A Virginia Tech team of geologists have traced how continents were generated on Earth more than 2.5 billion years ago and continued till 70 million years ago affecting the planet’s life, climate and the landscape.
Published in Nature Geoscience, the study focused on recent geologic events such as volcanic activity 10 million years ago in what is now Panama and Costa Rica to reveal the secrets of the continent-building.
“Without continental crust, the whole planet would be covered with water,” said Esteban Gazel, an assistant professor of geology with Virginia Tech’s College of Science. Unlike other planets in the solar system, the continental masses or areas of buoyant, thick silicic crust are a unique characteristic of Earth, he noted.
The continental mass of the planet formed in the Archaean Eon, about 2.5 billion years ago when the Earth was three times hotter with high volcanic activity, perhaps making it unviable for any organism to survive.
In the past, many scientists believed that the planet’s continental crust was generated during this time in Earth’s history, and it recycles through collisions of tectonic plates. But the new research, for the first time, shows that a “juvenile” continental crust has been produced throughout Earth’s history.
Setting aside the mystery of the Earth undergoing recycling of its continental crust, Gazel said: “We were able to use the formation of the Central America land bridge as a natural laboratory to understand how continents formed, and we discovered while the massive production of continental crust that took place during the Archaean is no longer the norm, there are exceptions that produce ‘juvenile’ continental crust.”
The researchers used Costa Rica and Panama, which were formed when two oceanic plates collided and melted iron- and magnesium-rich oceanic crust over the past 70 million years. It produced what today are the Galapagos islands, reproducing Achaean-like conditions to provide the “missing ingredient” in the generation of continental crust, said Gazel.
The researchers discovered that erupted lavas reached continental crust about 10 million years ago, based on their survey of volcanoes from oceanic arcs, where two oceanic plates interact. The western Aleutian Islands and the Iwo-Jima segment of the Izu-Bonin islands of are some other examples of juvenile continental crust, the researchers said.
However, some interesting questions raised by the study include further investigation as to how the continental crust has had impacted the evolution of not just continents, but life itself.
For instance, the formation of the Central American land bridge resulted in the closure of the seaway, which changed how the ocean currents, separated marine species, and had a powerful impact on the climate on the planet.
“We’ve revealed a major unknown in the evolution of our planet,” said Gazel, whose team consisted of Eric Vance, an assistant research professor of statistics in Virginia Tech’s College of Science, and statistics graduate student Shuyu Chu of Ruzhou, China.
Researchers from the University of Wyoming, the GEOMAR Helmholtz Center for Ocean Research in Kiel, Germany, the Lamont-Doherty Earth Observatory of Columbia University, Simon Fraser University in Canada, Rutgers University, and University of South Carolina also contributed to the study.