North York Moors Geology 

 Geology in the North Yorkshire Moors National Park!


North Yorkshire has an interesting and changeable geographic history. Generally the geology of North Yorkshire comprises of sedimentary rocks which slope gently to the east leaving the oldest rocks present in the west of the County and the youngest in the east.

The North York Moors dominate North-east Yorkshire where the Hambleton Hills and North Yorkshire Moors rise abruptly out of the earth to the east of Thirsk. This whole area mainly comprises of mudstone and sandstones of Jurassic age. The porous sandstones give rise to the free-draining soils that support the heathland vegetation of the North Yorkshire Moors. These marine and delta deposited rocks are superbly exposed on the Yorkshire coast from Staithes to Filey and you can find many fantastic fossils falling out the rock face.


Lower Jurassic Shales, clays and thin limestones and sandstones were deposited in a shallow sea at the beginning of the Jurassic era.

Middle Jurassic during this time the moors experience a period of gradual uplift resulting in mudstone and sandstone being deposited on a low lying coastal plain crossed by large rivers.

Upper Jurassic at the end of the Jurassic era the land once again began to sink beneath the sea. At first the sea was shallow and calcareous sandstones and limestones were deposited.


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.

 

 

Approximately 20,000 years ago the the most recent glaciation, the Devensian, ended. As the climate warmed up at the end of the ice age the snowfields on the moors began to melt. The resulting meltwater was unable to escape eastwards, westward or northwards because it was blocked by ice. This meant Huge torrents of water were forced south from the Esk valley flowing southwards gouging out the deep Newtondale valley as it went. In the area of the Vale of Pickering water from the moors formed a vast lake. After a while 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.