The Ancient Volcanoes of Great Britain, Volume 1 (of 2)

Underground Phases of Volcanic Action. B. Materials injected or consolidated beneath the Surface--Intrusive Series: I. Vents of Eruption--i. Necks of Fragmentary Materials; ii....

1. Bedded Lavas and Tuffs; Upper Limits and Original Areas and Slopes of the Plateaux; 2. Vents; Necks of Agglomerate and Tuff; Necks of Massive Rock; Composite Necks; 3. Dykes...

I now propose to give some account of each of the districts which have been separate areas of volcanic action during the time of the Lower Old Red Sandstone, tracing its general...

old volcanoes above described has, in Britain, its accompaniment of dykes and veins. The plateaux, however, present by far the most abundant and varied development of them. The...

Abundant as are the volcanic records of the Silurian period in England, Wales and Scotland, the description of them would be incomplete without an account of those of Ireland. T...

We have now to note the leading features of the groups of volcanic rocks distributed along the southern line of vents already described. At least four different centres of erupt...

Placing the upper limit of the Cambrian system at the top of the Tremadoc group, we pass into the records of another series of volcanic eruptions which marked various epochs dur...

The Cambrian volcanic rocks in the northern part of the Welsh Principality have their main development in Caernarvonshire. Southwards from that tract, though the Lower Cambrian...

From the time of the appearance of Sedgwick's classic letters to Wordsworth, no volcanic area of Britain has probably been so well known in a general sense to the ordinary trave...

In the southern part of the Principality of Wales a remarkably varied display of British Cambrian volcanic rocks has been preserved. The district around St. David's has the dist...

In the south-east of Scotland, and extending thence into the north of England, the remains of several distinct volcanic centres of the Lower Old Red Sandstone may still be recog...

age in Central Scotland, where a basic lava can sometimes be proved to be a true flow and not an intrusive sill by the fact that portions of its upper slaggy surface are enclose...

Owing to the effects partly of plication and partly of denudation, the rocks of the next volcanic episode in Wales, that of the Bala period, occupy a less compact and defined ar...

Geography and Scenery of the Carboniferous Period--Range of Volcanic Eruptions during that time--I. The Carboniferous Volcanoes of Scotland--Distribution, Arrangement and Local...

Though many of the geological details of each of the Scottish districts of Puys have been given in the foregoing pages, it will be of advantage to describe in connected sequence...

One of the characteristic features of Central Scotland is the great number, and often the large size and extraordinary persistence, of the masses of eruptive, more or less basic...

From the centre of England we must in imagination transport ourselves into the Southern Uplands of Scotland, where a widely distributed series of Silurian volcanic rocks has bee...

Earliest Knowledge of Volcanoes--Their Influence on Mythology and Superstition--Part taken by Volcanic Rocks in Scenery--Progress of the Denudation of Volcanoes--Value of the Re...

Among the thick group of sedimentary formations which overlies the great volcanic ridge of the Arans and Arenig, and undulates eastwards across the Bala Valley, occasional thin...

The British Isles are singularly fortunate in possessing an admirable development of pre-Cambrian rocks. These ancient masses rise up in various parts of the islands, but the re...

We now enter upon the consideration of the records of a notable era in the geological evolution of north-western Europe. Up to the close of the Silurian period the long history...

As considerable popular misapprehension exists respecting the part which volcanism has played in the evolution of the existing topography of the earth's surface, and as the Brit...

A general summary of the petrographical characters of the igneous rocks of the Lower Old Red Sandstone may here find a place. Further details will be given in the account of "La...

1. _The Vesuvian Type._--In this kind of volcano, lavas and fragmental ejections are discharged from a central vent, which is gradually built up by successive eruptions of these...

Notwithstanding the effects of many powerful faults and extensive denudation, the general position of the Plateaux and their independence of each other can still be traced. They...

The coarser fragmentary materials thrown from volcanic vents are known as Agglomerates where they show no definite arrangement, and especially where they actually fill up the ol...

We have now to consider the nature of the materials erupted by the volcanic activity of the puys. The geologist who passes from the study of the plateau lavas to those of the pu...

A large number of vents rise through the Carboniferous rocks of Scotland. Some of these are not associated with any interbedded volcanic material, so that their geological age c...

In leaving the investigation of the pre-Cambrian rocks and entering upon that of the Palæozoic systems, that is, the great series of sedimentary formations which include the ear...

Throughout the whole region of the British Isles, wherever the uppermost strata of the Silurian system can be seen to graduate into any later series of sedimentary deposits, the...

On a nearer inspection, the dominant topographical features are found to correspond with a well-marked stratification of the whole volcanic series. Where two sheets of andesite...

During at least the earlier part of the period of the puys, in some districts or from certain vents, such as those of East Fife, Western Midlothian, Eastern Linlithgowshire, Nor...

We now come to one of the great gaps in the geological record. The Lewisian gneiss affords us glimpses of probable volcanic activity at the very beginning of geological history....

74. Craig Beinn-nan-Eun (2067 feet), east of Uam Var, Braes of Doune. Old Red Conglomerate, with the truncated ends of the strata looking across into the Highlands; moraines of...

Along the eastern borders of Wales a ridge of ancient rocks, much broken by faults and presenting several striking unconformabilities, has long been classic ground in geology fr...

In the northern half of Britain, where the Old Red Sandstone is so well displayed, the two great divisions into which this series of sedimentary deposits is there divisible are...

A volcano is a conical or dome-shaped hill or mountain, consisting of materials which have been erupted from an orifice leading down from the surface into the heated interior of...

Of these basic lavas conspicuous examples may be seen at Arthur Seat, Calton Hill and Craiglockhart Hill. The eastern part of Arthur Seat, known as Whinny Hill, furnishes exampl...

In the heart of England the great Triassic plain is diversified by the uprise through it of the peaks and crests of an old Triassic land-surface, which are embraced in the distr...

On the whole the actual vents of the volcanoes of Lower Old Red Sandstone time are less clearly distinguishable than those of subsequent volcanic periods. This deficiency doubtl...

In the island of Anglesey an interesting series of schists and quartzites presents many points of resemblance to the Dalradian or younger schists of the Highlands. At present th...

Underground Phases of Volcanic Action--_continued_. II. Subterranean Movements of the Magma: i. Dykes and Veins; ii. Sills and Laccolites; iii. Bosses (Stocks, Culots)--Conditio...

After the beginning of the Carboniferous Limestone period, when eruptions of the plateau-type had generally ceased, volcanic activity showed itself over the area of the British...

While the materials erupted from old volcanic vents tell plainly enough their subterranean origin, they may leave us quite in the dark as to the conditions under which they were...

The next great geological period, to which Murchison gave the name of Silurian, has in Britain a fuller record than the period which preceded it. The rocks that tell its history...

The Beginnings of Geological History--Difficulties in fixing on a generally-applicable Terminology--i. The Lewisian (Archæan) Gneiss; ii. The Dalradian or Younger Schists of Sco...

In north-western Pembrokeshire, the observations of Murchison, De la Beche and Ramsay showed the existence of an important volcanic district, where numerous igneous bands are in...

The term Lava is a convenient and comprehensive designation for all those volcanic products which have flowed out in a molten condition. They differ from each other in compositi...

The area within which volcanic rocks belonging to the Lower Old Red Sandstone appear is one of the most extensive regions over which the volcanic eruptions of any geological per...

So far as the available evidence goes, the most important volcanic centre down the eastern side of Wales during the Llandeilo period was one which lay not far from the centre of...

Nowhere throughout the volcanic tracts of the Lower Old Red Sandstone is there any such development of sills as may be seen beneath the Silurian volcanic sheets of North Wales....

i. The Builth Volcano--ii. The Volcanoes of Pembrokeshire--iii. The Caernarvonshire Volcanoes of the Bala Period--iv. The Volcanic District of the Berwyn Hills--v. The Volcanoes...

About 35 miles to the south-east of the great volcanic range of Merionethshire a small tract of Arenig rocks rises from amidst younger formations, and forms the picturesque coun...

In themselves, accumulations of volcanic materials do not furnish any exact or reliable evidence of the geological period in which they were erupted. The lavas of the early Palæ...

The volcanic materials characteristic of the plateau-type of eruptions consist mainly of lavas in successive sheets, but include also various tuffs in frequent thin courses, and...

1. Vents: Relation of the Necks to the Rocks through which they rise--Evidence of the probable Subærial Character of some of the Cones or Puys of Tuff--Entombment of the Volcani...

We have now to consider the manner in which the various volcanic products have been grouped around and within the orifices of discharge. The first feature to arrest the eye of a...

In the division of the Plateaux I group all the more copious eruptions during the Carboniferous period, when the fragmentary materials generally formed but a small part of the d...

Materials erupted at the Surface--Extrusive Series--_continued_. iii. Types of old Volcanoes--1. The Vesuvian Type; 2. The Plateau or Fissure Type; 3. The Puy Type. iv. Determin...

Ancient Volcanoes: Proofs of their existence derived from the Nature of the Rocks erupted from the Earth's Interior. A. Materials erupted at the Surface--Extrusive Series. i. La...

Underground Phases of Volcanic Action. B. Materials injected or consolidated beneath the Surface--Intrusive Series: I. Vents of Eruption--i. Necks of Fragmentary Materials; ii....

1. Vents: Relation of the Necks to the Rocks through which they rise--Evidence of the probable Subærial Character of some of the Cones or Puys of Tuff--Entombment of the Volcani...

i. The Builth Volcano--ii. The Volcanoes of Pembrokeshire--iii. The Caernarvonshire Volcanoes of the Bala Period--iv. The Volcanic District of the Berwyn Hills--v. The Volcanoes...

The Beginnings of Geological History--Difficulties in fixing on a generally applicable Terminology--i. The Lewisian (Archæan) Gneiss; ii. The Dalradian or Younger Schists of Sco...

Geography and Scenery of the Carboniferous Period--Range of Volcanic Eruptions during that time--I. The Carboniferous Volcanoes of Scotland--Distribution, Arrangement and Local...

1. Bedded Lavas and Tuffs; Upper Limits and Original Areas and Slopes of the Plateaux; 2. Vents; Necks of Agglomerate and Tuff; Necks of Massive Rock; Composite Necks; 3. Dykes...

Materials erupted at the Surface--Extrusive Series--_continued_. iii. Types of old Volcanoes--1. The Vesuvian Type; 2. The Plateau or Fissure Type; 3. The Puy Type. iv. Determin...

Earliest Knowledge of Volcanoes--Their Influence on Mythology and Superstition--Part taken by Volcanic Rocks in Scenery--Progress of the Denudation of Volcanoes--Value of the Re...

Ancient Volcanoes: Proofs of their existence derived from the Nature of the Rocks erupted from the Earth's Interior. A. Materials erupted at the Surface--Extrusive Series. i. La...

Underground Phases of Volcanic Action--_continued_. II. Subterranean Movements of the Magma: i. Dykes and Veins; ii. Sills and Laccolites; iii. Bosses (Stocks, Culots), Conditio...