* Astronomy

Scientists have found that Britain owes its island status to a catastrophic flood that swept away in less than 24 hours the hills that once joined the land mass to France.

The flood, which took place between 400,000 and 200,000 years ago, instantly turned Britain from being a peninsula of continental Europe into a separate entity, changing forever the way it would develop.
The finding has emerged from an advanced sonar survey of the sea bed of the English Channel that revealed huge scour marks, deep bowls and piles of rock that could have been created only by a giant torrent of water. If confirmed, it will force an important revision of British prehistory.
It had been thought the Channel had formed by slow erosion combined with rises in sea level that took place over millions of years, rather than by a sudden, biblical-style catastrophe.

"This could have been one of the most powerful flood events ever known on earth. It would have cut through the chalk hills joining Britain to Europe and created a Niagara-style waterfall 300ft (91.5m) to 400ft high" - Chris Stringer, head of human origins at the Natural History Museum in London.

Professor Stringer has been overseeing the Ancient Human Occupation of Britain project, which brought together researchers from a range of disciplines to trace how Britain first became populated. Among the researchers were a team from Imperial College, in London, led by Sanjeev Gupta, who used sonar to survey the sea floor several kilometres off the Sussex coast.
The equipment is able to see through thick layers of sediment to the sea bed lying beneath. The team was surprised to find the remains of a huge valley, partly hidden by accumulated mud, running southwest from the Strait of Dover.

"In places this huge, underwater valley is more than seven miles (11km) wide and 170ft deep, with vertical sides. Its nearest geological parallels are found not on earth but in the monumental flood terrains of the planet Mars. This suggests the valley was created by catastrophic flood-flows following the breaching of the Dover Strait and the sudden release of water from a giant lake to the north" Dr Gupta said in an abstract published at an academic conference.

In the scenario, there was a high chalk ridge linking Britain and France running roughly between Dover and Calais.
Northeast of this ridge the land sloped down until it met the North Sea, which was much smaller then and was bordered by a shoreline that ran from Norfolk to northern Germany.
Several European rivers, including the Rhine, Seine and Thames, ran northwards to this shore, emptying into the sea.
Between 400,000 and 100,000 years ago, northern Europe suffered repeated glaciations. During one of these, an ice cap up to 1.6km thick reached so far south it stretched from Scotland to Denmark, damming the North Sea. This turned it into a freshwater lake that, fed by rivers, deepened over thousands of years.

"The lake would have been hundreds of feet above then sea level. One day it just overflowed the top of the chalk ridge and started pouring over. Once the torrent started it would have ripped through the chalk and poured down towards the Atlantic" - Professor Stringer.

Global sea levels were far lower then than now because so much water was locked up in the ice caps. This meant that Britain was joined to France all the way along its south coast - and the cascading water had to carve its way across the landscape.
The discovery of the Channel flood may help to solve one of the enduring mysteries of British archaeology - the apparent abandonment of the British Isles by humans for 120,000 years.
Researchers have found that humans first arrived in Britain at least 700,000 years ago. They were driven out by repeated glaciations but returned whenever the land warmed up. They vanished completely between 180,000 and 60,000 years ago.

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Eight times humans came to try to live in Britain and on at least seven occasions they failed - beaten back by freezing conditions.

Scientists think they can now write a reasonably comprehensive history of the occupation of these isles.
It stretches from 700,000 years ago and the first known settlers at Pakefield in Suffolk, through to the most recent incomers just 12,000 years or so ago.

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The heatwave has revealed fleeting traces of early settlements to historians taking a bird's eye view of Scotland. The conditions this summer have proved ideal for aerial archaeologists who document the buried sites, which appear in ripening crops or scorched grass. The Royal Commission on the Ancient and Historical Monuments of Scotland said it was one of the best in its 30 years. Discoveries have included various prehistoric settlements.

"Bits of the Borders, some of the Cheviot foothills, parts of Fife and the Moray Plain have produced previously unknown sites. Town Yetholm through to Morebattle have been producing material, which is parched out in grass. We have seen various types of prehistoric settlements usually as circular or rectangular enclosures and burial sites" - Dave Cowley, the aerial survey manager at the RCAHMS.

Archaeological sites become visible most commonly on farmland during the summer months.

"In the lowlands, in particular, ancient sites and monuments have been levelled out by agriculture, and while these sites are not usually detectable, during hot spells they can become visible from the air. When cereal crops are planted on the top of these sites, different rates of growth and ripening can cause buried features to reveal themselves. Crops will often grow taller and greener above ancient ditches because extra water and nutrients are found there, while buried walls or paths can deprive plants of nutrients, showing up as yellow patches, known as parching" - Dave Cowley.

Because of the farming calendar, archaeologists face a race against time to get all the information catalogued.

"We have to conduct all our investigations August, as we have to photograph as many sites as possible once the crops have come up, but before they are harvested. The sites are no longer visible and won't be until the next spell of hot weather" - Dave Cowley.

The RCAHMS aerial survey has undertaken about 1,000 flights, using a four-seater Cessna aircraft from its base in Edinburgh, and it has produced more than 100,000 images of the country since 1976.

"Sites become visible every summer to varying degrees, but for the past few years we have had fairly poor summers. This year, ideal conditions meant that sites became visible of which we had been completely unaware, including a prehistoric settlement near Melrose, and an Iron Age enclosure at Letham. In addition, existing sites have appeared in much greater detail. The information will now have to be analysed thoroughly and will be made available to the public on the Canmore Database. This is what gives future generations access to information and records on every aspect of our built environment. We can only speculate at the moment as to what this year's findings may tell us, but one key thing is that we have discovered more Iron Age locations" - Dave Cowley.

Sources BBC News

The summer drought has unearthed a treasure trove of finds for historians taking a birds eye view of Wales. Heatwave conditions, which have parched the Welsh countryside, proved ideal for aerial archaeologists. They were described as the best for at least decade with a host of buried sites revealed from the air.
The Royal Commission on the Ancient and Historical Monuments of Wales made major discoveries using light aircraft to survey the Welsh landscape.

"It has been absolutely astounding. Discoveries have been made across Wales visible both as cropmarks in ripening crops and scorched grassland" - Royal Commission spokesperson.

They include two early Neolithic causewayed enclosures, built in Wales 6,000 years ago, of which only three were previously known. One was spotted in Radnorshire and the other in the Vale of Glamorgan. Other significant discoveries include a Bronze Age ritual enclosure, near Aberystwyth, and scores of prehistoric hillforts across the entire country.

"Cropmarks first began appearing from the air during June, in Gwynedd, Montgomeryshire, and the Vale of Glamorgan. But into July and August we have seen stunning results from all parts of Wales. As the hot weather has progressed some remarkable sites have been discovered. From the Bronze Age we have scores of round barrows, once used for burial, visible as plough-levelled circles in fields. Sometimes the central grave pits are still visible. At Goginan, near Aberystwyth, a great circular enclosure was discovered with a barrow close by, likely to be a bronze age temple which may once have contained a circle of upright timber posts. Previously unknown hill-forts and prehistoric farms have been found in considerable numbers across the southern Llyn peninsula, Ceredigion, Carmarthenshire and Montgomeryshire, telling us where pre-Roman Iron Age communities lived and farmed.
It has been a hugely successful year for aerial archaeology in Wales and we may not see another like it for a decade. I know I have some months of work ahead of me to work through the discoveries, notifying local archaeologists and ensuring some of the most remarkable are visited on the ground and further studied." - Dr Toby Driver, Project Manager for the Aerial Survey programme at the Royal Commission.

Source: icNorthWales