Sunday, 15 July 2012

living deep time

I visited the Fossil Grove in Victoria Park in Glasgow today for the first time. This is an amazing gem in Glasgow's museums, and one that is so often overlooked. The Fossil Grove consists of the cast remains of the stumps and roots of a group of fossilized trees which were revealed in 1887 during excavations when the park was being created to mark Queen Victoria's golden jubilee. Quarrying for dolerite, the workers quickly realised the sandstone casts were of great scientific significance, and the city ensured the grove was protected by a custom made building, one of the first to protect a geological site of special interest.

The Fossil grove when it was first excavated in 1887, before it was protected by it's building.

Schoolchildren visiting the grove in the 1948

"There are at least 10 erect trunks and root systems exposed of the clubmoss tree Lepidodendron veltheimianum and Stigmaria ficoides (the latter being the roots of the former).  There are also parts of trunks lying across the floor of the quarry.  The trees were submerged in sand and clay as sea level changed.  Rippled sands, similar to those found on the lower reaches of present-day beaches, provides evidence of water currents moving between the trunks depositing sediment.  The trees grew in an equatorial or tropical mangrove swamp similar to the everglades of Florida. 

After the clubmoss trees had died, their soft interiors quickly rotted to leave them hollow.  Their trunks then filled with sand before the sediment around them enclosed them completely.  The organic remains of the trunk became a thin coal separating the sandy interior from the shales and sands surrounding the trunks.  During an episode of volcanic activity, a thin dolerite sill was intruded about 90cm above the floor of the quarry cutting through the trunks.  Some slight earth movements have caused the sediments (and the trunks) to tilt slightly, sloping gently towards the NE, but the slight distortion of the trunks themselves are likely to be due to palaeocurrents rather than tectonism (Gastaldo 1986)."

We arrived early in the day, the first visitors, and, with no-one other than a very helpful guide present, were surprised by the intense, quiet presence of these old petrified remains. I was relieved to see that the video projector wasn't working, and instead benefitted from a display that held a quiet kind of dignity that museums sometimes don't allow it's artifacts these days, pressured as they are to make all things 'accessible'

These special trees had lain quietly for around 330 million years, and the quiet atmosphere of the fossil grove got me thinking about deep time and how, when looking at rock, one readily accepts, even if one fails to fully comprehend, time beyond human understanding. Faced with recognisable objects that were clearly, at one point, huge living organisms, these 'understandings' of deep time became even less robust - or rather, confused - for me.  How can some things so very, very old, things that have witnessed numerous ice ages, that pre-date the dinosaurs, that existed on equatorial land (these are tropical trees which grew when the land that Glasgow sits on was located at the equator) and have journeyed northwards by continental drift bearing witness to the supercontinent of Pangaea's split; how can things this old look, well, commonplace? They don't match my understanding of the  deep time of geology as regularly encountered in rocky mountainous landscapes. The amorphous shifting, sliding, bulging and intrusion of rock formations that can be so clearly seen in Assynt for instance, Scotland's mecca for students of geology, and where the Moine thrust can be clearly viewed from the roadside, is fantastical and mind boggling. But the simple silence of these trees weathering ages and eras, and remaining relatively intact seems to me to be something quite different altogether.

photo: L Punton

Interestingly, our guide informed us that despite finding such large specimens of trees found preserved in situ, the space around them giving us information as to the density of trees that would ordinarily be found in the full extent of this woodland site, no other living specimens were found. No insects, no other plant life, in land that would have been lush with other life-forms. It's still not really known why this should be the case. The day before, I'd read of the Fortingall Yew, a yew tree in Glen Lyon that is believed to be the oldest living organism in Europe. Yew trees can't really be dated like other trees, since the interior wood naturally rots and decays,  eventually leaving a hollow interior  whilst the exterior lives and grows. The decay of the heartwood has created the illusion of more than one tree, but it's measurement in 1769 put it at around 52ft in breadth, and the Fortingall Yew is believed to be somewhere between 5-10 thousand years old. In human terms, even this is a timescale difficult to truly negotiate and place oneself within. But the yew's resistance to dating because of it's hollow core means it doesn't fully yield to measurement, to being quantified. The Lepidodendron trees of the fossil grove have been preserved precisely because of their similarly hollowed interiors, yet they too resist and retain their quiet mystery precisely because they are old way beyond our ken.

The fossil grove as it is today. Photo: L Punton.
The fossil grove when it had a curved platform running through it's length

two views of the same deer