A geological reorganization near Japan more than 10 million years ago appears to have accelerated the formation of the Gulf of California, creating the outlet that allowed the Colorado River to carve the Grand Canyon, according to a study published Oct. 29 in Science.
The Gulf of California is an example of a rift zone, a place where continental crust pulls apart and creates a low spot that can fill with ocean water. But rifting can slow, speed up or stop entirely. In the Gulf of California, rifting not only persisted but sped up, taking about 6 million to 13 million years, much quicker than the typical span of 30 million to 80 million years.
Study co-author Guido Gianni, a geophysicist at the Czech Academy of Sciences, wondered why. No previous research had fully explained the rapid rifting, which transferred the Baja California peninsula to the Pacific Plate and provided an outlet for the developing Colorado River, which subsequently carved the Grand Canyon on its way to sea level.
Gianni and co-author Thorsten Becker, a geophysicist at the University of Texas at Austin (UT Austin), along with UT Austin doctoral student Xiang He, used a global model of plate tectonics run on supercomputers at the Texas Advanced Computing Center to see whether far-flung forces might provide an explanation.
Around the same time the Gulf of California was pulling apart, Japan was undergoing its own geological changes. About 10 million to 12 million years ago, a single subduction zone near Japan transitioned into two separate subduction zones. This transition at the western end of the Pacific Plate influenced tectonic forces on the other side of the plate, He, Gianni, Becker and their colleagues found.
"It turned out — ta-da! — [with] the change in this pulling stress, Baja California was one of the few places outside the Japan region that were affected," Becker told Live Science. It was "unexpected and sort of a little bit too good to be true." The researchers tweaked their model to see if the result held with different assumptions about stresses and mantle properties, and it did.
The Gulf of California was already rifting regardless of the situation across the Pacific. The initial rift was caused by the subduction of a tectonic plate called the Farallon Plate, under the West Coast of North America. But such rifting might have ended with little more than a small valley or low spot if Japan's influence had not kicked in to give the rifting extra force.
Becker noted the findings have direct implications for understanding how plate boundaries form. "It's more than a regional curiosity," he said. "It's a reminder of the global connectedness of mantle convection and plate tectonics."
The research could also affect understanding of earthquake-generating faults such as the San Andreas in California and the Cascadia subduction zone in the Pacific Northwest, Becker said. "If I'm asking what is the mantle doing underneath Cascadia so I get our megathrust correct," he said, "I need to include these effects."
Analysis
Why This Matters
- The study reveals that tectonic events on one side of a plate can influence geological features thousands of kilometres away, showing the global connectedness of plate movements.
- It explains why the Gulf of California opened much faster than typical rift zones, a puzzle that had not been resolved by regional explanations alone.
- Understanding the forces that shaped the region's crust helps scientists model stress on active earthquake faults such as the San Andreas and the Cascadia megathrust, which are capable of magnitude 9 or larger quakes.
Background
The Gulf of California began to form when the Farallon Plate subducted under North America, stretching and thinning the continental crust. About 6 to 8 million years ago, the Baja California peninsula separated from mainland Mexico as rifting accelerated. The resulting low corridor allowed the Colorado River to reach the Pacific Ocean; as the river cut downward through the Colorado Plateau, it carved the Grand Canyon. Until now, geologists lacked a clear explanation for why the rifting happened so quickly.
What to Watch
- Whether further modelling of stress transfer across plates can refine hazard assessments for the San Andreas Fault and the Cascadia subduction zone.
- Additional studies testing similar far-field influence on other rift zones around the world, such as the Red Sea.
- Potential updates to global plate-tectonic models that incorporate the effect of subduction-zone geometry changes on distant boundaries.
Checked
10 claims in this story checked against 1 source: 10 supported.
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- SupportedA tectonic shift near Japan helped set the stage for the Grand Canyon.Latest from Live Science: “This reorganization led to a transfer of tectonic force across the Pacific tectonic plate, which, in turn, opened the Gulf of California and ultimately led to the Grand Canyon's formation”
- SupportedA double subduction zone off Japan transferred stress across the Pacific and accelerated Gulf of California rifting.Latest from Live Science: “The birth of the Gulf of California... was accelerated by the formation of a double subduction zone more than 6,000 miles (9,600 kilometers) away, near Japan. This reorganization led to a transfer of tectonic force across the Pacific tectonic plate”
- SupportedThe Gulf of California rifting created an outlet for the Colorado River, which later carved the Grand Canyon.Latest from Live Science: “it provided an outlet for the developing Colorado River, which subsequently carved the Grand Canyon on its way to sea level.”
- SupportedThe study was published Oct. 29 in Science.Latest from Live Science: “according to new research published Oct. 29 in the journal Science .”
- SupportedGulf of California rifting took about 6 million to 13 million years, compared with a typical 30 million to 80 million years.Latest from Live Science: “Rifting took about 6 million to 13 million years — much quicker than the typical speed of 30 million to 80 million years.”
- SupportedAbout 10 million to 12 million years ago, one subduction zone near Japan became two.Latest from Live Science: “About 10 million to 12 million years ago, a single subduction zone near Japan transitioned into two separate subduction zones.”
- SupportedThe researchers found that the change near Japan influenced tectonic forces on the other side of the Pacific Plate.Latest from Live Science: “This transition at the western end of the Pacific Plate influenced the tectonic forces on the other side of the plate, He, Gianni, Becker and their colleagues found.”
- SupportedBecker said Baja California was one of the few places outside Japan affected by the change in pulling stress, and described the result as unexpected.Latest from Live Science: “"It turned out — ta-da! — [with] the change in this pulling stress, Baja California was one of the few places outside the Japan region that were affected," Becker said. It was "unexpected and sort of a little bit too good to be true."”
- SupportedThe Gulf was already rifting, but Japan's influence may have given it extra force and prevented the rifting from ending as a small valley or low spot.Latest from Live Science: “The Gulf of California was already rifting regardless of the situation across the Pacific... such rifting might have ended with nothing more than the formation of a little valley or low spot if Japan's influence had not kicked in to give the rifting some extra oomph.”
- SupportedBecker said the findings could have implications for understanding earthquake-generating faults including the San Andreas and Cascadia zones.Latest from Live Science: “The findings could have implications for understanding earthquake-generating faults such as the San Andreas in California and the Cascadia subduction zone in the Pacific Northwest, Becker said.”