Tuesday 16 December 2014

Two teenaged girls rescued from soft mud at popular English fossil hunting site.

Two teenaged girls were rescues by teams from Kent Fire and Rescue and the Whitstable RNLI after becoming trapped in soft mud at Warden Point on the Isle of Sheppey (off the north coast of Kent in the Thames Estuary) on Saturday 2014. Initial attempts to by the Fire Service to reach the girls from land were hampered by the incoming tide, leading to a crew from the Lifeboat Institution to be called. The girls were reported to be suffering from mild hypothermia when rescued, but otherwise unhurt.

The two girls trapped in soft mud at warden point on 13 December 2014. Whitstable RNLI.

Warden Point is popular with fossil collectors due to the large number of Eocene fossils it produces. The London Clay outcrops directly on the coast here, and as this is a poorly consolidated, soft sediment, it is easily eroded by the action of the sea, revealing large numbers of highly fossiliferous phosphate nodules, noted for the high quality plant macrofossils (particularly Mangrove Plants) and marine invertebrates (particularly articulated Decapod Crustaceans) that they produce. Unfortunately the same sediment makes conditions at the site extremely treacherous, as the clay readily absorbs large volumes of water, turning into a highly sticky mud that an trap the unwary, as the weight of a human footfall is sufficient to squeeze the water out of the mud beneath the foot, creating a vacuum that prevents the foot from being lifted again.

An articulated Eocene Lobster, Hoploparia sp., from a phosphate nodule collected at Warden Point on the Isle of Sheppey. Discovering Fossils.

Weather conditions across much of the UK have been extremely wet for the past few days, driven by a storm system the popular press have dubbed the ‘Weather Bomb’, driven by warm weather over the Atlantic Ocean, which has brought with it an area of very low pressure, leading to a storm surge that has brought high tides to coastal areas, and very high rainfall levels. The low pressure above oceanic storms causes water to rise there by ~1 cm for every millibar drop in pressure, leading to a storm surge that can overwhelm low-lying coastal areas, while at the same time the heat leads to high levels of evaporation from the sea - and subsequently high levels of rainfall.

The two girls trapped in soft mud at warden point on 13 December 2014. Whitstable RNLI.

his can cause additional flooding on land, as well as landslides, which are are a common problem after severe weather events, as excess pore water pressure can overcome cohesion in soil and sediments, allowing them to flow like liquids. Approximately 90% of all landslides are caused by heavy rainfall. The extent to which this has happened at Warden Point this weekend is unclear, but photographs from the Whitstable RNLI appear to show signs of recent slumping, and the mud produced by recent slumps is particularly dangerous.

Satellite image showing the typical extent of slumping on the foreshore at Warden Point. Google Maps.

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