Saturday, March 14, 2009
Daily growth increments
I've set myself a little daily practice of drawing a fossil every day. I draw them from pictures in books, as I don't have a fossil collection of my own. I do own one fossil field guide and I found a couple of well illustrated tomes in the library.
As always with drawing, a few hours of practice improves my skills and after only a week I'm starting to be quite pleased with these efforts, imperfect as they are. I'm not attempting to be scientifically accurate, which is lucky as there's nothing scientifically accurate about my attempts. Rather I'm thinking about working them with thread, or as paper cuts. Not sure yet. Maybe drawing them will be enough.
Copying pictures from books has the advantage of allowing me to actually read bits of text that I might not be motivated to otherwise peruse. Interesting snippets included finding out about 'zone fossils' which are from certain hard bodied animals which existed for a short period of time but spread widely across the planet. Their presence in geological strata is a flag indicating the era of the strata. Trilobites are one of the zone fossils for the Paleozoic era. Here's a somewhat misshapen Trinucleus trilobite from the Ordovician strata.
Given my on-going obsession with coral, I was interested to read that corals work as fossil clocks. Modern corals show bands of around 360 growth increments each year but corals such as Ketophyllum from the Silurian era shows growth increments in annual groups of 400. This suggests that 440 million years ago there were more days in the year and that each day was shorter. Astronomy shows the Earth's movement around the Sun has changed by almost exactly the amount that the fossil corals show.
Which I take as further reinforcement of the amazing power of coral to communicate useful information in languages that I am attempting to record with needle and thread. My big current project, The Sixth Extinction, is coming along nicely.