HOW ICE AGES SHAPED PLEASLEY VALE

 

 

Not the deep vale we know today but this would be a few million years ago when ice age melt waters were still carving out the Meden Valley.

Many glacial periods have occurred during the last few million years, initially at 40,000-year frequency but more recently at 100,000-year frequencies. These are the best studied. There have been four major ice ages in the further past.

The period between 130,000 - 110,000 years BC is known as the Eemian interglacial when the climate was similar than it is today. The Vale would have been home to many animals but man would still be some way off to this area.

The climate then slipped back into ice age conditions very quickly, according to sediment records, possibly as little as 400 years and not the usual thousands. Northern forest zones retreated as the summers and winters grew colder. Large ice sheets began to grow in the northern latitudes when the snow that fell in winter failed to melt, and instead piled up from one year to the next until it reached thousands of metres in thickness. As the cold grew more severe, the Earth's climate also became drier because the global 'weather machine' that evaporates water from the oceans and drops it on the land operates less effectively at colder temperatures and when the polar sea ice is extensive.

Even in areas that were not directly affected by the ice sheets, aridity began to cause forests to die and to give way to dry grassland, which requires less water to survive.Eventually, much of the grassland retreated to give way to deserts and semi-deserts, as global conditions reached a cold, dry low point around 70,000 years ago (this is called the Lower Pleniglacial). By this time, most of northern Europe and Canada were covered by thick ice sheets.
By around 60,000-55,000 years ago, conditions around the world had become warmer, though still generally colder than today. The ice melted back partially, and there followed a long 'middling' phase in which the climate oscillated between warmer and colder conditions.

 

30,000 years ago, the Earth's climate system entered another big freeze-up; temperatures fell, deserts expanded and ice sheets spread across the northern latitudes much as they had done 70,000 years ago. This cold and arid phase which reached its most extreme point sometime around 21,000-17,000 years ago is known as the Late Glacial Cold Stage. The point at which the global ice extent was at its greatest, about 21,000 years ago is known as the Last Glacial Maximum. The Last Glacial Maximum was much more arid than present almost everywhere, with desert and semi-desert occupying huge areas of the continents.
Around 14,000 years ago there was a rapid global warming and moistening of climates, perhaps occurring within the space of only a few years or decades. Conditions in many mid-latitude areas appear to have been about as warm as they are today, forests began to spread back, and the ice sheets began to retreat. However, after a few thousand years of recovery, the Earth was suddenly plunged back into a new and very short-lived ice age known as the Younger Dryas. It destroyed the returning forests in the north and led to a brief resurgence of the ice sheets After about 1,300 years of cold and aridity, the Younger Dryas seems to have ended in the space of only a few decades (various estimates from Greenland ice core climate indicators range from 20 - 70 years for this sudden transition) when conditions became as warm as they are today. Around half of the warming seems to have occurred in the space of a single span of 15 years, according to the latest detailed analyses of the Greenland ice core record.



The melt waters have shaped the Vale.
The start of the present warm phase, the Holocene. Following the sudden ending of the Younger Dryas, about 11,500 years ago forests quickly regained the ground that they had lost to cold and aridity. Ice sheets again began melting, though because of their size they took two thousand years to disappear completely. The Earth entered several thousand years of conditions warmer and moister than today; the Saharan and Arabian deserts almost completely disappeared under a vegetation cover, and in the northern latitudes forests grew slightly closer to the poles than they do at present. This phase, known as the 'Holocene optimum' occurred between about 9,000 and 5,000 years ago. Neolithic hunters from their homes in the caves at Creswell, further down the river, would have hunted in the area.
5,000 years ago, there was a further cooling and drying in many areas and conditions became more similar to the present-day. A particularly widespread cool event associated with relatively wet conditions seems to have occurred in many parts of the world around 2600 years ago. The cooling seems to have been relatively abrupt, lasting several centuries before an apparently rapid switch back to warmer conditions. The last cool period was 1400 years ago.

Neanderthal Man in the Meden Valley

Pleasley Vale is claimed to be the birthplace of fossil studies (Palaeontology). In 1862, the Pleasley Mills manager, William Hollins, decided to extend Pleasley Vale House. While doing so the development unearthed a substantial rock cave. The cave, although unsuitable for human habitation contained animal bones of horses, reindeer & cattle and at least 4 wolves now stored at the Wollaton Hall Natural History Museum. It is recorded that most of the bones were kept in Hollins' private collection and are said to contain mammmoth, elephant, rhinoceros & bison.

Four miles north of Pleasley Vale along the Meden Valley are the famous Cresswell Crags where cave drawings of animals have been discovered, which have been dated to around 13000 BC. In addition, Neanderthal Man's stone age tools dated between 60,000 - 30,000BC have been found in the cave system there. 43,000 year old reindeer bones showing cuts made by sharp chopping tools have also been found in the caves. Cresswell Crags is known as one of the most northern regions occupied by man in this period. From around 70,000 years ago the northerly hemisphere was emerging from an ice age which would return 30,000 years later. Therefore, it would seem highly likely that between 60,000-30,000BC the Meden Valley was busy with animals grazing on the flood plains supplying plentiful food for the Neanderthal families living at Cresswell Craggs. The next sustained warm period was around 10,000 years ago, bringing the Neolithic Period and the dawn of modern man and the first agricultural farmers.

 

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