Monthly Archives: March 2016

The Geology of our Kitchen Bench

gabbro

We have installed a new kitchen bench.  The company that imports and installs this kind of thing refers to the stone as ‘Granite’, a term that is used for pretty well anything that is igneous, crystalline and not marble. Continue reading

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Sea-Level Change; Busting a Few Myths

So you think sea level is the same everywhere!

Canon Fiord, Arctic Canada

Canon Fiord, Arctic Canada

Climate change predicts that sea levels will rise at an increasingly rapid rate.  Some of NASA’s new satellite altimetry data hints that this is already happening.    There is a multitude of voices crying out for government planners to prepare for inundation of vulnerable coasts.  Small island states are particularly at risk.  Forward planning would certainly be a wise move.  If average sea level rises say a metre in the next 100-200 years many coasts will be inundated and storm surges will push farther inland.  Forward planning does make sense. Continue reading

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When Time Goes Missing

How Geologists Interpret Ancient Environments. 6 The value of missing time

When you next look at sedimentary strata exposed in a hillside, cliff or road-cut, don’t just think of it as a pile of rock but as an expression of time; the length of time it took to deposit all that sediment.  Tsatia successionThe mountain exposure in the accompanying image is a great example.  Here, thousands of sedimentary layers, or strata accumulated one at a time, one upon the other.  Geologists tend to think of a succession like this as representing relatively continuous deposition of sediment, not necessarily uniform, but certainly continuous.  However, we also recognize that between each stratum there is probably some missing time that represents the amount of time taken to change from one set of environmental conditions to another.  For example, one layer may have been deposited as beach sand and the overlying layer in an estuary or tidal channel.  The length of time that is missing may be minutes, weeks, 100s or even 1000s of years that, from a geological perspective are like the blink of an eye. Continue reading

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The Ancient Earth 7. The Art of the Stromatolite

Algae, Fossil Slime and Organic Precambrian Art

Stromatolites are the earliest physical life forms on earth; they were the precursors to pretty well everything you see living today. There may be indications of earlier life forms preserved as chemical signatures, but as fossils go, something you can see and touch, stromatolites are it. The oldest stromatolites known are from Western Australia – about 3400 million years old. These ancient structures were built by primitive algae and bacteria, aka cyanobacteria, sometimes referred to as blue-green algae. Clearly life had already evolved to something quite complex by 3400 million years ago.

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