Where Was Your Town 200 Million Years Ago? The Science Behind the ‘Ancient Earth’ Globe

Quick answer: Ancient Earth is a free interactive 3D globe at dinosaurpictures.org/ancient-earth, built by software developer Ian Webster. You type in a city or address, pick a moment between today and 750 million years ago, and the globe shows roughly where that spot sat on the planet’s shifting continents. It does not simulate geology itself. It places your location on published paleogeographic maps by geologist Christopher R. Scotese from the PALEOMAP Project, the same reconstructions that are distributed as a plate model for the open-source scientific software GPlates. The results are approximate: the site itself says locations are accurate to within about 100 kilometres, and different scientific models can disagree.

The globe goes viral every few years because it answers a question almost everyone has wondered about: where was my home when dinosaurs were alive? Here is how it works, what science sits underneath it, and how much you should trust what it shows you.

What the Ancient Earth globe does

The site opens on a rotating globe with a time menu that runs from the present day back to 750 million years ago, plus shortcuts to key moments such as the first green algae, the supercontinents Pannotia and Pangea, and the extinction of the dinosaurs. Colours show elevation and water depth: darker blues for deep ocean, lighter blues for shallow seas, then greens, tans, browns and white for progressively higher land.

Enter a location and a marker appears on the ancient map. Explaining the tool to CNN in 2020, Webster said: “My software ‘geocodes’ the user’s location and then uses (Scotese’s) models to run their location backwards in time.” The map can also list dinosaurs known to have lived nearby, drawing on the Dinosaur Pictures database that Webster runs on the same site.

Webster also pointed out some of the surprises the globe reveals for North America: “the US used to be split by a shallow sea, the Appalachians used to be very tall mountains comparable to the Himalayas, and that Florida used to be submerged.”

The science underneath: plate tectonics

Earth’s outer shell is broken into rigid tectonic plates that move slowly over the hotter, weaker mantle below. According to the U.S. Geological Survey’s guide to plate tectonics, plates separate at mid-ocean ridges at rates ranging from less than 2.5 centimetres a year on the Arctic Ridge to more than 15 centimetres a year on the East Pacific Rise. That sounds trivial, but over 100 to 200 million years it has opened the entire Atlantic Ocean from a narrow inlet between Europe, Africa and the Americas.

The idea has a long history. As the USGS explains, the German meteorologist Alfred Wegener proposed continental drift in 1912, arguing that the supercontinent Pangaea had split apart. Pangaea began breaking up about 225 to 200 million years ago, eventually forming the continents we know today. Plate tectonics, which explained the mechanism Wegener lacked, took shape in the 1960s.

How geologists rebuild a map of the past

No one can observe a continent’s position 300 million years ago directly, so reconstructions combine several independent lines of evidence:

• Ancient magnetism. Some rocks record the direction of Earth’s magnetic field when they formed, which reveals the latitude where they formed. It says much less about longitude, one reason older maps carry more uncertainty.
• The ocean floor. Magnetic stripes and the ages of seafloor rocks record how fast oceans opened. Because old ocean floor is gradually recycled back into the mantle at subduction zones, this record fades for the more distant past.
• Fossils and rocks. Matching fossils, mountain belts and rock formations on now-separate continents show which pieces used to fit together, while coal, reefs, desert sandstones and glacial deposits indicate past climates and latitudes.

Who made the maps: Scotese, PALEOMAP and GPlates

The globe’s maps come from Christopher R. Scotese, a geologist who has spent decades producing global reconstructions of Earth’s geography through the PALEOMAP Project. The site credits him directly: “Paleogeographic maps by C.R. Scotese, visualization developed by Ian Webster.”

Scotese’s work is available to researchers as the PALEOMAP PaleoAtlas for GPlates, hosted by the EarthByte group at the University of Sydney. It contains 91 paleogeographic maps covering the Phanerozoic eon, the last roughly 540 million years, and the late Neoproterozoic before it, and it can be loaded into GPlates.

GPlates is free, open-source desktop software for interactive visualisation of plate tectonic reconstructions through geological time. Researchers use it, and its Python library pyGPlates, to move continents, coastlines, fossil sites and other data back through time according to a chosen plate model. Ancient Earth applies the same basic idea to a single point: your address.

How accurate is it?

Treat the globe as a well-informed sketch, not a GPS reading of the past. The site states that locations are accurate to about 100 kilometres, and that clouds and the starry background are not adjusted for the time period shown. Webster himself has urged caution. In a 2018 discussion quoted by ScienceAlert, he wrote that users should “consider the plots approximate,” that “model results can vary significantly,” and that he chose this model “because it is widely cited and covers the greatest length of time.”

Uncertainty also grows the further back you go. Reconstructions of the last 200 million years can draw on surviving ocean floor, but maps of the deep Precambrian rely much more heavily on scattered magnetic and rock evidence, so the earliest views on the globe are the most tentative. The featured image above, for example, was made with GPlates using a different published plate model, so its outlines may differ in detail from Scotese’s maps of the same period.

The ground beneath us has a long and restless history. Read how the Witwatersrand Basin produced nearly half the world’s gold, how scientists found a vast water reservoir hidden deep beneath Earth’s surface, why deep-sea minerals from off Oregon burst into flames in a USGS lab, and what happened during the Shinmoedake eruption in southern Japan. Find more in our Science section.

Frequently asked questions

What is the Ancient Earth globe?

It is a free interactive 3D globe at dinosaurpictures.org/ancient-earth, created by Ian Webster, that shows how Earth’s continents were arranged at different times over the past 750 million years and lets you find where any address would have been.

Where does the Ancient Earth globe get its maps?

From paleogeographic reconstructions by geologist Christopher R. Scotese and the PALEOMAP Project. The same maps are distributed as the PALEOMAP PaleoAtlas for GPlates, the open-source plate tectonics software used by researchers.

How accurate is Ancient Earth?

The site says locations are accurate to about 100 kilometres. Its creator describes the results as approximate, since different scientific models can disagree, especially for the distant past.

How fast do continents move?

According to the USGS, plates separate at mid-ocean ridges at anywhere from less than 2.5 centimetres a year to more than 15 centimetres a year. Over millions of years, that adds up to thousands of kilometres.

When did Pangaea break apart?

The USGS says the supercontinent Pangaea began to break up about 225 to 200 million years ago, eventually forming today’s continents.

Sources: Ancient Earth, dinosaurpictures.org; EarthByte, PALEOMAP PaleoAtlas for GPlates; GPlates; U.S. Geological Survey, This Dynamic Earth: Historical perspective and Understanding plate motions; CNN (2020); ScienceAlert.

Featured image: Reconstruction of Pangaea about 200 million years ago, made with GPlates. Map by Fama Clamosa, CC BY-SA 4.0, via Wikimedia Commons.