Thursday, 28 June 2018

GOTLAND: SWEDISH TERRENEUVIAN

Gotland: Swedish Island in the Baltic Sea
Gotland, a large Swedish island in the Baltic Sea is a rich source of Cambrian brachiopod fossils and home of the Mästermyr chest, an ancient tool chest from the Viking Age (793–1066 AD) a time when Scandinavian Norsemen explored Europe by sea for trade, raids, colonization, and conquest, not unlike their sea dwelling brethren.

Brachiopods are one of the few groups of marine animals that have a relatively complete extant to fossil record from their sporadic modern distribution all the way back to the Terreneuvian in the early Cambrian.

Thursday, 14 June 2018

TERRACOTTA WARRIORS

The Terracotta Army is a collection of more than 7,000 life-size figures depicting the armies of Qin Shi Huang, First Emperor of China, set in military formation found in an archaeological excavation near Xi'An, Shaanxi Province, China.

Sunday, 10 June 2018

Sunday, 3 June 2018

CaCO3 + CO2 + H2O → Ca (HCO3)2

 
Those of you who live near the sea understand the compulsion to collect shells. They add a little something to our homes and gardens.

With a strong love of natural objects, my own home boasts several stunning abalone shells conscripted into service as both spice dish and soap dish.

As well as beautiful debris, shells also played an embalming role as they collect in shell middens from coastal communities. Having food “packaging” accumulate in vast heaps around towns and villages is hardly a modern phenomenon.

Many First Nations sites were inhabited continually for centuries. The discarded shells and scraps of bone from their food formed enormous mounds, called middens. Left over time, these unwanted dinner scraps transform through a quiet process of preservation.

Time and pressure leach the calcium carbonate, CaCO3, from the surrounding marine shells and help “embalm” bone and antler artifacts that would otherwise decay. Useful this, as antler makes for a fine sewing tool when worked into a needle. Much of what we know around the modification of natural objects into tools comes from this preservation.

Calcium carbonate is a chemical compound that shares the typical properties of other carbonates. CaCO3 is common in rocks and shells and is a useful antacid for those of you with touchy stomachs. In prepping fossil specimens embedded in limestone, it is useful to know that it reacts with stronger acids, releasing carbon dioxide: CaCO3(s) + 2HCl(aq) → CaCl2(aq) + CO2(g) + H2O(l)

For those of you wildly interested in the properties of CaCO3, may also find it interesting to note that calcium carbonate also releases carbon dioxide on when heated to greater than 840°C, to form calcium oxide or quicklime, reaction enthalpy 178 kJ / mole: CaCO3 → CaO + CO2.

Calcium carbonate reacts with water saturated with carbon dioxide to form the soluble calcium bicarbonate. Bone already contains calcium carbonate, as well as calcium phosphate, Ca2, but it is also made of protein, cells and living tissue.

Decaying bone acts as a sort of natural sponge that wicks in the calcium carbonate displaced from the shells. As protein decays inside the bone, it is replaced by the incoming calcium carbonate, making makes the bone harder and more durable.

The shells, beautiful in their own right, make the surrounding soil more alkaline, helping to preserve the bone and turning the dinner scraps into exquisite scientific specimens for future generations.