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Viewings: 4203The rhythm of the climatic changes that occurred during the past millions of years of Earth's history, is determined by the orbital cycles: depending on the amount of sunlight glaciers grow or recede. Changes speaks the whole planet - from circulation of the atmosphere and ocean to ecosystems and even erosion and sediment transfer.
New research suggests that it affects the volcanism. Scientists before seen such correlation for limited periods of time and on a regional scale, and the new work gives a broader picture.
To get a long record of volcanic eruptions, the researchers took up the seafloor sediments from around the Pacific ring of fire. Unlike the land, where there is no erosion, destroying the layers of ash. Dating layers is performed by comparing them to reliably dated ground layers and assess the rate at which sediment accumulate on the seabed. The error is of course inevitable, but the researchers did everything possible to account for uncertainty.
By bringing together data about all the eruptions of the last million years, experts have found the cycles of the same duration as the orbital. Most visibly manifested cycle tilt axis duration 41 thousand years. To check was generated 100 thousand random data sets. Less than 1% of them gave a correlation corresponding strength of the evidence.
But why? Rather, the point in changes of stress in the earth's crust caused by the ice ages and interglacials. Ice sheets have taken a toll on the bark beneath them, and the falling of the sea level accordingly change the state of health of the oceanic crust. And Vice versa. Take a ball or a balloon, and push in one place: you will see how this is expending its surface at a different point. Therefore, when sea level rise (and increasing pressure on oceanic crust) is slightly raised and continental crust (for example, in volcanically active areas of Central and South America). This reduces the upper pressure in magmatic chambers, and the magma easier to get out.
To test the hypothesis, the researchers took advantage of a simple computer model of stressed state of the earth's crust during the last glaciation in Central America. Correlation eruptions with the calculated stress was very beautiful.
In General, the peak of volcanic activity on several thousand years behind changes the axis tilt (and climate). It's normal to the earth's crust, very slow to respond to changing conditions on the surface. At least models behaved similarly.
Naturally, the study is neither global nor completely full, but it seems likely that scientists have a real picture.
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