Rock-solid archives record variations in the Earth's orbit

phys.org | 6/4/2018 | Staff
darktm22darktm22 (Posted by) Level 4
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The shape of Earth's orbit around the sun and the orientation of its axis undergo regular variations over periods of thousands to millions of years. These variations—known as Milankovitch cycles after the Serbian geophysicist Milutin Milankovitch—affect the amount of sunlight reaching the planet's surface.

Milankovitch cycles are one of the main drivers of our climate. We know quite a lot about these variations at the present day because we can precisely measure them. Evidence for climate changes due to changes in the Earth's orbit is present in the geological record over the past few hundred million years. The evidence appears as variations in the thickness and composition of sedimentary layers of rock.

Anything - Climate - Changes - Time - Mind

However, hardly anything is known about these climate changes further back in time, bearing in mind that the Earth is 4.5 billion years old. We have not previously been able to learn much about how these Milankovitch cycles have varied throughout earth's history—until now.

We are part of a small international team of researchers from Utrecht University, University of Geneva and Université du Québec à Montréal that conduct careful examination of rhythmic layering patterns in rocks. We then combine these with precise age determinations to calculate the rate that the sediments are deposited. This enables us to uncover the climate secrets of the Earth billions of years ago.

Location - Types - Sediment - Time - Function

In one location, the types of sediment deposited at a certain time vary as a function of the climate. Scientists have studied these variations in the sedimentary record in detail, enabling climate changes in the past to be identified precisely. Typically, the method used to study these variations is spectral analysis, where statistical tools determine if there are cyclic variations in the rock layers.

A simple thought experiment can be useful to understand how changes in the climate can affect the rock record.

Example

For example, if...
(Excerpt) Read more at: phys.org
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