Mean of the earth

Tim continues teaching the 3D modelling software he uses. Today our source was a bathythemetic map of the world. While showing me various functions he pointed out that the programme had calculated that in approximate terms the mean height / depth - depending on how you view it - of the Earth's surface is 1424 metres below sea level!

A statistic which for a moment held us both rapt, bringing home afresh the extent to which the sea, rather than earth, dominates the surface of the planet.

The most common height above sea level is 85 metres and the least 3,3800 metres below.

turning the world inside out

I have begun to learn the software Tim Le Bas, the scientist with who I am working, uses to model bathymetric data. I start with a map of the world, reversing the usual blue /green coloring of land and sea and going on to reverse height and depth. At one point I transform the Himalayas into a void – even then its hard to conceive of the fact that if Challenger Deep was turned inside out it would tower a mile higher than Everest!

Circling above the globe it is possible to change your viewpoint at will, turning the world upside down in a second, its amazing though how, once the familiar, western centric viewpoint of the Americas, Europe and Africa is displaced, hard it is to orientate at all. Left to my own devices I manage to produce a set of strange exaggerated, psychedelic landscapes, which look like covers for a Yes album. These and other experiments can be seen on the Maps/Models page

Reverse map of the world
Reverse map of the world

Physiographic diagram of the South Atlantic

Went to the British Library Map Room today to view Tharp's Physiographic diagram of the South Atlantic Ocean, the Caribbean Sea, the Scotia Sea, and the eastern margin of the South Pacific Ocean. It is always a thrilling moment when you are handed a carefully packaged document, that may not have been viewed for many years, from the BL’s collections . Even so spreading the map out on the table was a revelation, what emerged, fold by fold, was a richly detailed drawing of the seabed which I spent a good hour pouring over, as much for the sensual and aesthetic experience of doing so, than anything else. The drawings of seamounts, of which an estimated 30,000.00 cover the globe, resemble maps of Tolkein's Middle earth.

I have discovered that a number of Tharp maps are held in different libraries throughout the UK, including the V and A and the Maritime Museum, suggesting the possibility of a Tharp pilgrimage to view all of them. NOCS have one of the North Atlantic, which I shall investigate on my next trip there.

 

Detail - Congo Submarine Canyon and Angollan Abysmal Plane - Tharp, Physiographic Diagram of the South Atlanticc
Detail - Congo Submarine Canyon and Angollan Abysmal Plane - Tharp, Physiographic Diagram of the South Atlanticc

Marie Tharp

At coffee break someone mentions Marie Tharp describing her as an ‘artist who drew sections of the seabed’. Further research uncovers a cartographer and geologist, working in the fifties - a time when women were not allowed onto research vessels, who with a pen, ruler and data collected by her colleague, oceanographer Bruce Heezen, plotted the Mid-Oceanic Ridge, a line of undersea mountains that run along the sea bed between Europe/Africa and the Americas. An undertaking that laid the foundations for theories of plate tectonics and continental drift which were controversial until well into the 1960’s.

‘She wondered whether the depression was evidence of a continuous rift - a crack in the world - down the middle of the ridge. And … in turn whether that rift might be evidence of what scientists now call seafloor spreading, popularly known as continental drift. She and Mr. Heezen argued about it. She threw erasers and bottles of ink at him. It took him some time to come around. “I discounted it as girl talk and didn’t believe it for a year”

Many of the tributes to Tharp, who died in 2006, emphasize her fiery nature and powerful intuition observations which charecterise her achievements in a way that it is hard to imagine happening to a man, the later offering never the less a point of reference for my own less than rational approach.