page_title: Geology of Yorkshire
section_title: The North York Moors
hierarchical_section_title: Geology of Yorkshire / Topography / The North York Moors
caption_attribution_description: English: Boulby Cliff. Looking east from near the top of Boulby Cliff - the highest point on the east coast of England.
context_page_description: The Geology of Yorkshire in northern England shows a very close relationship between the major topographical areas and the geological period in which their rocks were formed. The rocks of the Pennine chain of hills in the west are of Carboniferous origin whilst those of the central vale are Permo-Triassic. The North York Moors in the north-east of the county are Jurassic in age while the Yorkshire Wolds to the south east are Cretaceous chalk uplands. The plain of Holderness and the Humberhead levels both owe their present form to the Quaternary ice ages.
  The strata become gradually younger from west to east.
  Much of Yorkshire presents heavily glaciated scenery as few places escaped the direct or indirect impact of the great ice sheets as they first advanced and then retreated during the last ice age.
context_section_description: The geology of the North York Moors is dominated by rocks of the Jurassic period. They were mostly laid down in tropical seas 205 to 142 million years ago. Fluctuations in sea level produced different rock types varying from shales to sandstones and limestones derived from coral. These marine and delta deposited rocks are superbly exposed on the Yorkshire coast from Staithes to Filey.
  Subsequently, about 30 million years ago, the land was uplifted and tilted towards the south by earth movements. The upper layers of rock were eroded away and the older rocks were exposed in places. Because of the tilt the oldest rocks became exposed in the north. These are the bands of shales and ironstones on the northern scarp of the moors and Cleveland Hills. The middle layers form the sandstones of the high moors and the youngest layers of limestone form the tabular hills. In the dales where the rivers have cut through the younger rocks there are also exposures of older shales, ironstone and sandstone. Rosedale is an example of this.
  During the Quaternary period, the last 2 million years, the area has experienced a sequence of glaciations. The most recent glaciation, the Devensian, ended about 10,000 years ago. The higher parts of the North York Moors were not covered by the ice sheets but glaciers flowed southwards on either side of the higher land mass.
  As the climate became warmer at the end of the ice age the snowfields on the moors began to melt. The meltwater was unable to escape northwards, westwards or eastwards because it was blocked by ice. Huge torrents of water were forced southwards. Water from the Esk valley area flowed southwards gouging out the deep Newtondale valley as it went. Water from the moors formed a vast lake in the area of the Vale of Pickering. Eventually this lake filled its basin and then overflowed at the lowest point which was at Kirkham. Here it cut the steep sided Kirkham gorge. When the glacier finally retreated they left deep deposits of boulder clay and glacial alluvium behind. The boulder clay blocked the eastern end of the Vale of Pickering causing a permanent deviation in the course of the River Derwent. Alluvium from the glaciers covers many areas to the north of the moors and in the Esk valley
caption: The Jurassic strata of Boulby Cliff
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