A puzzle from the past

If we take part in a road trip (while we miss this at the moment), do not fall asleep. See the rhythms of nature. Every single rock has a story.

A virtual tour: chalk cliffs vs. basalt columns

South England’s coastline features chalk cliffs. Chalk is made of skeletons of coccoliths. They sank down on the seafloor from the sunlit waters above. The 100 meters cliff shows a 100 million years history – peaceful deposition during the Cretaceous followed by dramatic movement of land and sea.

While hiking in Lake District, views are different. Mountains consist of igneous rocks that are no longer white. As a result, we may find the drinking water not that ‘hard’. As we move on, stop by a giant rock, and stare at the scratches, a picture of glacier just appears.

Further north of the land, we may be impressed by the dark basalts. They are formed from cooling of lava, related to Cenozoic volcanic activities when the opening of the Atlantic began.

Geochemists are using elemental and isotopic tools to decode the clues about the Earth’s history. For example, the rise in atmosphere oxygen level will mobilise redox-sensitive elements (like iron and chromium), and will change their isotopic compositions. The delicate variations in metal isotope signatures that are recovered from sedimentary rocks are hints of the past climate change.

An example showing the use of metal isotope signature to decode the Earth’s evolution: anomalously high chromium (Cr) isotope values recovered from ancient sedimentary rocks may indicate rise of oxygen and therefore possible commencement of biology. Figure from  Planavsky et al. (2014) ‘Low Mid-Proterozoic atmospheric oxygen levels and the delayed rise of animals’ Science.

The power of nature not only travels in time, but also shapes nowadays landscapes. I thought of a field trip to a small island off the coast, which is characterised by muddy flat on its west coast while sandy beach on its east. Under weak hydrodynamic condition, fine sediments deposit, and form the salt marsh. On the other side, contrastively, strong currents bring the coarse sands, as well as tourism.

When human activity adds onto the natural power, things become more complicated. Once during my master’s project, I surveyed an estuarine area where metal rich effluents were discharged from industries. You know, however, estuary is the sensitive zone that links land and sea and hosts living communities. Hopefully I can see the area is now healing from lack of mitigation,

‘Things will settle back to their original rhythms, season after season’.

We’re now stepping into Anthropocene, a proposed geological epoch dating from the commencement of significant human impact on Earth’s geology and ecosystems. This is an epoch that our actions can positively shape the future of our blue planet.

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