In the Wenlock beds of the west of the Dingle promontory there are contemporaneous tuffs and lavas.
Contemporaneous volcanic action is recorded by tuffsand lavas south-east of Limerick and north of Philipstown.
The solid nucleus of the reef, where the black rock is now found, withstands the movements of the sea; while the surrounding loose tuffs are cut away to a somewhat lower level.
The dikes are for the most part vertical, but sometimes they run in a tortuous course through the tuffs and breccias, as represented in fig.
It will be observed in the above section that two of the brown, half-consolidated tuffs are filled with small pisolitic globules.
The Herculanean tuffs containing the rolls of papyrus, of which the characters are still legible, have, as was before remarked, been for ages covered by lava.
In many of the dikes which intersect the tuffs and lavas of Etna, there is scarcely any perceptible alteration effected by heat on the edges of the horizontal beds, in contact with the vertical and more crystalline mass.
The high inclination of some of the beds, and the firm union of the particles even where there is evidently no cement, is another striking feature in the volcanictuffs and breccias, which seems at first not very easy of explanation.
Interbedded lavas and tuffs are found in the island of Hoy.
Interbedded volcanic rocks, andesites, dacites, diabases, with agglomerates and tuffs constitute an important feature, and attain a thickness of 6000 ft.
In Devonshire diabases andtuffs are found in the middle division.
On the Pacific coast metamorphism of the rocks is common, and lava-flows and tuffs occur in them.
The middle division has diabases and tuffs at the top with Tentaculite and Nereite shales and limestones below.
Felsitic lavas and tuffs occur in the Middle Devonian of Australia.
Ancient tuffs are known by the fragmental character of their volcanic material, even though they have been altered to firm rock.
The mountain basin of the Yellowstone Park was filled to a depth of several thousand feet with tuffs and lavas, the oldest dating as far back as the beginning of the Tertiary.
The materials of which tuffs are composed are easily recognized as volcanic in their origin.
Some remains of land animals and plants may be found imbedded to tell that the beds were laid in open air; while the remains of marine organisms would prove as surely that the tuffs were deposited in the sea.
The absence of tuffs and lavas among the Carboniferous strata of North America shows that here volcanic action was singularly wanting during the entire period.
The remainder of the base of the ancient mountain is made of rudely beddedtuffs and volcanic breccia, with occasional flows of lava, some of the fragments of the breccia measuring as much as twenty feet in diameter.
But even when little or no lime is present, there is a great tendency in the materials of ordinary tuffsto cohere together.
The tuffs now alluded to are not exclusively marine, but include, in some places, freshwater shells; in others, the bones of terrestrial quadrupeds.
In the lowest part of this division, beds of pure marl alternate with compact fissile tuff, resembling some of the subaqueous tuffs of Italy and Sicily called peperinos.
B] The peperinos thus distinguished are usually brown, and the tuffsgrey or white.
Hence they differ from the volcanic rocks, not only by their more crystalline texture, but also by the absence of tuffs and breccias, which are the products of eruptions at the earth's surface, or beneath seas of inconsiderable depth.
These tuffs and marls are highly inclined, and traversed by a thick vein of basalt, which, as it rises in the hill, divides into two branches.
These tuffs occur on the flanks of the Wrekin and Caer Caradoc, and contain Silurian fossils, such as casts of encrinites, trilobites, and mollusca.
They project in relief several inches, or sometimes feet, from the face of the cliff, being extremely compact, and less destructible than the intersected tuffs and porous lavas.
The Boleo copper deposits of Lower California occur in volcanic tuffs and associated conglomerates of Tertiary age.
The contemporaneous volcanic rocks intercalated in this Upper Old Red consist of feldspathic lavas, or feldstones, with associated tuffs or ashy beds.
These tuffs of the southern shores of the Grand Canary, containing the Upper Miocene shells, appear to be about the same age as the most ancient volcanic rocks of the island, composed of slaty diabase, phonolite, and trachyte.
The largest number of fossils have been collected from the tuffs and conglomerates and some beds of limestone in the island of Baixo, off the southern extremity of Porto Santo.
In the volcanic tuffs of this age are found not only fragments of limestone, shale, flinty slate, and sandstone, but also pieces of coal.
Tuffs often contain volcanic bombs,--balls of lava which took shape while whirling in the air, and solidified before falling to the ground.
Coarse tuffs of angular fragments are called volcanic breccia, and when the fragments have been rounded and sorted by water the rock is termed a volcanic conglomerate.
Porphyritic tuffs and massive limestone compose the western chain of the Andes above Lima, while in the Oroya Valley we find carbonaceous sandstones.
Some of the tuffs may be of the Jurassic age, though the Cretaceous period is also largely represented.
Farther north nearly the whole of the depression is filled with lavas, tuffs and agglomerates, derived from the Tertiary and recent volcanoes which form the most striking feature of the Andes of Ecuador.
In this group there may also have been placed metamorphosed acidtuffs and a certain number of adinoles (shales, contact altered by intrusions of diabase).
The lower beds generally consist of fine-grained, slightly consolidated tuffs (Some of this peperino, or tuff, is sufficiently hard not to be broken by the greatest force of the fingers.
Siliceous deposits seem to be very general, if not of universal occurrence, in partially decomposed trachytic tuffs (Beudant "Voyage Min.
These feldspathic lavas and tuffs are the uppermost or those last erupted; innumerable dikes, however, and great masses of molten rock, have subsequently been injected into them.
From the Cambrian period all through Palaeozoic times there rose at intervals in that country a succession of volcanic centres from some of which thousands of feet of lavas and tuffs were discharged.
The acid and basic tuffs in the vicinity of Tawaki and Thawaro are, as I imagine, largely derived from marine degradation.
It is evident that through the alteration of the palagonitic constituents, which were probably more frequent when the tuffs were deposited, the structure of the matrix is somewhat disguised.
The tuffsand clays underlying the agglomerates are, as already remarked, much disturbed in places.
The early stages of alteration are well displayed in some of the tuffs formed mainly of basic vacuolar glass, the submarine character of which is often indicated by a few tests of foraminifera.
In ascending from Koro-vatu on the west side basic agglomerates and agglomerate-tuffs were found exposed as far as half-way up.
If reefs had been formed along those ancient coasts, or on the original shoals, they would have been in some cases preserved, as in the case of the foraminiferous tuffs and clays, by a covering of volcanic agglomerate.
They contain at times subangular fragments of more basic rocks; and are true tuffs in the sense that although perhaps deposited on a sea-bottom they represent the ejected materials of a subaerial vent.
The filling up of a fissure in a mass of tuff-breccia by palagonite-tuffs and agglomerates probably occurred during the submergence, the original dyke-rock having been removed by marine erosion.
In the cores of the arches of Arenig cherts there are diabase lavas, tuffs and agglomerates which are typically represented on Bail Hill E.
They are built up of a great variety of ancient lavas and fragmental tuffs or "ashes," which are inclined in many different directions.
The beds are occasionally separated by layers of sandstone, grit, and conglomerate; but such beds are rare, and true tuffs are rarer still.
Sao Vicente, and again at about the same height in Porto Santo, there have been found fragments of limestone accompanied by tuffs containing marine shells and echinoderms of the Miocene Tertiary epoch.
Moreover, great alterations and dislocations had taken place in the rocks of various localities before other lavas and tuffs had been thrown upon them.
An adjacent islet is formed of tuffs and calcareous rock, indicating a submarine origin, upon which supramarine lavas have been poured.
Basic lavas, with andesites, trachytes, tuffs and agglomerates are the most common Scottish rocks of this period.
Porphyrites andtuffs are known in the French Carboniferous.
Rames, a very competent geologist, were interstratified with tuffs and lavas of these older volcanoes, and no doubt as to their geological age was raised by the Congress of French archaeologists to whom they were submitted.
The great antiquity of those gravels and volcanic tuffs is further confirmed by the changes in the flora and fauna which are proved to have occurred.
Kadesh and the epic poem of Pentaur must have been known to the generation before the Exodus as signal events.
The formation of the jaws and teeth affords another important test.
In fact, we have the authority of Darwin himself, as quoted in the beginning of this chapter, for saying that this would be quite consistent with his view of the origin of species.
They must have been close to the scene of the final campaigns, the siege of Avaris, and the expulsion of the Hyksos.
If the sojourn in Egypt really lasted for 430 years, it must have embraced many of the greatest events in Egyptian history.
It chiefly consists of stratified volcanic tuffs rich in coal, lignite, fossilized plants and an invertebrate fauna.
The foundation of the island is formed by a series of stratified shales and conglomerates, with tuffs and other volcanic rocks and occasional bands of marine limestone.
The latter lavas and tuffs may have originated from smaller and less important cones, now destroyed by erosion.
The beds of fragmental material are of the nature of flow breccias and of coarse agglomerates on the higher slopes, while tuffs occur at a greater distance from the center of eruption.
The above list will hopefully give you a few useful examples demonstrating the appropriate usage of "tuffs" in a variety of sentences. We hope that you will now be able to make sentences using this word.
