Volcanic Sentence Examples

The islands are, indeed, plainly volcanic in their nature.

Its fires are not volcanic, but result from the combustion of coal some distance underground, giving off much smoke and steam; geologists estimate that the burning has been going on for at least 800 years.

In connection with the volcanic districts we may mention Le Mofete, the pools of Ampsanctus, in a wooded valley S.E.

But it is notable that all recent volcanic action was confined to a wide belt parallel to the coast.

Numerous warm springs are scattered about this volcanic region.

Lava is much used for paving-stones in the neighborhood of volcanic districts, where pozzolana (for cement) and pumice stone are also important.

Of these Ischia and Procida, close to the northern headland of the Bay of Naples, are of volcanic origin, as is the case also with the more distant group of the Ponza Islands.

North of the fiftieth parallel the depths diminish towards the north-east, two long submarine ridges of volcanic origin extend north-eastwards to the southwest of Iceland and to the Faeroe Islands, and these, with their intervening valleys, end in a transverse ridge connecting Greenland, through Iceland and the Faeroe Islands, with Northwestern Scotland and the continental mass of Europe.

Equally indecisive is the further exploration as to evidence for the opinion held by other naturalists that the endemic species of the different islands have resulted from subsidences, through volcanic action, which have reduced one large island mass into a number of islets, wherein the separated species became differentiated during their isolation.

The Tertiary deposits cover the whole of the central depression, where they are associated with extensive flows of lava and beds of volcanic ash.

Contemporaneous volcanic rocks are associated with the Ordovician beds and with the Rhaetic sandstones in several places.

The Aeolian or Lipari Islands, a remarkable volcanic group, belong rather to Sicily than to Italy, though Stromboli, the most easterly of them, is about equidistant from Sicily and from the mainland.

Jurassic Oeuonian Volcanic Rock, country was free from outbursts, except in the regions of the Alps and Pyrenees.

Similar deposits, of approximately the same age, occur in Tasmania and New Zealand; and at about the same time there began the Kainozoic volcanic period of Australasia.

Professor Suess, to whom the above description is due, finds that the Mediterranean forms no exception to the rule in affording no evidence of elevation or depression within historic times; but it is noteworthy that its present basin is remarkable in Europe for its volcanic and seismic activity.

It contains many mountains volcanic in origin (Plomb du Cantal, Puy de Dome, Mont Dore), fertile valleys such as that of Limagne, vast pasturelands, and numerous medicinal springs.

Besides these, and leaving out of account the islands, the Italian peninsula presents four distinct volcanic districts.

The volcanic region of the Terra di Lavoro is separated by the Volscian mountains from the Roman district.

The Apulian volcanic formation consists of the great mass of Monte Volture, which rises at the west end of the plains of Apulia, on the frontier of Basilicata, and is surrounded by the Apennines on its south-west and north-west sides.

The Hauraki Gulf, a great square inlet opening northward, is studded with islands of considerable elevation; Rangitoto, which protects the harbour, is a volcanic cone reaching nearly l000 ft.

The volcanic soil is highly fertile.

This place may either be a point, as in a volcanic cone, or a line, as in a mountain range or ridge of hills.

A region where volcanic activity has led to the embedding of dykes or bosses of hard rock amongst softer strata produces a plain broken by abrupt and isolated eminences.'

Volcanic sulphur usually occurs as a sublimate around or on the walls of the vents, and has probably been formed in many cases by the interaction of sulphur dioxide and hydrogen sulphide.

It was formerly believed that the sulphur had a volcanic origin, but it is now generally held that it has either been reduced from gypsum by organic agencies, or more probably deposited from sulphur-bearing waters.

It is of Tertiary formation (Miocene), and has a chain of volcanic elevations along the axis, reaching a height of 2600 ft.

It consists of a single mountain mass (volcanic in origin), 18 m.

It is conjectured that at some remote period the Hawash flowed into Tajura Bay and that the present condition of the country is the result of volcanic upheaval.

Thera is also of special interest to geologists owing to its remarkable volcanic phenomena.

The mineral wealth of the Cyclades has hitherto been much neglected; iron ore is exported from Seriphos, manganese and sulphur from Melos, and volcanic cement (pozzolana) from Santorin.

In the western portion of Mainland, in Northmavine, -there is a considerable tract of rocks of this age which are formed largely of intrusive diabase-porphyrite; similar volcanic rocks occur in Papa Stour.

Volcanic in origin - the Jebel ed-Druz is a group of extinct volcanoes - the friable volcanic soil is extraordinarily fertile.

In the original formation of the island volcanic disturbances and coral growth played some part; but there are only very slight superficial evidences in the island of former volcanic activity.

The northern, as in Bali and Lombok, is of volcanic origin.

Between these two chains are round hills consisting of lavas or sometimes of volcanic tuffs, covered with the long silvery grass which also clothes vast prairies in Java and Sumatra.

It is of volcanic origin, and is partly occupied by a penal agricultural colony.

An effect of the greater tide-generating force will also be instability of the liquid magmas underlying volcanic areas, leading to violent eruptions and earthquakes.

Like the rest of the cluster, the island is of volcanic origin, with tuff, trachyte and obsidian among its ordinary rocks.

See Leycester, "The Volcanic Group of Milo, Anti-Milo, &c.," in Jour.

Although rocks wholly or in large part vitreous are known from very ancient geological systems, such as the Devonian, they are certainly most frequent in recent volcanic countries.

The archipelago is of volcanic formation, Tamara and Factory islands forming part of a ruined crater, with Crawford Island as the cone.

Volcanic formations, so far as is known, occur chiefly along the north-western border-range of the great plateau.

Lead chloride, PbC1 2, occurs in nature as the mineral cotunnite, which crystallizes in the rhombic system, and is found in the neighbourhood of volcanic craters.

The central Cevennes, comprising the volcanic chain of Vivarais, incline south-east and extend as far as the Lozere group. The northern portion of this chain forms the Boutieres range.

The greater part is a rock destitute of soil, and presenting the wildest aspect; the ground is cold, poor and sterile; and the whole face of the country bears marks of volcanic action.

He made researches on volcanic phenomena, especially on the gaseous emanations.

Eruptive rocks occur in the Devonian and Carboniferous beds, but there is no evidence of volcanic activity since the Palaeozoic epoch.

Amongst the most interesting features of the Bakony-wald are the volcanic and the igneous rocks.

Syenites, gabbros, norites and volcanic rocks are also represented.

It attracts many visitors both as a health resort and on account of the magnificent scenery and remarkable volcanic phenomena of the surrounding district.

The very extensive pumice deposits at Neuwied and the lava and other volcanic rocks belong to a more recent epoch.

The vast works for the refining of sulphur in the volcanic district of Solfatara were erected under his direction.

Volcanic rocks are not common in any part of Burma, but about 50 m.

Whether the mud " volcanoes" of the Irrawaddy valley have any connexion with volcanic activity may be doubted.

Grape-stones have been found among the remains of Swiss and Italian lake dwellings of the Bronze period, and others in tufaceous volcanic deposits near Montpellier, not long before the historic era.

The soil is mainly of volcanic origin.

It includes chalky limestones, siliceous earths, red clay, and, at the top, a layer of mudstone composed mainly of volcanic dust.

The greater portion of this region is an open steppe, sandy in places and in others dotted with low volcanic hills, but with occasional ground water and in favourable seasons furnishing support for a considerable pastoral population.

Volcanic cones still exist in large numbers, and the sheets of lava appear as fresh as any recent flows of Etna or Vesuvius.

An extinct volcano occurs at Aden, and volcanic rocks are found at other places near the Straits of Bab-el-Mandeb.

It is, however, a region of past volcanic activity, and these salt depressions may be due to that cause.

In 1819, in the course of a tour through France, he made the volcanic district of Auvergne a special study, and his Letters on the Volcanos of Auvergne were published in The Edinburgh Journal, 1820-21.

By subsequent journeys in Hungary, Transylvania, Italy, Sicily, France and Germany he extended his knowledge of volcanic phenomena; and in 1826 the results of his observations were given in a work entitled A Description of Active and Extinct Volcanos (2nd ed., 1848).

The Western Cordillera, overhanging the Peruvian coast, contains a long line of volcanic mountains, most of them inactive, but their presence is probably connected with the frequent and severe earthquakes, especially in the southern section of the coast.

It contains a regular chain of volcanic peaks overlooking the coastregion of Tarapaca.

In rear of Moquegua there is a group of volcanic peaks, clustering round those of Ubinas and Huaynaputina.

The Central Cordillera consists mainly of crystalline and volcanic rocks, on each side of which are aqueous, in great part Jurassic, strata thrown up almost vertically.

It is nowhere disturbed by volcanic eruptions, except at the very edge of the formation near Lake Titicaca, and in this respect it differs essentially from the Maritime Cordillera.

Geology.'--The Eastern Cordillera., which, however, is but little known, appears to consist, as in Bolivia, chiefly of Palaeozoic rocks; the western ranges of the Andes are formed of Mesozoic beds, together with recent volcanic lavas and ashes; and the lower hills near the coast are composed of granite, syenite and other crystalline rocks, sometimes accompanied by limestones and sandstones, which are probably of Lower Cretaceous age, and often covered by marine Tertiary deposits.

In the Cordillera Nevada the Mesozoic rocks which form the chain are often covered by masses of modern volcanic rock.

Similar rocks are also found in the Cordillera Negra, but the volcanic centres appear to have been in the Sierra Nevada.

Hence the mountain has served as a type for the general popular conception of a volcano, and its history has supplied a large part of the information on which geological theories of volcanic action have been based.

At the beginning of the Christian era, and for many previous centuries, no eruption had been known to take place from the mountain, and the volcanic nature of the locality was perhaps not even suspected by the inhabitants who planted their vineyards along its fertile slopes, and built their numerous villages and towns around its base.

The geographer Strabo, however, detected the probable volcanic origin of the cone and drew attention to its cindery and evidently fire-eaten rocks.

But towards the top the upward growth of vegetation had not concealed the loose ashes which still remained as evidence of the volcanic nature of the place.

But the bundant steam given off by the volcano seems to have con- c ensed into copious rain, which, mixing with the light volcanic V

Lofty summits are separated by comparatively low passes, which lie at the level of crystalline rocks and schists constituting the original uplands upon which the summits have been piled by volcanic action.

A little farther south enclosing the fertile plain of Aizu (Aizu-taira, as it is called) several important peaks are found, among them being lide-san (6332 ft.) Azuma-yama (7733 ft.), which, after a long interval of quiescence, has given many evidences of volcanic activity during recent years; Nasu-dake (6296 ft.), an active volcano; and Bandai-san (6037 ft.), A terrible interest attaches to the last-named mountain, for, after having remained quiet so long as to lull the inhabitants of the neigh.

Among the mountains, of Japan there are three volcanic ranges, namely, that of the Kuriles, that of Fuji, and that of Kirishima.

Volcanoes Fuji is the most remarkable volcanic peak.

The only remaining active vent of the once highly volcanic Nikko district.

Two of the five compartments into which it is divided by walls of deeply striated volcanic ash are constantly emitting steam, while a new vent displaying great activity has been opened at the base of the cone on the south side.

Some are contained in alluvial depressions in the river valleys; others have been formed by volcanic eruptions, the ejecta damming the rivers until exits were found over cliffs or through gorges.

Geology.It is a popular belief that the islands of Japan consist for the most part of volcanic rocks.

Between the two zones lies a row of Klippen, while towards the Hungarian plain the inner zone is bordered by a fringe of volcanic eruptions of Tertiary age.

Of all the peculiar features of the Carpathian chain, perhaps the most remarkable is the fringe of volcanic rocks which lies along its inner margin.

It is generally considered to have been formed by a volcanic explosion at the margin of the great crater of the Albanus Mons; it has the shape of a crater, the banks of which are over 400 ft.

Cactaceae belong almost entirely to the New World; but some of the Opuntias have been so long distributed over certain parts of Europe, especially on the shores of the Mediterranean and the volcanic soil of Italy, that they appear in some places to have taken possession of the soil, and to be distinguished with difficulty from the aboriginal vegetation.

It is entirely of volcanic origin, and about 45 sq.

Hot mineral springs and ebullitions of steam still testify to the presence of volcanic activity.

The island is in part of volcanic formation, and the existence of hot springs points to volcanic activity.

Particularly steep slopes are found in the case of submarine domes, usually incomplete volcanic cones, and there have been cases in which after such a dome has been discovered by the soundings of a surveying ship it could not be found again as its whole area was so small and the deep floor of the ocean from which it rose so flat that an error of 2 or 3 m.

While such steep mountain walls are found in the bed of the ocean it must be remembered that they are very exceptional, and except where there are great dislocations of the submarine crust or volcanic outbursts the forms of the ocean floor are incomparably gentler in their outlines than those of the continents.

From the floor of this vast and profound depression numerous isolated volcanic cones rise with abrupt slopes, and even between the islands of the Hawaiian group there are depths of more than 2000 fathoms. The Society Islands and Tahiti crown a rise coming within 150o fathoms of the surface, two similar rises form the foundation of the Paumotu group where Agassiz found soundings of.

In the form of volcanic mud it is common round the high volcanic islands of the SouthWestern Pacific.

As well as the finest of terrigenous clay there is present in sea-water far from land a different clay derived from the decomposition of volcanic material.

Volcanic dust thrown into the air settles out slowly, and some of the products of submarine and littoral volcanoes, like pumice-stone, possess a remarkable power of floating and may drift into any part of the ocean before they become waterlogged and sink.

The dredge often brings up large numbers of nodules formed upon sharks' teeth, the ear-bones of whales or turtles or small fragments of pumice or other volcanic ejecta, and all more or less incrusted with manganese oxide until the nodules vary in size from that of a potato to that of a man's head.

It is, however, a curious question how, considering the increase of carbonic acid by the decomposition of organic bodies and possible submarine exhalations of volcanic origin, the water has not in some places become saturated and a precipitate of amorphous calcium carbonate formed in the deepest water.

The great similarity between the salts of the ocean and the gaseous products of volcanic eruptions at the present time, rich in chlorides and sulphates of all kinds, is a strong argument for the ocean having been salt from the beginning.

The amount of carbonic acid in solution may also be increased by submarine exhalations in regions of volcanic disturbance, but it must be remembered that the critical pressure for this gas is 73 atmospheres, which is reached at a depth of 400 fathoms, so that carbonic acid produced at the bottom of the ocean must be in liquid form.

The town slopes to the ocean, with a background of forest surmounted by the snow-clad volcanic cone of Mount Egmont (8270 ft.).

An anthracite occurring in connexion with the old volcanic rocks of Arthur's Seat,Edinburgh, which contains a large amount of sulphur in proportion to the Caking coals.

The soil is of volcanic origin (trachyte).

The catastrophe has been explained as a volcanic eruption, or an explosive outburst of gas and oil stored and accumulating at high pressure.

The volcanic plateau of British East Africa extends over the boundary in the region of Kilimanjaro.

The geography of the Western province includes many interesting features, the in many ways peculiar Albert Nyanza (q.v.), the great snowy range of Ruwenzori (q.v.), the dense Semliki, Budonga, Mpanga and Bunyaraguru forests, the salt lakes and salt springs of Unyoro and western Toro, the innumerable and singularly beautiful crater lakes of Toro and Ankole, the volcanic region of Mfumbiro (where active and extinct volcanoes rise in great cones to altitudes of from 11,000 to nearly 15,000 ft.), and the healthy plateaus of Ankole, which are in a lesser degree analogous in climate and position, and the Nandi plateau on the east of Victoria Nyanza.

Volcanic rocks occur in Usoga and elsewhere.

The rocks on the verge of the Kisumu province of East Africa are mainly volcanic (basalt, tuff, lava, kenyte).

West of the volcanic region, nearer to Lake Victoria and the Eastern province, ironstone, granite, gneiss and schistose formations predominate, with phonolite in places.

In the Rudolf province there and are the basalt, lava, tuff and kenyte of the volcanic mineralogy.

The volcanic d'Entrecasteaux Islands are mostly larger, more elevated (the highest being 8000 ft.), and stand in deeper water than the Louisiade group. To the east of Kiriwina (Trobriand) lies a small group of uniquely formed islets, each of which is completely surrounded by a steep forest-clad marginal rampart of coral 300 to 400 ft.

The volcanic series include the rhyolite of Nell Island, some obsidian, and the sheets of basalts which form the Cloudy Mountains, Mount Dayman and Mount Trafalgar (an active volcano), and also cover wide areas to the south and west of the Owen Stanley Range.

It appears to consist in the main of a continuation of an axis of old schists and slates, with granite intrusions, and flanked by coastal plains with Cretaceous or Jurassic, and Miocene beds, with Pleistocene sands and reefs and volcanic rocks.

In Rossel Island (Roua or Arova) occur crystalline schistose and volcanic rocks, and in Misima (St Aignan) limestones and lavas in addition.

North and north-west the lake is closed in by the volcanic Buru hills; to the south towers the extinct volcano of Longonot.

In Mexico, Colombia and Peru the cutting of friable stone with tough volcanic hammers and chisels, as well as rude metallurgy, obtained, but the evidences of smelting are not convincing.

The same objection to over-massiveness might not apply here as in Mexico, owing to volcanic activity.

They are apparently volcanic. Coral reefs lie off the coasts and render them difficult of access.

Kerguelen Island is of undoubted volcanic origin, the prevailing rock being basaltic lavas, intersected occasionally by dikes, and an active volcano and hot springs are said to exist in the south-west of the island.

Judging from the abundant fossil remains of trees, the island must have been thickly clothed with woods and other vegetation of which it has no doubt been denuded by volcanic action and submergence, and possibly by changes of climate.

The Aucklands contain two of the finest harbours in the Pacific. Six hundred miles north of Auckland, the volcanic Kermadecs, covering 8208 acres, are picturesquely clothed with vegetation.

The dominating features of south New Zealand are not ferny plateaus or volcanic cones, but stern chains of mountains.

It has, moreover, been a volcanic area of long-continued activity.

Suess therefore suggested that the northern continuation of the Alps had foundered, and its summits been buried beneath the Pliocene marine rocks of the Wanganui basin and the volcanic rocks of the Taupo area.

The Cainozoic volcanic history of New Zealand begins in the Oligocene, when the high volcanic domes of Dunedin and Banks Peninsula were built up. The Dunedin lavas including tephrites and kenytes correspond to the dacite eruptions in the volcanic history of Victoria.

The volcanic activity of the Taupo district lasted into the Pleistocene, and the last eruptions contributed many of its chief geographical features.'

The soils of western Washington are chiefly glacial, those of eastern Washington chiefly volcanic. In the low tidewater district of the Puget Sound Basin an exceptionally productive soil has been made by the mixture of river silt and sea sand.

On the Columbia plateau the soil is principally volcanic ash and decomposed lava; it is almost wholly volcanic ash in the more arid sections, but elsewhere more decomposed lava or other igneous rocks, and some vegetable loam is mixed with the ash.

Its northern shores are bordered by the beautiful basaltic cones of the Bakony mountains, the volcanic soil of which produces grapes yielding excellent wine; the southern consist partly of a marshy plain, partly of downs.

The Malakatyntras is also made up of volcanic rocks.

It is the chief place in the Tolfa Mountains, an extinct volcanic group between Civitavecchia and the Lake of Bracciano.

From the falls to McCarthy's Island, a distance of 200 m., the river valley, which here presents a park-like appearance, is enclosed by low rocky hills of volcanic character.

Several quiescent volcanic peaks, reaching 5700 ft., occupy most of the island, and are covered with forests.

Tuff and travertine are calcareous deposits found in volcanic districts.

This acid is exhaled in volcanic gas, which is passed through water tanks.

Ammonia is found in small quantities as the carbonate in the atmosphere, being produced from the putrefaction of nitrogenous animal and vegetable matter; ammonium salts are also found in small quantities in rain-water, whilst ammonium chloride (sal-ammoniac) and ammonium sulphate are found in volcanic districts; and crystals of ammonium bicarbonate have been found in Patagonian guano.

In the vicinity of the Ullughmuz-tagh there exist numerous indications of former volcanic activity, the eminences and summits frequently being capped with tuff, and smaller fragments of tuff are scattered over other parts of the Arka-tagh ranges.

The volcanic fissures that allowed of the upwelling of basalt are represented by numerous dykes, many cutting the earlier lava-flows as well as all the beds below them.

Volcanic necks may be recognized at Carrick-a-rede, in the intrusive mass of dolerite at Slemish, at Carnmoney near Belfast, and a few other points.

The island is of volcanic formation and mountainous, the highest summit being Beerenberg in the north (8350 ft.).

Volcanic eruptions have been observed.

Carbon monoxide, CO, is found to some extent in volcanic gases.

It is a regular constituent of the atmosphere, and is found in many spring waters and in volcanic gases; it also occurs in the uncombined condition at the Grotto del Cane (Naples) and in the Poison Valley (Java).

Among the Tertiary volcanic rocks those of acid types (granites, granulites) were the first to appear and are developed latitudinally; rocks of intermediate type (dacites, andesites) characterize the Miocene and early Pliocene periods; while the basic rocks (ophites, elaeolite syenites and basalts) attained their maximum in later Pliocene and Quaternary times.

The average depth varies from 1500 to 2500 fathoms, and from this level innumerable volcanic ridges and peaks rise almost or quite to the surface, their summits for the most part occupied by atolls and reefs of coral formation, while interspersed with these are depressions, mostly of small area, among which the deepest soundings recorded have been obtained.

It is impossible to estimate the total number of the islands; an atoll, for instance, which may slate in the Marquesas, which afford a type of the extinct volcanic islands, as does Tahiti.

In other areas, however, there is still volcanic activity, and in many cases volcanoes to which only tradition attributes eruptions can hardly be classified as extinct.

Earthquakes are not uncommon in the volcanic areas.

Most of the volcanic islands are lofty in proportion to their size.

The islands may be divided broadly into volcanic and coral islands, though the physiography of many islands is imperfectly known.

There are ancient rocks, however, in New Caledonia, which .has a geological affinity with New Zealand; old sedimentary rocks are known in New Pomerania, besides granite and porphyry, and slates, sandstone and chalk occur in Fiji, as well as young volcanic rocks.

Here the broad distinction has been drawn between volcanic and coral islands; but this requires amplification, both because the coral islands follow more than one type, and because the work of corals is in many cases associated with the volcanic islands in the form of fringing or barrier reefs.

As to the distribution of coral reefs within the Pacific area, in Micronesia the northern Marianas (volcanic) are without reefs, which, however, are well developed in the south.

In Melanesia, as has been seen, the volcanic type predominates.

Of the Polynesian Islands, the Hawaiian chain presents the type of a volcanic group through which coral reefs are not equally distributed.

Round the volcanic Marquesas Islands, again, coral is scanty, but the Society Islands, Samoa and Tonga have extensive reefs.

As to the local distribution of reefs, it has been maintained that in the case of active volcanic islands which have no reefs, their absence is due to subterranean heat.

In considering the flora of the islands it is necessary to distinguish between the rich vegetation of the fertile volcanic islands and the poor vegetation of the coral islands.

In the volcanic islands a distinction may be observed between the windward and leeward flanks, the moister windward slopes being the more richly clothed.

The soil in the valleys is volcanic and fertile, but the gradual utilization of natural timber increases the liability to drought, as there are no streams. The climate is variable and rainy.

Two volcanic Cordilleras or mountain chains, separated from one another by the central plateau of San Jose and Cartago, traverse the interior of Costa Rica, and form a single watershed, often precipitous on its Pacific slope, but descending more gradually towards the Atlantic, where there is a broad expanse of plain in the north-east.

The more northerly range, in which volcanic disturbances on a great scale have been comparatively recent, extends transversely across the country, from a point a little south of Salinas Bay, to the headland of Carreta, the southern extremity of the Atlantic seaboard, also known as Monkey Point.

At first it is rather a succession of isolated volcanic cones than a continuous ridge, the most conspicuous peaks being Orosi (5185 ft.), the four-crested Rincon de la Viej a (4500), Miravalles (4698) and Tenorio (6800).

Throughout the volcanic area earthquakes and landslides are of frequent occurrence.

The special adaptability of this region to its growth is attributed to the nature of the soil, which consists of layers of black or dark-brown volcanic ash, varying in depth from 1 to 6 yds.

The geological formation is principally of volcanic rocks, with schists and tertiary limestone; and an early physical connexion of the islands with New Zealand is indicated by their geology and biology.

The great plateau of Mexico is very largely of volcanic origin.

Its superstructure consists of igneous rocks of all descriptions with which the original valleys between its marginal ranges have been filled by volcanic action.

This part of Mexico is highly volcanic in character, the transverse ridge just described having a large number of extinct volcanoes and at least three (Colima, Jorullo and Ceboruco) that are either active or semi-active.

Lying off San Blas in the broad entrance to the Gulf are the Tres Marias, and directly west of Colima, to which it belongs, is the scattered volcanic group of Revillagigedo.

But by far the most important of the Tertiary rocks are the volcanic lavas, agglomerates and ashes, which cover so much of the country.

Copper was known to them, and it is possible that they knew how to make cutting instruments from it, but they generally used stone axes, hammers and picks, and their most dangerous weapon was a war-club into which chips of volcanic glass were set.

Streams of rainwater, formed by condensation of exhaled steam often mingled with volcanic ashes so as to produce mud, are known as lava d'acqua, whilst the streams of molten matter are called lava di fuoco.

The term lava is applied by geologists to all matter of volcanic origin, which is, or has been, in a molten state.

The lava is emitted from the volcanic vent at a high temperature, but on exposure to the air it rapidly consolidates superficially, forming a crust which in many cases is soon broken up by the continued flow of the subjacent liquid lava, so that the surface becomes rugged with clinkers.

Guatemala is naturally divided into five regions - the lowlands of the Pacific coast, the volcanic mountains of the Sierra Madre, the so-called plateaus immediately north of these, the mountains of the Atlantic versant and the plain of Peten.

The direction of the great volcanic cones, which rise in an irregular line above it, is not identical with the main axis of the Sierra itself, except near the Mexican frontier, but has a more southerly trend, especially towards Salvador; here the base of many of the igneous peaks rests among the southern foothills of the range.

It is, however, impossible to subdivide the Sierra Madre into a northern and a volcanic chain; for the volcanoes are isolated by stretches of comparatively low countr y; at least thirteen considerable streams flow down between them, from the main watershed to the sea.

Viewed from the coast, the volcanic cones seem to rise directly from the central heights of the Sierra Madre, above which they tower; but in reality their bases are, as a rule, farther south.

Fruits, grain and medicinal plants are obtained in great abundance, especially where the soil is largely of volcanic origin, as in the Altos and Sierra Madre.

Volcanic action has been restricted in the Rocky Mountains proper.

It is in association with this field of extinct volcanic activity that a remarkable group of geysers and hot springs has been developed, from which the Yellowstone river, a branch of the Missouri, flows northeastward, and the Snake river, a branch of the Columbia, flows south-westward.

Volcanic features occur in abundance in the Plateau province.

Mt Taylor in western New Mexico is of similar age, but here dissection seems to have advanced farther, probably because of the weaker nature of the underlying rocks, with the result of removing the smaller cones and exposing many lava conduits or pipes in the form of volcanic necks or buttes.

The lava plains of the Columbia basin are among the most extensive volcanic outpourings in the world.

The earlier supposition that these vast lava flows came chiefly from fissure eruptions has been made doubtful by the later discovery of flat-sloping volcanic cones from which much lava seems to have been poured out in a very liquid state.

They consist, in most parts of the country, of unconsolidated sediments, consisting of gravel, sand, clay, &c., together with large quantities of tuff, volcanic agglomerate, &c. Some of the sedimentary formations are of marine, some of brackish water, and some of terrestrial origin.

This was the result of several conditions, among them the recent development, through warping and faulting and volcanic extrusion, of high lands with more or less considerable slopes.

The Fort Union stage, when the deposition was widespread about the eastern base of the northern part of the Rocky Mountains, and at some points in Colorado (Telluride formation) and New Mexico (Puerco beds), where volcanic ejecta entered largely into the formation.

It contains much volcanic material, and great bodies of siliceous shale, locally estimated at 4000 ft.

The amount of volcanic material, consisting of both pyroclastic material and lava flows, is great.

Volcanic activity and faulting on a large scale attended the deforijiation of the closing stages of the Miocene.

Igneous rocks, whether lava flows or pyroclastic ejections, are less important in the Quaternary than in the Tertiary, though volcanic activity is known to have continued into the Quaternary.

The lode was an ore channel of great dimensions included within volcanic rocks of Tertiary age, themselves broken through pre-existing strata of Triassic age, and exhibited some of the features of a fissure vein, combined in part with those of a contact deposit and in part with those of a segregated vein.

This bed of volcanic rock may be followed northward in the cliffs, and it may be noticed that it thickens considerably in that direction.

Evidences of volcanic action are also traceable in the legends connected with Heracles at Aedepsus and Cenaeum, which here, as at Lemnos and elsewhere in Greece, have that origin.

On the other hand, the lightning is not associated with him in literature or cult, and his connexion with volcanic fires is so close as to suggest that he was originally a volcano-god.

The Lemnian version is due to the prominence of his cult at Lemnos in very early times; and his fall into the sea may have been suggested by volcanic activity in Mediterranean islands, as at Lipara, and Thera.

In Sicily, however, the volcanic nature of the god is prominent in his cult at Etna, as well as in the neighbouring Liparaean isles.

The island is entirely volcanic, and the soil is finely disintegrated lava.

The name "Kurile" is derived from the Russian kurit (to smoke), in allusion to the active volcanic character of the group. The dense fogs that envelop these islands, and the violence of the currents in their vicinity, have greatly hindered exploration, so that little is known of their physiography.

Near its southern extremity it rises into a fine dome-shaped volcanic mountain, Kartola (Karthala), which is over 8500 ft.

All the large and some of the small islands appear to be composed of ancient volcanic rock, with an incrustation of coral limestone showing here and there along the coast.

Vordate, Molu and south-eastern Yamdena have a maximum height of 820 ft.; the rest are low and flat, except Laibobar, apparently a volcanic islet on the west, which has an extinct crater 2000 ft.

All the islands are of volcanic origin, and have been built up by the eruptive process from a base about 15,000 ft.

With the exception of the coral and a small amount of calcareous sandstone, the rocks are entirely volcanic and range from basalt to trachyte, but are mainly basalt.

Its surface consists mainly of the gentle slopes of five volcanic mountains which have encroached much upon one another by their eruptions.

According to an account of the natives, a violent eruption of Kilauea occurred in 1789, or about that time, and deposits of volcanic sand, large stones, sponge-like scoria (pumice) and ashes for miles around are evidence of such an eruption.

The free acid is found native in certain volcanic districts such as Tuscany, the Lipari Islands and Nevada, issuing mixed with steam from fissures in the ground; it is also found as a constituent of many minerals (borax, boracite, boronatrocalcite and colemanite).

Eruptive rocks of supposed Cretaceous age are met with in these outer islands, but Tertiary and recent volcanic lavas are confined to the innermost arc. Halmahera lies outside these arcs.

Fruit is good and abundant as the rich volcanic soil is well watered from the town springs.

This tale, as well as the name Aethaleia, sometimes applied to it, points to its volcanic character.

All volcanic action is now extinct.

Inside the ramparts the town lies rather cramped, with narrow, crooked streets, badly drained and dirty; the houses are generally built of dark grey volcanic stone with flat roofs, the general aspect, owing to the absence of trees, being somewhat gloomy.

It differs considerably from the other members of the Sundanese group both in the direction of its main axis and in the prevalence of old rocks and slighter volcanic character.

It comes, however, within the great volcanic zone which stretches from the north of Sumatra, through Java and the other Sundanese islands, round to Amboyna, Tidore, Ternate, Halmahera and the Philippines.

There appear to be volcanic centres in both the east and the west of the island, and the surface is everywhere extremely rugged, with ridges from 4000 to 8000 ft.

Volcanic rocks are also present but they are not so extensively developed as in the islands of the Javan arc. The Permian beds consist chiefly of limestone and contain numerous fossils similar to those of the middle and upper divisions of the Productus limestone of northern India and the Artinsk stage of the Urals.

Fragments of Jurassic rock have been found amongst the volcanic material on the island of Rotti, but they have not yet been discovered in situ.

Subsequently, in the Tertiary period, there were two enormous outpourings of volcanic material - first andesitic lava, and later, after a long interval of quiet, rhyolitic - which nearly half filled the basin, converted it into a plateau and broke up the mountain rim.

Two centres of volcanic activity were Mt.

It is cut in the volcanic plateau, and its ragged broken walls, which are inclined at very steep angles, are of a richness of colouring that almost defies description, a colouring that is produced by the action of the thermal springs, at the base of the canyon, upon the mineral pigments in the lava.

After the destruction of one forest by volcanic eruptions another grew over it; it, too, was buried under volcanic material, and the process was repeated several times.

Triassic Permian Plutonic Rocks Volcanic Rocks West of a line which runs from Lake Constance to Lago Maggiore the zones already described do not continue with the same simplicity.

In intimate relationship with the mountain-building orogenic crustal movements was the prevalence of volcanic activity during the earlier part of this period.

In the Lower Carboniferous rocks of Scotland intercalated volcanic rocks are strikingly abundant, and now form an important feature in the geology of the southern portion of that country.

In North America, the principal region of volcanic activity lay in the west; great thicknesses of igneous rocks occur in the Lower Carboniferous rocks of British Columbia, and from the middle of the period until near its close volcanoes were active from Alaska to California.

On the south and south-east the valley is bounded by two volcanoes, Lubuk Raja and Si Buwal Buwali, whence were derived the volcanic tuffs of the valley and of the plateau of Sipirok, with their lakes, which are drained by the Batang Toru and its affluents.

Arsenic, saltpetre, alum, naphtha and sulphur may be collected in the volcanic districts.

On the left bank this clay has been reached at a lower level, at the foot of the Pincian Hill, while in the Campagna it has been found to extend below the later volcanic formations.

In the second period volcanic activity occurred at the bottom of the Pliocene sea, and the tufa, which extends over the whole Campagna to a thickness of 300 ft.

In the third, after the Campagna, by a great general uplift, had become a land surface, volcanic energy found an outlet in comparatively few large craters, which emitted streams of hard lava as well as fragmentary materials, the latter forming sperone (lapis Gabinus) and peperino (lapis Albanus), while upon one of the former, which runs from the Alban Hills to within 2 m.

The volcanic materials available in Rome and its neighbourhood were especially useful in building.

Between the volcanic tract of the Campagna and the sea there is a broad strip of sandy plain, evidently formed merely by the accumulation of sand from the sea, and constituting a barren tract, still covered almost entirely with wood as it was in ancient times, except for the almost uninterrupted line of villas along the ancient coastline, which is now marked by a line of sandhills, some 2 m.

The mineral products of the district also include lignite, copper, manganese, vitriol, lime, gypsum, volcanic stones (used for millstones) and slates.

St Kilda is probably the core of a Tertiary volcano, but, besides volcanic rocks, contains hills of sandstone in which the stratification is distinct.

At Ruby Hill near Bingara they were found in a breccia filling a volcanic pipe.

There has been much contirversy concerning the nature and origin of the blue ground itself; and even granted that (as is generally believed) the blue ground is a much serpentinized volcanic breccia consisting originally of an olivine-bronzite-biotite rock (the so-called kimberlite), it contains so many rounded and angular fragments of various rocks and minerals that it is difficult to say which of them may have belonged to the original rock, and whether any were formed in situ, or were brought upfrom below as inclusions.

The district on each side of the lake has a number of hot springs, at least one of which is beneath the sea itself, and has always shown indications of volcanic and other subterranean disturbances.

In the north-east, between the Lot and its tributary the Truyere, lies the lonely pastoral plateau of the Viadene, dominated by the volcanic mountains of Aubrac, which form the north-eastern limit of the department and include its highest summit (4760 ft.).

Vesuvius (q.v.), the volcanic forces of which had been slumbering for unknown ages, suddenly burst into violent eruption, which, while it carried devastation all around the beautiful gulf, buried the two cities of Herculaneum and Pompeii under dense beds of cinders and ashes.

No good building stone was at hand; and the public as well as private edifices were constructed either of volcanic tufa, or lava, or Sarno limestone, or brick (the latter only used for the corners of walls).

The portion of the portico surrounding the forum which was in the process of rebuilding at the time when the city was destroyed was constructed of this material, while the earlier portions, as well as the principal temples that adjoined it, were composed in the ordinary manner of volcanic tufa.

Chalcedony occurs as a secondary mineral in volcanic rocks, representing usually the silica set free by the decomposition of various silicates, and deposited in cracks, forming veins, or in vesicular hollows, forming amygdales.

In the north-west the Upper Guinea mountains send their eastern spurs across the boundary, and from a volcanic rift, which runs southwest to north-east, the Cameroon peak towers up, its summit 13,370 ft.

The materials are quartz crystal, basalt, porphyry, syenite, granite, volcanic ash, various metamorphics, serpentine, slate, dolomite marble, alabaster, many colored marbles, saccharine marble, grey and white limestones.

The islands are volcanic, the main geological formation being Tertiary or Jurassic basalt, which occasionally protrudes through the ice-cap in high isolated blocks near the shore.

That volcanic influences are still present may be inferred from the circumstance that the snow cap on Popocatepetl disappeared just before the remarkable series of earthquakes that shook the whole of central Mexico on the 30th and 31st of July 1909.

Near Hasbeya are bitumen pits let by the government; and to the north, at the source of the Hasbani, the ground is volcanic. Some travellers have attempted to identify Hasbeya with the biblical Baal-Gad or Baal-Hermon.

The northern part of the mountain chain of the northern peninsula is volcanic, its volcanoes continuing the line of those of Makian, Ternate and Tidore.

His interest in mineralogy led him to study the geology of volcanic regions, and he made frequent visits to the Eifel with a view to the discovery of a theory of volcanic action.

Extensive volcanic outbursts occurred in this region during the Tertiary period.

In the south, the older beds disappear and the whole chain is formed chiefly of Cretaceous beds, though Eocene and probably Jurassic rocks are Medit Er R Anean Plutonic Rocks Volcanic Rocks o Active Volcanoes present.

They are mostly of volcanic origin, and include pumice, tufa, santorin earth, trass and pozzuolana itself.

Generally speaking, they are only of local importance, their cheapness depending largely on the nearness and abundance of some suitable volcanic deposit of the trass or tufa class.

No traces of recent volcanic action exist in Lycia.

The lowest of these younger rocks are the various sedimentary and volcanic members of the Old Red Sandstone.

The volcanic rocks of this division form ranges of hills in the Lowlands, such as the Pentlands, Ochils and Sidlaws.

The lavas are usually porphyrites, which occur in sheets, with intercalated bands of volcanic tuff that are sometimes strongly felsitic. One of the vents by which such materials were ejected occurs in the Braid Hills on the south side of Edinburgh.

There was great volcanic activity during the deposition of the Calciferous Sandstone, Carboniferous Limestone and Millstone Grit series.

The two leading types of volcanic areas are the plateaus, in which sheets of porphyrites, basalts and even trachytes were emitted, sometimes with wide discharge of volcanic ashes, and the puys, or isolated vents, or scattered groups of vents, which discharged comparatively a small amount of lava and ashes.

Most of the hills and crags in the Carboniferous area are volcanic, and many of them - such as the castle rocks of Edinburgh and Stirling, Binny Craig in Linlithgowshire, North Berwick Law and the Bass Rock - mark the sites of actual events of eruption.

One of the most interesting features of the Scottish development of the Permian system is the occurrence of intercalated bands of contemporaneously erupted volcanic rocks in the Carron, Nithsdale and Ayrshire.

The volcanic episode to which these plateaus owe their origin was one of the most important in the geological history of Great Britain.

That the volcanic period was a prolonged one is shown by the great denudation of the plateaus before the last eruptions took place.

A remarkable feature in the volcanic phenomena was the disruption of the basaltic plateaus by large bosses of gabbro and of various granitoid rocks.

The northern chain is of volcanic formation, and contains the peak of Lombok (ii,81o ft.), one of the highest volcanoes in the Malay Archipelago.

Between the two chains is a broad valley or terrace with a range of low volcanic hills.

They lie within a coral barrier reef, and in the south the islands are of coral, but in the north of volcanic rocks.

After each disaster the people returned, the advantage of the rich volcanic land overcoming apprehensions of danger.

Their colour is a brown, lighter or darker generally according to the amount of their exposure to the sun - being darker on some of the atolls where the people spend much time in fishing, and among fishermen on the volcanic islands, and lighter among women, chiefs and others less exposed than the bulk of the people.

The rocks are largely volcanic, the stratification being complex.

The island, which is volcanic, is bare and rocky throughout; the hills, of which the highest rises to about Boo ft., command magnificent views of the neighbouring sea and islands.

The volcanic character of the region is likewise responsible for large areas of barren surfaces.

The geological structure of the mountain furnishes no evidence of volcanic activity.

In addition to the climatic changes due to altitude, there are others caused by local arid conditions, by volcanic influences and by the influence of mountain ranges on the temperature and rainfall of certain districts.

Mr Whymper's explanation of the phenomenon is that the fish are scattered over the land by the sudden overflow during volcanic eruptions of the rivers and lakes which they inhabit.

Of the numerous islands that dot the Gulf many are partly at least of volcanic origin, notably Qishm and Ormuz.

Eastern Moquegua is volcanic, and is broken by the high range that forms the western rim of the Titicaca basin.

The island is of volcanic origin, a fragment of an ancient stream of lava.

Teneriffe and Gomera, the only members of the principal group which have a common base, may be regarded as the twin peaks of one great volcanic mass.

Ever since the researches of Leopold von Buch the Canary Islands have been classical ground to the student of volcanic action.

In common with the other West African islands they are of volcanic origin.

Owing to the richness of the volcanic soil, agriculture in the Canaries is usually very profitable.

It is a large volcanic region, entirely covered with lava and other igneous rocks.

Through these, again, pierce other granites in dikes or lava flows, and overlying the whole are limestones of Cretaceous and Tertiary age, themselves cut through by later volcanic eruptions.

In early and middle Tertiary times, when the Indian peninsula was an island, and the sea which stretched into Europe washed the base of the Himalayan hills, Sokotra was in great part submerged and the great mass of limestone was deposited; but its higher peaks were still above water, and formed an island, peopled mainly by African species - the plants being the fragmentary remains of the old African flora - but with an admixture of eastern and other Asian forms. Thereafter it gradually rose, undergoing violent volcanic disturbance."

The end of the Cretaceous period saw the beginning of a series of great earth movements ushered in by volcanic eruptions on a scale such as the earth has never since witnessed, which resulted in the upheaval of the Himalayas by a process of crushing and folding of the sedimentary rocks till marine fossils were forced to an altitude of 20,000 ft.

Although volcanic cones are known both in Persia and in Baluchistan, none have yet been described in Afghanistan itself.

There is, however, ample evidence that at several distinct geological periods the region has been the seat of great volcanic activity.

Griesbach, basic volcanic rocks are interbedded with the lowest part of the plant-bearing series, and enormous outbursts took place during the Neocomian period.

The great volcanic outbursts which produced this trap commenced in the Cretaceous period and lasted on into the Eocene period.

South of the Kwanza is the volcanic mountain Caculo-Cabaza (3300 ft.).

The island is of volcanic origin, but has ceased to show signs of volcanic activity.

The greater part of the surface is composed of a volcanic breccia, with here and there lava-streams exposed in ravines, and sometimes on the surface.

The Afar country is part of the East African rift-valley, and in the southern parts of the valley its surface is diversified by ranges of hills, frequently volcanic, and by lakes.

Italiana of Florence for 1906-1908, dealing with the volcanic regions.

The islands are mainly of volcanic origin, and their surface is much broken by hills, isolated volcanoes and mountain ranges, trending north and south, north-west and southeast, or north-east and south-west.

In Leyte there are several isolated volcanic cones, two of which, in the north part, exceed 4000 ft.

There were border wars with rebellious savage tribes, attacks made by Chinese pirates seeking plunder or refuge, volcanic eruptions, earthquakes, tornadoes and the periodical visits of marauders from the southern islands.

Medina lies between two volcanic hills, called harra.

Recent eruptive and volcanic rocks are met with in the interior of Korea and also in the island of Quelpart.

Both Great and Little Ararat consist entirely of volcanic rocks, chiefly andesites and pyroxene andesites, with some obsidian.

The earthquake and fall of rock which destroyed the village of Arghuri in 1840 may have been caused by a volcanic explosion, but the evidence is unsatisfactory.

Where the volcanic formations were spread uniformly over the flanks of the mountains, the contrast between the canyons and the plain-like region of gentle slope in which they have been excavated is especially marked and characteristic. The eastern slope is very precipitous, due to a great fault which drops the rocks of the Great Basin region abruptly downward several thousand feet.

Volcanic action has likewise left abundant traces, especially in the northern half of the range, whereas the evidences of glacial action are most perfect (though not most abundant) in the south.

The eastern half of this area is covered chiefly with volcanic plains, very dry and barren, lying between precipitous, although not very lofty, ranges; the western half is magnificently timbered, and toward the coast excessively wet.

The plains of the north-east counties are volcanic, and those of the south-east sandy.

Iriga, a volcanic peak reaching a height of 4092 ft.

On the east side in North Glen Sannox Burn, they are associated with cherts, grits and dark schists with pillowy lavas, tuffs and agglomerates which, on lithological grounds, have been regarded as probably of the same age as the Arenig cherts and volcanic rocks in the south of Scotland.

Contemporaneous volcanic rocks, belonging to three stages of the Carboniferous formation, occur in Arran.

The second is represented by a thin lava, associated with the Upper Limestone group of the Carboniferous Limestone series, and the highest is found in Ben Lister Glen intercalated with the Upper Carboniferous strata, and may be the equivalent of the volcanic series which, in Ayrshire, occupies the position of the Millstone Grit.

The former extension of Rhaetic, Liassic and Cretaceous formations in the island is indicated by the presence of fragments of these strata in a large volcanic vent on the plateau, on the south side of the road leading from Brodick to Shiskine.

The fossils from the Rhaetic beds belong to the Avicula contorta zone, those from the Lias to the Ammonites angulatus zone, while the blocks of limestone with chert contain Inoceramus, Cretaceous foraminifera and other organisms. The materials yielding these fossils are embedded in a course volcanic agglomerate which gives rise to crags and is pierced by acid and basic igneous ricks.

Another granite area appears on the south side of the road between Brodick and Shiskine, where it is associated with granophyre and quartz-diorite and traverses the volcanic vent of post-Cretaceous or Tertiary age already described.

In the region between the Northern and Southern Rockies, the plains are interrupted by minor Mountain groups, volcanic buttes and lava flows, among which the Leucite Hills and Pilot Butte are prominent examples.

In 1883 Sunda Strait was the scene of the most terrific results of the eruption of Krakatoa, a volcanic island further west in the strait.

Excluding some of alluvial formation at the mouths of many of the rivers, and others along the shore which owe their existence to volcanic upheaval, the principal islands are Banguey and Balambangan at the northern extremity, Labuan, a British colony off the west coast of the territory of North Borneo, and the Karimata Islands off the south-west coast.