Did the Earth Move For You?
Geohazards in Eastern Yorkshire
Mike Horne FGS
Summary of Lecture -
In the past people may have looked towards religion and priests to explain unknown phenomena.
Now they look toward science.
When a 'natural disaster' occurs the press and media look for a scientific expert!
Any expert to provide suitable quotations.
But this does give scientists the opportunity to tell the public about science!
Earthquake on Wednesday 27th February 2008; epicentre near Market Rasen about 30 miles from Hull; at 12-50 am; 5.2 on the Richter scale. Plate tectonics explains how earthquakes are generated when plates collide or are subducted. But the UK is not on a plate boundary!
Flooding on 25th June 2007 in Hull and parts of the East Riding of Yorkshire; my office at the University was flooded to a depth of 6 foot and virtually everything there was damaged beyond recovery.
Landslips at Holbeck Hall Scarborough on 7th June 1993; Knipe Point Cayton Bay on 4th April 2008; and Aldbrorough any day of the week.
Can an understanding of Geology provide some of the reasons for these disasters? Could geologists advise planners about risk assessment for the future?
The Geology of the East Riding is dominated by the Chalk Wolds - a major aquifer. The whole of Holderness consists of unconsolidated Boulder Clay deposited by glaciers at the end of the last 'ice age' about 12 000 years ago. Beneath the Chalk are other clays, such as the Speeton Clay and Oxford Clay.
Clays can absorb water and swell when they do. They become plastic when wet. Water will not run through them. Once they are saturated water will run off. When they dry out they shrink.
Facts about Hull and Holderness -
In Holderness "rockhead" (the top of solid rock surface) is below sea level, doe example it is about -12m OD at the University.
The unconsolidate deposits above rockhead are up to 80 metres thick.
Peat, clays and boulder clays shrink in periods of drought and can cause localised subsidence.
The area is low lying and at risk of flooding
Parts are prone to flooding from escaping groundwater
There are soluble salt and potash deposits at depth in the area.
The removal of coal by deep long-wall mining to the west will cause subsidence
Sand and gravel deposits are being quarried in the area
Coastal erosion in Holderness is between 1.5 and 2 metres per year.
Coastal defences can halt and accelerate the coastal erosion [groynes trap the beach material that usually moves by long shore drift protecting the base of the cliff from breaking waves; but this deprives the beach to the south of material thus increasing the rate of erosion.
Global sea level rise is about 1 cm per year.
Isostatic re-adjustment after the melting of the glaciers means that the land in Scotland is slowly rising and it is sinking in southern England.
Low pressure, north-easterly storms and spring tides can cause tidal surges in the North Sea.
Urbanisation - compaction of the soil and ground, more roads, paved gardens, decking and removal of trees will cause more run off during heavy rain.
The area has been affected by earthquakes in the past.
This is what East Yorkshire will look like in 500 years time
if we do not plan to protect it!
Sources and credits -
Hull Daily Mail 27/02/2008
West Hull Advertiser 28/02/2008
British Geological Survey Website.
BBC Humber website
Photographs of flooding by Paul Crisp
The Telegraph website.
Photos by Mike Horne
Geology of East Yorkshire map by Nikki Abramson for a Display at the Treasure House in Beverley.
Jason I (ed) 2004. Britain beneath our feet. British Geological Survey Occasional Publication number 4. Keyworth. 114pp. isbn 055272470-9
S C Porter, J Park, B J Skinner 2003 The Dynamic Earth: An Introduction to Physical Geology. 648 pp and CDROM; John Wiley and Sons [and associated website]