The margin of this new lake, acting upon the detrital matter, would form the second road.
On the Parallel Roads of Lochaber; with Remarks on the Change of Relative Levels of Sea and Land in Scotland, and on the Detrital Deposits in that Country.
Taking all the circumstances into account, you may, I think, with safety dismiss the detrital barrier as incompetent to account for the present condition of Glen Gluoy and Glen Roy.
It is also noteworthy that no detrital rock, whether agglomerate, tuff, or tuff-clay came under my observation.
It is however of detrital origin, and is composed in mass of minute fragments of a basic, sometimes vacuolar, glass in great part converted into palagonite; whilst there are a number of broken crystals of olivine and plagioclase.
In the absence or rarity of detrital rocks this part of the range resembles the adjacent mountain of Seatura.
The blocks of limestone included in the volcanic agglomerates distinguish the Lau detrital rocks from those of Vanua Levu.
There protrudes through these detrital rocks at the top of the hill a broad dyke-like mass of the same basaltic andesite that forms the agglomerate around; and the structure of the hill is thus displayed as that of an old volcanic neck.
Placers are detrital or fragmental sediments containing the ore in mechanical fragments, which are derived from the erosion and transportation of solid-rock veins or lodes, sometimes called the "mother lode.
Near the surface the pisolites are sometimes loosened by weathering, yielding a gravel ore, and some of the material has been transported a short distance to form detritalores interstratified with sands and gravels.
European deposits maintained the characters already indicated; limestones (not chalk) prevailed, except in certain Alpine and Carpathian tracts where detrital sandstones were being laid down.
Traced eastward into north Germany, Thuringia and Silesia, the limestones pass into the detrital culm formations, which owe their existence to a southern uplifted massif, the complement of the synclines already mentioned.
It does not go to increase the great body of detrital deposits.
The river supply of detrital sediment has not been very extensively investigated, although the quantities involved may be found with comparative ease and accuracy.
The fact is, the deposited detrital sediments around the continents occupy an area small when contrasted with the vast stretches of the land.
The transport by denudation of detrital and dissolved matter from the land to the ocean has had a most important influence on the events of geological history.
The chemical composition of the detrital sediments which are spread over 41 the continents and which build up the mountains, differs on the average very considerably from that of the igneous rocks.
In such scenes of desolation and destruction, detrital sediments are actively being generated.
And, again, the conditions of aeration and circulation which largely promote chemical and solvent denudation in the soils are relatively limited and ineffective in the detrital oceanic deposits.
The summation of the amounts of dissolved and detrital materials which denudation has brought into the ocean during the long denudative history of the Earth, as we might anticipate, reveals quantities of almost unrealisable greatness.
We have now considered the source of the detrital sediments, as well as of the dissolved matter which has given to the ocean, in the course of geological time, its present gigantic load of salts.
Why does detrital matter remain suspended in the water of rivers?
The action of waves is another means by which detrital matter is furnished.
The Gulf Stream, and the Mozambique and other similar currents, must be wearing down the valleys through which they flow, to such an extent as to furnish an immense amount of detrital matter for the formation of new rocks.
The detrital matter obtained in these several ways is swept away by running water.
If the current of a main river be not powerful enough to sweep away detrital matter brought down by a lateral stream, a dam is formed causing a lake.
These outgoing streams, however, being very pure and clear, all detrital matter having been deposited in the lake, have less eroding power than inflowing streams.
With the exception of the detrital sediments of the Bermuda Apron, the scoured crests and flanks of the larger seamounts, and the steeper scarps, the Bermuda Rise is covered preponderantly by pelagic sediments.
This is in sharp contrast to the surrounding abyssal plain and near-by continental rise, where cores reveal frequent alterations of detrital and pelagic sediments (Pl.
The sides also became less vertical, and there was an accumulation ofdetrital fragments about their bases.
The effect of allowing the water to penetrate is not only to diminish the superficial wearing, but to maintain the process of subsoil and bed-rock decay by which the detrital covering is naturally renewed.
He should see that his work brings two risks; he may impoverish the accumulation ofdetrital material by taking out the plant food more rapidly than it is prepared for use.
In almost every large area the process of erosion naturally leaves quantities of rock, either in the form of detached columns or as detrital accumulations deposited on steep slopes.
The study of any considerable river basin enables us to trace the more important steps which lead to the destructure and renovation of the earth's detrital coating.
Not only does the land life maintain itself on the soil, and give much to the sea, but it serves in various ways to protect this detrital coating from too rapid destruction, and to improve its quality.
Here the natives collect dust by laborious washings of detrital sand.
During the emergence of the first dry land, large quantities of detrital matter must have been deposited in the waters, and in part elevated into land.
