The rest of the Tertiary:

When the last of the Tertiary igneous activity eventually ceased on Mull about 55 MY ago there followed millions of years of  denudational processes which weathered and eroded the igneous rocks. Much of the original extensive lava plateau was gradually removed during this time and many of the intrusive igneous rocks were uncapped. During the last 26 MY, Mull, and the British Isles, gradually acquired the shape recognisable to us today. The North Atlantic was still widening at the rate of approximately 2.5cms a year and this had the effect of stretching and warping the western edge of the European plate. Britain had drifted further north and was now moving eastwards. In mainland Britain, especially in the upland blocks of Scotland, Wales, the Pennines, Lake District and Southwest England there was slow, but repeated uplift. In the North Sea, Irish Sea, parts of the English Channel and on the continental shelf to the west, the crust sagged. This westerly uplift combined with sinking in the North Sea gave the British Isles a gentle tilt eastwards. As any high land area is subject to faster denudation rates than lowland areas it was the rising land in the west which supplied sediment which was then deposited in the surrounding sea areas. Agents of erosion, rivers and the seas wore down the stumps of the Caledonian and Variscan fold mountain chains creating extensive plains which were later upwarped hundreds of meters in the repeated phases of uplift. These  eroded lowlands were then transformed into plateaus or ‘upland plains’ which today still dominate the skyline of much of Britain’s highland regions. As time went on the climate gradually changed from warm to cold. Rivers which had been the main agent of erosion in these emerging highlands were followed by glaciers which cut deep valleys into these once flat topped uplands.