A geotrail guide giving more information about the Cleveland Dyke at Cliff Rigg Quarry, Great Ayton, North Yorkshire can be downloaded on the following website:
http://tvrigs.org.uk/wp-content/uploads/2008/03/cliff-rigg-final.pdf
(You will need adobe acrobat reader which you can download HERE).

This period began with another major lowering of sea-level together with uplift, and nearly all of Britain, apart from the south-east emerged as land. Because of this, it is most likely that no Tertiary sediments were deposited in Northern England, although thick sequences are known offshore beneath the North sea.
The western side of the British Isles was affected by the opening of the North Atlantic since, by the early  Tertiary, the spreading North Atlantic ridge had developed far enough north to begin splitting Northern Europe from Greenland. Separation  of Greenland  from Western Scotland and Ireland  was preceded by igneous activity, viz. volcanic eruptions and the intrusion of dykes, e.g. in Skye, Mull, Staffa (Fingal's Cave) and Northern Ireland (the Giant's Causeway).

Uplift and the development of the constructive plate margin on the western side of the British Isles were responsible for the general tilting of Britain towards the south-east as well as the renewed activation of major faults, e.g. those surrounding the Alston Block.
 The rising western and northern areas of Britain consequently underwent a great deal of erosion thus exposing much older rocks below, while progressively younger rocks crop out as one travels south-east. It is believed that it was Tertiary earth movements which raised the Lake District area into a dome from which thousands of metres of rocks were eroded away to reveal the underlying Palaeozoic rocks.

It was during this period of separation resulting in crustal tension that a number of linear igneous rocks known as dykes, e.g. the Cleveland, Tynemouth and Acklington  Dykes composed of a type of basalt, were intruded. These are the only tertiary rocks to be seen in Northern England. The Cleveland Dyke and the sites where it was quarried for roadstone can be seen in several places, e.g. at Great Ayton, and at Castleton. In fact, from the the vantage point of Roseberry Topping the dyke, being a more resistant rock, can be seen to form a distinct ridge running in a WNW-ESE direction.

A general trend in global cooling began during the Tertiary, and this was to culminate in the sequence of cold and temperate climates which have affected Britain in the last 2 million years.

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