Underground movement

The devastating tsunami of 2004 focused international attention on the shifting of major landmasses—a subject for which Professor Chris Scotese is known worldwide

Computer simulation of plate motions
The sequence of maps from a computer simulation by Professor Chris Scotese illustrates plate motions and sea level changes during the last 400 million years.

Chris Scotese calls himself an Earth historian, a maker of maps that illustrate how geography and climate have changed the planet over millions of years.

“It’s the scientific equivalent of inventing a time machine,” says Dr. Scotese, a professor in The University of Texas at Arlington’s Department of Earth and Environmental Sciences.

His mapmaking interest traces to a childhood fascination with dinosaurs. As an undergraduate in the 1970s, his focus turned to biogeography, the study of how animal life has been distributed on Earth throughout its history. But he couldn’t find maps that showed how plate movements affected this distribution.

So he created his own.

“My generation was the first to be taught about plate tectonics as undergraduates,” he says. “This theory had only been around for about six years at the time I became interested in making maps showing the movements of the continents.”

According to plate tectonics, Earth’s outermost layer, the lithosphere, divides into seven large crustal blocks and several minor crustal blocks called plates. Scientists recognized that these plates existed from information gathered during the 1960s and ’70s about the nature of the ocean floor, Earth’s magnetic forces, the location and distribution of volcanoes and the heat flow from Earth’s interior core, and the distribution of fossils worldwide.

The plates are in constant flux, moving in different directions and at various speeds. The distance they move ranges from two centimeters to 10 centimeters annually—about the speed that human hair or nails grow.

Although they travel slowly, the plates move with great force, at times crashing into and scraping past each other, much like cars in a demolition derby. Where the plates collide and one moves beneath the other is called a subduction zone. Result: earthquakes.

When this happens, land is raised up. The Himalayas, for example, resulted from the collision of India with Asia. Earthquakes like those that recently occurred in Indonesia are the result of the subduction of the Indian Ocean beneath the islands of Sumatra and Java.

Volcanic action under the ocean adds newly molten lava to the seafloor at the places where plates meet, causing the oceans to widen where the new material erupts. When landmasses drift apart, the separating plates carry them away. The Atlantic Ocean was created this way.

As a result of the ongoing plate movement, Earth’s geography is constantly, slowly changing. Viewed over millions of years, the changes are considerable, affecting the distribution of plant and animal life.

Tsunamis, earthquakes and volcanic eruptions
Scotese is reconstructing the tectonic history of the Pacific plate. He and Professor Michelle Kominz of Western Michigan University have received a $250,000 National Science Foundation grant for the study.

“The Pacific Ocean, which is the largest ocean, lies above one of the largest and oldest plates, the Pacific plate,” Scotese explains. “Because the Pacific plate is so large and so old, it has had a tremendous impact on Earth history. It played a role in the formation of both the Rocky Mountains and Andes Mountains, and changes in how fast it moves have caused sea level fluctuations that sometimes exceeded 200 meters.” 

His maps show how plate tectonic movements have formed and broken apart continents, created mountains and oceans, and been responsible for earthquakes, volcanic activity—and tsunamis.

Numerous media outlets sought out Scotese following the tsunami that struck Dec. 26, 2004, in the Indian Ocean. The undersea earthquake was among the deadliest disasters in modern history, killing more than 200,000 people.

“The process that triggers a tsunami is the same subduction process that forms mountains and volcanoes,” he says. “My maps show how subduction has been going on in that area for hundreds of millions of years—earthquakes are not unusual there.”

Geologists know that earthquakes occur along subduction zones but can’t predict the conditions that will cause a tsunami. Warning systems that alert to a potential tsunami following an earthquake have been implemented in the Pacific Ocean region, where most of the plate tectonic/earthquake activity occurs. But funding hasn’t been available for such a system for the Indian Ocean countries. Scotese says that since the 2004 tsunami, the United Nations is considering funding a system for the region.

Unlike major earthquakes or tsunamis, scientists are better able to predict volcanic eruptions because the movement of magma beneath the volcano triggers swarms of small earthquakes that have a distinctive seismic pattern.

“Mount St. Helen’s has gotten a lot of attention during the past 20 years, but there’s a larger volcano under Yellowstone National Park,” Scotese says. “The hot springs are warmed by molten material below the surface.”

Although the volcanic activity beneath Yellowstone is large, there’s apparently no danger of an eruption any time soon.

“According to scientific research, the volcano below Yellowstone National Park has erupted three times during the past two million years. That’s about once every 600,000 years.”

Though the last major eruption was about 600,000 years ago and another is due, Scotese says not to worry. “The error margins on these calculations are thousands of years.”

High-tech maps teach millions
Scotese’s undergraduate research coincided with the early use of mainframe computers. The first software he developed to make plate tectonic maps, or “paleomaps,” utilized Fortran programs on punch cards. His lifetime of research evolved into the Paleomap Project, which is recognized worldwide as a resource for students and teachers of Earth history.

Today, at www.scotese.com, full-color 3-D interactive computer animations depict Earth’s history. Rotating globes show the ancient mountain ranges and shorelines, active plate boundaries and the extent of paleoclimatic belts. Each era can be viewed separately, and the science behind the maps and animations is explained.

The globes can be manipulated, rotated and seen from different angles. For two years, Scientific American has selected the Web site as one of the Fifty Best Science Education sites in the world. In the past six years, it has welcomed more than 30 million visitors.

“Dr. Scotese’s work is known everywhere in the world. Everybody who examines these kinds of problems uses his maps,” said Robert Stern, professor and head of the Department of Geosciences at UT Dallas. “He’s interested in showing the planet the way it would look to a time traveler who came back and looked at Earth’s surface. He shows what the surface really looked like.”

Dozens of museums feature Scotese’s maps, including the Smithsonian in Washington, D.C., the American Museum of Natural History in New York, the Field Museum in Chicago and museums in Europe and Asia, as well as the Dallas Museum of Natural History and Fort Worth Museum of Nature & Science. His work has been featured on PBS, BBC and National Geographic Television specials and in the most recent version of the National Geographic Atlas of the World.

He has written or co-written more than 100 scientific papers and is working on a book, The Atlas of Earth History. Educators, students, fellow researchers and geologists consult Scotese for advice about paleogeographic reconstructions. He has helped several universities, including The University of Texas at Austin (Institute for Geophysics), the University of Chicago and the University of Sydney in Australia, establish similar paleomap programs.

His most recent research concerns global climate change and paleoclimate. The maps at his Web site clearly show how Earth has alternately been in an “Ice House,” like today’s world where there’s ice at the poles and a “Hot House,” like the time of the dinosaurs when tropical plants grew in the Arctic Circle.

Recent climate simulations, done in collaboration with the Argonne National Laboratory in Illinois, compare and contrast the Ice House climate that prevailed 300 million years ago with the Hot House climate of 90 million years ago.

“These studies have a lot to tell us about our current climatic predicament,” Scotese says. “All the scientific evidence points to the fact that manmade changes may be quickly shifting Earth from its Ice House state to a Hot House state, similar to the climate that existed when the dinosaurs were around.”

— Kim Pewitt-Jones

Phyllis Richmond contributed to this article.