The study provides new, sharp evidence of early plate tectonics flipping the geomagnetic poles
New research analyzing the oldest pieces of rock on the planet at least 3.25 billion years ago adds some poignant evidence of Earth's crust pushing and pulling, similar to modern plate tectonics. The study also provides the first evidence of when the planet's magnetic north and south poles switched.
Both results provide clues as to how such geological changes could lead to a more favorable environment for the development of life on the planet.
Using novel techniques and instruments, researchers show that Earth's early surface moved at a rate of 6.1 centimeters per year and 0.55 degrees per million years.
That speed is double the rate the same researchers showed in a previous study that the ancient crust was moving. Both the speed and direction of this latitudinal motion leave plate tectonics as the most logical and robust explanation for it.
There's a lot of work that suggests plate tectonics wasn't actually the planet's main way of releasing internal heat by shifting plates early in Earth's history said Brenner Ph.D. This evidence allows us to more confidently rule out explanations unrelated to plate tectonics.
For example, researchers can now argue against true polar wander and phenomena known as stagnation lid tectonics. Both of these cause the Earth's surface to change but are not part of modern style plate tectonics. The results tend to favor plate tectonic motion because the newly discovered high speed is different from the elements of the other two processes.
The paper contains what scientists believe is the oldest evidence of when Earth reversed its geomagnetic fields. That is, the positions where the magnetic north and south poles are reversed. This flip flop is a common occurrence in Earth's geologic history. According to NASA the pole has flipped 183 times in the last 83 million years and probably several hundred times in the last 160 million years.
The reversal says a lot the planet's magnetic field 3.2 billion years ago. Chief among these implications is that the magnetic field is stable and strong enough to keep the solar wind from degrading the atmosphere. This insight, combined with findings on plate tectonics, provides evidence for the conditions under which the earliest forms of life evolved.
In Brenner's words it paints this picture of an early Earth that was already geodynamically mature. It has a wide variety of dynamic processes that result in Earth having more stable environmental and surface conditions that make it more possible for life to develop and thrive. Said that.
Today Earth's outer shell consists of 15 shifting blocks of crust or plates that contain the planet's continents and oceans. Over the ages the plates move and separate from each other to form new continents and mountains and expose new rocks to weather. This led to chemical reactions that stabilized Earth's surface temperature over billions of years.
Evidence of when plate tectonics began is difficult to find because ancient pieces of crust are pushed into the inner mantle. Never to be seen again. Only five percent of all rocks on Earth are older than 2.5 billion years. No rock is older than four billion years.
Overall, the study adds to a growing body of research showing that tectonic movements occurred relatively early in Earth's 4.5 billion-year history and that the earliest forms of life appeared in more temperate environments. Project members revisited the Pilbara Craton. It stretches for about 300 miles. Back in Cambridge they drilled into a primitive and thick slab of crust there to collect samples that were analyzed for their magnetic history. Intuition Creatures
Story Source:
Materials provided by Harvard University. Original by Juan Silizar.
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