"Flood, Fire and Ferment in North Wales"

Many years ago, I was talking on creation and the Flood to a group of young people training to become better equipped to work in their various churches. I used a picture of folding in layers of sedimentary rock and argued that here was evidence for recent, rapid deposition during the flood. Lack of faulting and other deformations of the rock were suggested to show that the rock was soft when it had been folded. After the session, a geology graduate came up to me and assured me that there was lots of deformation of the rock layers at the site - how did he know? He had been there! I had merely purchased a slide to illustrate my point. I had not been there! The usefulness of the morning was only saved by the discretion of the geologist. Had he made the comment publicly, the whole audience would have been quite justified in dismissing all that I had said in the sessions as unreliable. I have not yet visited the fold - maybe next year....

In July, there was an opportunity to look at some rock formations in North Wales, on a field trip run by Michael Garton and David Tyler. There were a number of questions to ask so that we could better understand the history of the earth since creation.

• What were the conditions like when these rocks were formed?
• Can we tell if they were all laid down at the same time or in a succession?
• How do these rocks fit in to the record of a global flood of Noahís time?

We started the day on the beach at Llandudno looking at the layers of limestone that form the Great Orme and Little Orme and ended at the foot of Tryfan, one of the Welsh mountains. At Llyn Padarn, our first outcrop, we looked at the tuff deposits. This rock was formed as a hot fast-moving ash, that became welded together as it cooled, producing a vast thickness of rock - up to 2,000m in places and without any breaks. This could represent 7 hours of constant ash flow from a large volcano in the area - something that we do not see anywhere in the world today. Clearly, this was at an extraordinarily catastrophic event.

A short journey up the valley and we were able to look back at the area of tuff. However, we were then standing on a quite different rock - a conglomerate. This is a sedimentary rock, this one looked like something akin to concrete; a fine-grained background rock with stones of various sizes and shapes embedded in it. The conglomerate here contained some pebbles of a green rock known on Anglesey as well as lumps of the grey tuff we had seen earlier that morning. The irregular shapes of the rock pieces showed us that they had been eroded recently, without time for them to be ground down into sand, or even small round pebbles. The size of pieces, some 2-3 cm diameter, meant that it was no gentle stream that carried them down - it must have been a fast-flowing, turbulent body of water to keep pieces of this size moving along. The rocks of Anglesey and the tuff seen earlier were already part of the landscape when erosion took away boulders and stones and deposited them later to form the conglomerate. Erosion of earlier rocks was providing the materials for the next rock layer.

Looking up the slope of the hillside, with our backs to Anglesey, there were a few areas of exposed rock were we could see the conglomerate merge into sandstone. A short walk uphill and there was an abrupt change in the rock, to slates. These rocks can be split readily into thin layers to form the typical roofing slate. Originally soft muds, they were then squashed between two masses of rock; the tuffs and sandstones that we had already seen and another mass higher up the valley. The rock beds are no longer horizontal, but folded and at times lying almost vertical, such as at the Idwall slabs in the Devilís Kitchen much loved by rock climbers.

Another short drive up the valley and we came to another bed of tuff seen as large buttresses on the valley sides. Near here we saw a type of fossilised raindrop - large raindrops that had gathered a covering of ash as they fell through the volcanic dust clouds. We learnt that they were thought to have fallen into shallow, still water or they would have been broken up before they could be turned to stone.

Higher up the valley are layers of sandstones deposited in shallow water. The grains of sand were formed by erosion of volcanic ash and then pushed up by later earth movements. In these sandstones were shells (brachiopods) similar to cockle shells. These animals live in shallow water, but here they were lying as accumulations of single half shells upside down. There was no evidence of any shells attached to a sea floor, so we can be sure that they did not grow in this position, but were washed in from elsewhere.

The last task of the day was to estimate how long it might have taken to form the mountain of Tryfan out of beds of volcanic ash and sandstone. Rates of deposition observed today were for the calculations. The mountain is about 1,000m high and formed of a number of clearly distinguishable bands of rock that are now sloping down from SE to NW. There are three ash flows of 35m, 30m and 25m each and a 250m deposit of sandstone between two ash layers. On close examination the sandstone could be seen to be of a number of cross-bedded layers. This means that it was originally laid down rather like a band of sand dunes moving across the landscape - sideways. There are several beds of sandstone in the deposit, the boundaries between the beds were pauses between the layers being laid down, but as there is no evidence of erosion between the beds, it can be assumed that these pauses must have been quite short. An addition, there is a narrow (5m) layer of siltstone. A thick layer of igneous rock was pushed in between the siltstone and top ash layer but this was not included in the calculations because it occurred later.

Ash flows - at more than 100m/hr        35m                      5 minutes
                                                              30m                    4-5 minutes
                                                              25m                    2-3 minutes
Sandstone- at rates of /m                    250m             18 hours - 1 week
Siltstone- a few minutes / m                 5m                         1 hour

Total                                                   345m            18+ hours - 1 week

This is very rapid compared with conventional geology, but comparable with rates in the recent small scale eruption of Mount St Helens.

What were the "take-home messages"?

• Firstly, the sheer magnitude of events. Standing in front of a small cliff face formed out of tuff, I was sure that I had no chance of survival if that had been approaching me at over 100 metres/h.
• Secondly, the clear evidence of time in the rock layers. The green rocks on Anglesey and the tuff of Padarn must have been formed first for broken up pieces to be carried away and deposited as the coarse fragments in the conglomerate.
• Thirdly, how can we relate this to the flood?
• The thick layers of tuff certainly tell a story of catastrophic volcanic eruption, especially the lowest layer.
• The conglomerate clearly tells of rapid, erosion and deposition.
• The slate tells of strong earth movement, squashing and deforming previous mud-like sediments.
• The raindrops and sandstones higher up the valley of Llyn Padarn tell of shallow water deposits. Were these formed in shallow water in the middle of the flood, or towards the end? My own feeling is that I do not think I would like to draw conclusions from this one site; better to visit many sites in the UK and maybe some abroad first.

It was well worth a day to look at the rocks for myself in the company of trained geologists; a small number of such trips would provide some good first-hand evidence to back up discussion points on the Flood for future lectures. My thanks to all those who contributed to making the day possible, especially to those who led the discussion. Put some boots, a camera and a waterproof in the car and see you next time!

Nancy Darrall (December 1998)

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