Cretaceous.—Scotland is embraced within the scope of the great Upper Cretaceous marine transgression. The Upper Cre taceous rests indifferently on Lower Lias and later Jurassic rocks. It is known in situ (Skye, Scalpa, Raasay, Eigg, Mull, Morven), as block remanie in a Tertiary vent (Arran), and as remanie flints (Aberdeenshire). The Morven succession is : Cenomanian Green sand (45 ft.); White Sandstone (35 ft.) ; Silicified Chalk with Belemnitella mucronata (5 ft.). This condensation of the suc cession is typical of the Hebrides. The White Sandstone consists of desert sand blown on to the Scottish shore of the Franco Britto-Russian Chalk sea. In Morven, Cretaceous is still pre served 1,600 ft. above sea-level.
Tertiary.—The Cretaceous Chalk was upraised, weathered and silicified and its crannies filled with desert sand (Mull). Subse quent conglomerate and lateritically weathered ash bespeak a change to moist climate and volcanic eruptions. Subaerial basalt lavas characterise Skye, Eigg, Mull. and Morven. Leaf-beds inter calated near their base suggest early Eocene (Ardtun). Excep tionally these lavas are columnar (Staffa). The basalt succession in Mull is: olivine-rich, 3,00o ft.; olivine-poor, 3,00o ft. The Sgur of Eigg pitchstone seems to be an acid lava that flowed down a valley, the sides of which, consisting of basalt, have since been eroded away. Great plutonic centres occur at St. Kilda, Skye, Rum, Mull, Ardnamurchan and Arran. Some think that most of the lavas, still preserved, were fed from these centres. A Kilauean sink, repeatedly renewed in central Mull, was often occupied by a crater-lake, and lavas flowing into it developed pillow-structure. Vent-agglomerates are abundant in Skye, Mull, Ardnamurchan and Arran. In the last named island, the latest surface-rock in situ is Keuper, but masses of Rhaetic, Lias and Chalk have tumbled into a Tertiary vent and thus escaped erosion.
The Skye plutonic centre is well known for its gabbro to granophyre succession; Rum for its peridotites; Mull and Ardna murchan for their ring-dykes—in Mull the plutonic succession is very complex and begins with granophyre, in Ardnamurchan it is essentially gabbroidal ; Arran is specially noteworthy for the doming of its granite's roof—peripheral folding is a related feature in Mull. Cone-sheet complexes are extensively developed in Skye, Mull and Ardnamurchan. The Skye, Rum, Mull and Arran centres have crowded dyke-swarms. The general dyke-direction is north-westerly, but this is combined with a radial tendency in Rum. Some believe that most of the Hebridean lavas were fed from dykes (fissure eruptions). It is certain, however, that the great centres were established before the dyke-swarms, since they locate the latter. It is also certain that most of the dykes are later than any lavas spared by erosion.
West Highland scenery has been shaped entirely since the early Tertiary eruptions. The magnificent mountain and valley forms of Skye are cut in Tertiary plutonics.
Possible Pliocene gravel occurs near Turriff, Fyvie and in Cen tral Buchan, all in Aberdeenshire.
Pleistocene and Recent.—.During the Glacial Period, Scot land functioned as a complex centre of dispersal within the great North European ice-sheet. Scandinavian currents were almost ex cluded except in Shetland, whilst Scottish currents freely invaded England. Some districts were crossed by ice that traversed the sea-bed bringing in shells and, in Caithness, Mesozoic erratics. Glacial erosion is often pronounced. Crag and tail is developed to perfection in Edinburgh and elsewhere. Rock basins are numerous in the Highlands, with Loch Coruisk as a diagrammatic example. Characteristic deposits are: West Highlands, hummocky mo raines; East Highlands, fluvio-glacial gravel; Lowlands, boulder clay, either flat or in drumlins, and gravel kames. In Glen Roy glacially dammed lakes are recorded by conspicuous strand-lines, and throughout most of eastern Scotland glacially diverted rivers can be traced by channels now left dry.
Raised beaches up to about ioo ft. occur round Scotland, but not in the Outer Hebrides, Orkneys and Shetlands. The higher beaches are late Glacial and are locally interfered with by glacial readvance (Loch Lomond and Mull). The best marked beach, often about 3o ft., has a temperate fauna. It rests in places on a peat or forest bed that continues below sea-level. Traces of early man are found in this raised beach. (E. B. B.) Vegetation.—Geographical usage places Scotland within the cool-temperate forest division of the Northern Hemisphere, but in doing so implies no more than that Scotland lies between those latitudes within which neither arctic nor sub-tropical vegetation is characteristic, and that the conditions are those of a land under maritime, not interior-continental, climatic influence. Actually forests—extensive tree-covered areas, as distinct from the tree less "deer forests" of Scottish phrase—are practically absent in Scotland; wooded tracts are of no great extent and are scattered, save in so far as they appear mainly upon the eastern and southern borders of the Highlands. They consist mostly of conifers and oaks. Native species are few. Apart from destruction by man (which has in some measure been offset by planting) it is clear that Scotland, separated from Europe relatively soon after the final glacial epoch, was poorly colonized by north-European species of trees. A damp climate, imperfect drainage and wet soil, and un favourable exposure to prevalent winds over wide areas, are fur ther reasons adduced for the poverty of the growth. The upper limit of trees lies about 2,000ft. above sea-level in the southern Uplands, and somewhat below that height (1,7oo–I,gooft.) in the central Highlands ; farther north, it falls to 1,200-1,400ft. in cen tral Sutherland, and lower still in the extreme north. Types of vegetation in the Highlands may in a measure be localized. Thus, peat moors of wide extent occur in definite areas—in Sutherland and Caithness most notably; also, in the south, on the moor of Rannoch and about Lochs Awe and Etive, between the heads of Lochs Fyne and Lomond, and to the east of Callander, and on the long eastern flanks of the region. Marshy grass lands have a wider extent in the west than in the east, in sympathy with the higher rainfall of the west; they are interspersed with drier mountain and pasture lands, usually at higher levels, with better drainage on the steeper slopes; while a definitely drier type of moorland occurs at lower levels in the north-west and on the outer islands, where the surface is much broken. Heath moors, as distinct from grass moors, occur widely both in the Highlands and on the southern Upland, but they are by far the more characteristic on the east side of the Highlands generally than on the west, and especially on the Grampian heights. The wide expanse of grassy hill-pasture on the southern uplands has al ready been mentioned, and indications have been given of the distribution of agricultural lands in the respective regional divi sions. But the main localization of agricultural lands may be indicated briefly as occurring in an eastern belt following the curves of the coast between the Firths of Dornoch and Forth, with some extension north of the first and south of the second; for the rest, such lands, except in the non-industrial parts of the central Lowlands and in the dales and on the western slopes of the southern Uplands, are strictly limited in area. At certain points on all the coasts, but most notably the east, extensive sand-dunes, with their characteristic vegetation, are found. Finally, reference is due to the alpine and arctic types of plants, such as saxifrages and mountain willow, which are common on Highland summits above some 2,000f t. of elevation, though Ben Lawers (3,982ft.), above Loch Tay, is usually cited as offering examples of particular interest.