Explain about jigsaw puzzle &moving plates
Answers
Answer:
The biggest jigsaw puzzle in the solar system has a split personality: The number and sizes of Earth's tectonic plates can flip, according to a new study.
Today, the pieces of Earth's broken shell are unequal in size. Of about 50 plates, a mere seven account for 94 percent of the surface. The biggest, the Africa and the Pacific plates, are antipodal, meaning they sit on opposite sides of the Earth.
But about 100 million years ago, the tectonic plates tiled the planet as evenly as a real-life jigsaw puzzle.
"The distribution of the large plates has not always been the same," said lead study author Gabriele Morra, a geodynamicist at the University of Louisiana in Lafayette. "The large plates have really oscillated between different patterns. This has strong implications for what is driving Earth's mantle convection," Morra told LiveScience's OurAmazingPlanet.
Morra also found that the number of small plates was about the same for the past 60 million years. "This means that if you want to understand Earth's evolution, the interesting part is the large plates," Morra said. "The large plates will tell us what's really going on."
Earth's alternating plate engine
Plate tectonics theory holds that Earth's crust is divided into plates, which move across the underlying mantle at a rate of inches (centimeters) a year. The model helps explain Earth's changing surface now and in the past, from the tallest mountains to the deepest earthquakes. But geoscientists actively debate whether the slow shuffle of tectonic plates comes from either pulling by sinking slabs of crust or pushing by convection currents in the hot, rocky mantle — or both. [Infographic: Tallest Mountain to Deepest Ocean Trench]
Plates1
Tectonic plate sizes in Earth's past 200 million years. Darker gray indicates larger plate size.Gabriele Morra
Morra and his colleagues put together a detailed reconstruction of Earth's plates for the past 200 million years. To explain the switch in plate sizes, they suggest Earth's plate tectonic engine may alternate between the plate- and mantle-driven models.
When large plates dominate, then "top-down" tectonics prevails, with big, sinking plates running the show, the researchers said. This was the case about 200 million years ago, when the supercontinent Pangaea covered the planet. It's also today's tectonic setting, with the giant Pacific plate diving down into the mantle. But when the puzzle pieces are evenly spaced, then "bottom-driven" mantle forces dominate, the researchers said. Computer models of bottom-driven convection produce similar results, Morra said. "When you do these experiments, you tend to have this constant plate size," he said.
"I think what this work helps us understand is that plate tectonics is not simply driven by one process," Morra said. "Clearly this poses more questions than answers, but it reinforces the view that the Earth goes through radical global changes," he said.
Answer:
Given by Alfred Weber in his continental drift theory in 1912.
Explanation:
- The Jigsaw fit was one of the most interesting pieces of evidence that Wegener gave to explain his theory and thus concluded that the continental landmasses had drifted 100 million years ago to form the represent known landmass and thus the evolution of the present life forms on earth.
- The puzzle was made by fitting the coastal zones of eastern Africa with those of southern America's as the landmass was made by the Gondwana period of the super-landmasses that had an evolutionary cycle. And according to Wegner drifted at a sped of 250 cm peryear.
I hope it helps you ☺️