Among the planets in the Solar System, Earth is unique for having plate tectonics. Mapping our planet through its long history creates a beautiful continental dance — mesmerizing in itself and a work of natural art. This is the first time Earth’s geological record has been used to look so far back in time in an attempt to map the planet over the last 40% of its history. The work, led by Xianzhi Cao from the Ocean University in China, is now published in the open-access journal Geoscience Frontiers.
Our planets rocky surface is split into fragments (plates) that grind into each other and create mountains, or split away and form chasms that are then filled with oceans. There are 4.6 billion years of plate motion to investigate, and the rocks we walk over contain the evidence for how Earth has changed over this time. This is a first attempt at mapping the last 1.8 billion years of Earth’s history – a leap forward in the scientific grand challenge to map our world. Modelling our planet’s past is essential if we’re to understand how nutrients became available to power evolution.
Apart from causing earthquakes and volcanoes, plate tectonics also pushes up rocks from the deep earth into the heights of mountain ranges. This way, elements which were far underground can erode from the rocks and end up washing into rivers and oceans. From there, living things can make use of these elements. A number of critical metals – like copper and cobalt – are more soluble in oxygen-rich water. In certain conditions, these metals are then precipitated out of the solution: in short, they form ore deposits. Many metals form in the roots of volcanoes that occur along plate margins. By reconstructing where ancient plate boundaries lay through time, we can better understand the tectonic geography of the world and assist mineral explorers in finding ancient metal-rich rocks now buried under much younger mountains.
Such a model will allow us to test hypotheses about Earth’s past. For example, why Earth’s climate has gone through extreme “Snowball Earth” fluctuations, or why oxygen built up in the atmosphere when it did. Indeed, it will allow us to much better understand the feedback between the deep planet and the surface systems of Earth that support life as we know it.
Excerpted from a Science Alert article by Alan Collins, Professor of Geology, University of Adelaide