Wednesday, 30 December 2009

Webmaps, history, climate and geology

Chatting with local history buffs brought up amazing facts about climate change and sea level rise since the Middle Ages in East Anglia. One book's sketch map relates how the North Sea coastline differed from today, and how that affected Anglo-Saxon socio-economics there before and after the Norman conquest and the Domesday book.

(click on image for book link, highlight mine)

Firetree has a great tool depicting the sea level rise in the event of global warming and glacial meltdown. See how the 7 m. sea level rise creates a hightstand in East Anglia: It coincides with a necklace of villages along that modelled coastline, and atop modelled islands; the highlighted village of Reach was in fact a port in Roman times.

(click on image for map link, highlight mine)

This is evidently a simplistic analog to pre-mediaval coastline, considering glacial rebound, marshlands etc. depicted in the book above. But it bears a striking resemblance to said sketch map above. This indicated not only a cyclicity in climatic events in the past, but also may give hints to the future, if water levels are allowed to re-occupy similar geographies. And we have abundant documentation compared to many parts of the world, where similar events have had and may yet occur.

Even more fascinating is that gentleman described how sediments from ancient riverbeds remained as highstands after the fens were drained since the Middle Ages. Roads were built on top as well as villages or farms. A very broad image of that is seen on the British Geological Survey webmap below: arrows show where superfical tills parallel main roads, which originated as Roman roads.

(click on image for link, pan/zoom N of Cambridge)