that would be barely recognizable. The broad strokes are surprisingly well constrained by physics and geology, even if the fine details remain speculative. What makes the question compelling is that scientists can already sketch several competing visions of this future world, each grounded in the same plate-tectonic and stellar-evolution models that successfully explain Earth’s past.

The Continents Are on the Move

The most dramatic change 100 million years from now will be geographic. Earth’s continents are drifting at rates of a few centimeters per year, roughly the speed your fingernails grow. Over 100 million years those centimeters add up to thousands of kilometers. The result: a global map that would look alien to anyone alive today.

The scientific consensus is that Earth’s landmasses are heading toward another supercontinent, but researchers disagree on which ocean will close first. Three leading scenarios have names. In the “Pangea Ultima” model, the Atlantic Ocean reverses course and closes over roughly 150 million years, reassembling a Pangea-like landmass in approximately the same position as the original.¹ In the competing “Amasia” model, the Pacific Ocean closes instead, drawing the Americas toward Asia. A 2022 modeling study argued that the Pacific closure (extroversion) is the more likely path because Earth’s oceanic crust has been thinning over billions of years, making older Pacific-floor lithosphere weaker and easier to subduct.² A third scenario, called “Aurica,” proposes that both the Pacific and Atlantic close simultaneously, producing a supercontinent centered on present-day Southeast Asia.³

At the 100-million-year mark, none of these supercontinents will have fully assembled; that finale is generally expected around 200 to 250 million years from now. But 100 million years is enough time for the map to look strikingly different. The Atlantic could be considerably narrower, or large chunks of the Pacific rim could have collided, depending on which scenario plays out. Australia will almost certainly have drifted north and collided with or come very close to Southeast Asia. Africa will have continued pushing into Europe, closing the Mediterranean entirely.

New Mountain Ranges, Vanishing Seas

Continental collisions build mountains. The Himalayas exist because India crashed into Asia roughly 50 million years ago, and that collision is still ongoing. In 100 million years, new collision zones will produce mountain ranges that dwarf anything we have today. The Africa–Europe convergence is already in its early stages. Geophysical data show that the western Mediterranean is undergoing progressive inversion and closure, with a new convergent boundary developing along North Africa’s coast.⁴ Given 100 million more years, the Mediterranean Sea will be gone, replaced by a Himalayan-scale mountain belt running through what is now southern Europe.

Australia’s northward migration will crumple the islands of Indonesia and New Guinea into a major mountain chain. Meanwhile, the mid-ocean ridges that are currently spreading the Atlantic floor may slow or stall, and new subduction zones could develop along the Atlantic’s margins. Each of these tectonic rearrangements reshapes not just elevation but coastlines, river systems, and climate patterns on a continental scale.

Sea levels will also shift. In the geological past, changes in ocean-floor spreading rates and the volume of mid-ocean ridges have caused seas to rise and fall by enormous amounts. During the Late Cretaceous, about 80 to 90 million years ago, sea level stood roughly 170 meters higher than today, largely because vigorous spreading ridges displaced more ocean water onto the continents.⁵ Whether the future brings higher or lower seas depends on the pace of spreading and subduction. If spreading slows as the next supercontinent assembles, ridges shrink in volume, ocean basins deepen, and sea levels could fall, exposing broad continental shelves. If new spreading centers open elsewhere, the reverse could happen. Either way, the coastlines of 100 million years hence will bear no resemblance to today’s.

A Slightly Brighter Sun

The Sun is not a static light bulb. It has been gradually brightening since its formation, and it will continue to do so. The current rate of increase is about one percent every 110 million years.⁶ That means at the 100-million-year mark the Sun will be almost exactly one percent more luminous than it is now. One percent sounds trivial, and on its own it is. But it adds up over geological time, and it interacts with other factors, especially greenhouse gases and continental configuration, that amplify the warming.

Climate modeling of Earth under gradually increasing solar output shows that for small increases (up to about ten percent), the planet warms in a fairly predictable, linear way. The trouble starts later, around a twelve-and-a-half percent increase in solar output, when the atmosphere undergoes a fundamental shift in its radiative-convective state and global mean surface temperatures jump above 330 K (roughly 57 °C).⁷ That catastrophic threshold is still about a billion years away. At 100 million years, the direct solar forcing alone adds only modest warmth, perhaps a degree or two Celsius globally. The larger question is what the rest of the climate system does with that extra energy.

The Carbon Cycle and a Hotter Interior

Earth’s long-term thermostat is the silicate weathering cycle: rain dissolves rocks, the dissolved minerals react with carbon dioxide, and the carbon gets buried on the seafloor as carbonate minerals. This process draws CO₂ out of the atmosphere over hundreds of thousands of years, keeping temperatures from spiraling out of control. On 100-million-year timescales, this feedback loop is the dominant control on atmospheric CO₂.⁸

But the thermostat is not perfect, and it depends heavily on geography. When continents gather into a supercontinent, the vast interior regions sit far from moisture sources. Reduced rainfall means less chemical weathering, which means less CO₂ is pulled from the air. Modeling of the next supercontinent assembly found that reduced moisture reaching continental interiors creates large arid zones where surface runoff drops to near zero, weakening the carbon sink and allowing atmospheric CO₂ to climb.⁹ At the same time, volcanism along new subduction zones and from mantle plumes can pump additional CO₂ into the atmosphere. The deep carbon cycle is complex: current models suggest that less than five percent of the carbon involved in mantle magmatic processes actually reaches the surface, but the fraction that does escape matters enormously for the atmosphere.¹⁰

So 100 million years from now, the climate will reflect a tug-of-war: a marginally brighter Sun pushing temperatures up, weathering trying to pull them down, and continental arrangement tilting the playing field. If the continents are mid-assembly and large interior deserts have already formed, the planet could be warmer than today even without any human influence.

Oceans Rerouted

Continental drift does not just move landmasses; it rearranges the plumbing of the entire ocean. Today’s global ocean circulation depends on the specific arrangement of continents, ocean gateways, and basin geometries. Close a gateway, and deep-water currents change direction; open one, and new circulation patterns emerge. The South China Sea offers a useful case study: as plate convergence gradually altered the Luzon Strait over the past ten million years, surface circulation reversed direction and deeper flows reorganized.¹¹

Scale that up to a global continental rearrangement and the implications are enormous. If the Atlantic narrows, the Atlantic Meridional Overturning Circulation that currently distributes heat to northern Europe will weaken or disappear. If Australia seals off passages between the Indian and Pacific oceans, tropical heat distribution changes fundamentally. The opening and closing of ocean gateways has historically triggered ice ages and hothouse periods alike. At 100 million years, whichever ocean is closing will be producing a cascade of circulation changes that alter regional climates, nutrient delivery, and marine productivity worldwide.

The relationship between sea level and marine sedimentation adds another dimension. Geological records show that when sea levels are low, chemical erosion of exposed continents increases, and sediment accumulation in ocean basins rises.¹² The future ocean, shaped by new basin geometries and altered erosion patterns, will deposit sediments in completely different places and at different rates, reshaping the seafloor itself.

Longer Days, a More Distant Moon

Earth’s rotation is gradually slowing because the Moon’s gravity creates tidal bulges that act as a brake. The Moon, in turn, spirals outward. Over the next 100 million years, the day will lengthen by roughly half an hour to an hour. That may sound minor, but it has cascading effects: slower rotation means weaker Coriolis forces, which affects the width and number of atmospheric jet streams and the strength of storm systems. Ocean tides will also change, not just because the Moon is farther away, but because basin geometry shifts as continents move. Tidal dissipation models integrated billions of years into the future suggest that oceanic tidal energy dissipation will generally decrease for most of Earth’s remaining lifespan.¹³

Weaker tides could have biological consequences. Intertidal ecosystems, which depend on the rhythmic exposure and submersion of coastlines, would shrink. Tidal mixing, which brings nutrients from the deep ocean to the surface, would diminish in some regions. Combined with the rearranged ocean basins, the marine world of 100 million years hence could look profoundly different from today’s.

Mantle Plumes and Volcanic Surprises

Earth’s interior is not sitting still either. Mantle convection drives both plate tectonics and a less predictable phenomenon: mantle plumes, which are upwellings of hot material from deep in the mantle that can produce massive volcanic events at the surface. When a plume arrives beneath a continent, the surface uplifts by half a kilometer to two kilometers within a few million years, often followed by enormous flood-basalt eruptions.¹⁴ These Large Igneous Provinces have repeatedly reshaped Earth’s surface, triggered mass extinctions, and broken apart continents.

Predicting exactly where plumes will surface 100 million years from now is impossible, but the underlying mantle dynamics are persistent. Convection models show that mantle flow generates dynamic topography across a wide range of scales, from features smaller than 500 km to swells spanning more than 10,000 km.¹⁵ These deep-mantle signals warp the surface gently but persistently, causing regions to rise or sink by hundreds of meters over tens of millions of years. Historical records confirm the pattern: plume arrivals beneath Gondwana, Europe, and Africa each left distinctive gaps in the sedimentary record as the surface rose and erosion dominated.¹⁶ Whatever new supercontinent is assembling, its surface will be warped by plumes and convection currents that no surface map can capture alone.

Life Will Be Unrecognizable

If the physical planet changes this much, the life on it will change at least as drastically. One hundred million years is enough time for entirely new classes of organisms to evolve and for familiar ones to vanish. For perspective, 100 million years ago dinosaurs dominated every continent, flowering plants were just beginning to diversify, and mammals were small, marginal creatures. The evolutionary distance between then and now gives a rough sense of how different the biosphere could become.

Studies of biodiversity through deep time show that the diversity of major groups follows rise-and-fall trajectories. Species within a group tend to become increasingly vulnerable to extinction and less likely to give rise to new species as time goes on; the groups that endure are those that produce lineages capable of bucking that trend.¹⁷ Which groups are dominant 100 million years from now depends on which environmental pressures they face, and the rearrangement of continents will create entirely new selective landscapes: new climate zones, new ocean currents distributing nutrients, new mountain barriers isolating populations.

The modeling study on the next supercontinent assembly paints a particularly sobering picture for land mammals. As continents converge, expanding arid interiors and elevated CO₂ could produce heat extremes that push many mammal species past their physiological limits.⁹ Whether mammals survive that bottleneck, adapt, or are replaced by something else is a question evolutionary biology can frame but not answer in advance.

Orbital Stability Is Not a Concern

One worry you might have about 100-million-year timescales is whether Earth’s orbit itself will remain stable. The solar system is technically chaotic, meaning tiny differences in starting conditions can lead to wildly different outcomes over billions of years. But an ensemble of 1,600 high-precision simulations of the solar system’s future, run over five billion years, found that none produced a destabilization of Earth’s orbit or a close encounter involving our planet.¹⁸ Earth will continue circling the Sun on a well-behaved path. The drama is all happening on the surface and in the interior, not in the orbit.

What Remains of Us

It is natural to wonder whether any trace of human civilization would survive 100 million years of plate tectonics, erosion, subduction, and metamorphism. The answer is: probably very little, and only in specific geological settings. Researchers studying what they call “technofossils,” the preservable material remains of human technology, point out that the sheer diversity of objects we produce already exceeds known estimates of biological fossil diversity.¹⁹ But diversity of form does not guarantee survival in the rock record. Most of the technosphere sits on the surface, where erosion destroys it within thousands of years. Only materials that get buried in sedimentary basins and happen to avoid subduction have a chance of persisting.

The concept of “technostratigraphy,” a new kind of geological layering defined by human artifacts rather than natural sediments, highlights just how concentrated in time and space our impact is.²⁰ In 100 million years, that layer will be compressed to a thin, chemically anomalous band in whatever sedimentary rocks survive. A future geologist, if one existed, might detect unusual concentrations of certain synthetic materials, isotopic anomalies from nuclear testing, or a sharp spike in carbon isotope ratios from fossil-fuel burning. But recognizable objects, buildings, roads, even plastics, will long since have been destroyed or metamorphosed beyond recognition. The most durable legacy of human civilization may be an isotopic fingerprint no thicker than a pencil line in the rocks.