Chapter XI: The Geologic Functions of Life (2)

=The contribution of the Protozoa.=—The Protozoa are related to the animal kingdom much as the Thallophytes are to the vegetable, and the two bear a close structural resemblance to one another. So near, indeed, do the Protozoa and the Thallophytes approach one another in their minuteness and simplicity, that the place of not a few organisms is in doubt, and the two kingdoms, in general so different, seem here to blend in the group Flagellata. The Protozoa are usually very minute one-celled organisms with very little differentiation of tissue or organs. Of the four classes of Protozoa, only one, the Rhizopoda, is found in the fossil state. The rhizopods secrete silicious skeletons, and calcareous, silicious, and chitinous tests of a great variety of forms, and this gives them geologic importance. The deep-sea oozes and the chalk deposits are their best-known contributions at present. They have probably played a more important rôle in the formation of ordinary limestones and silicious silts than can be demonstrated, because of the delicacy of their relics and the ease with which these are pulverized by wave-action in the shallow seas, or changed by recrystallization or by concretionary aggregation. The globigerina oozes are formed largely from the calcareous shells of Foraminifera (Fig. 351), one of the orders of rhizopods, among which the genus Globigerina is a leading form. Those forms which make the deep-sea oozes live, not on the bottom, but near the surface of the open sea, and on the death of the organisms, the shells, tests, and skeletons sink to the bottom. Chalk is formed in a similar way from calcareous Foraminifera, but not necessarily in very deep water. Foraminifera live in shallow water as well as in the open sea, and in this case they sometimes creep on the bottom or are attached to algæ, but their deposits in shallow water are usually much obscured by other kinds of deposition and by destructive action. Some of the foraminiferal shells are divided into chambers and assume various spiral forms, of which the _Nummulites_, named from their resemblance to coins, are notable examples. These formed an important part of the nummulitic limestone of the Eocene period.

The radiolarian ooze is characterized by the silicious tests of various members of the silica-bearing order, Radiolaria. The “Barbadoes earth” and “Tripoli” are notable deposits of fossil radiolarians.

=The contribution of the Cœlenterata.=—The Cœlenterata embrace the sponges, the coral polyps (Anthozoa), and the hydroids and medusæ (Hydrozoa). The contribution of coral polyps to the formation of limestone is most important, and is too familiar to require elaboration here. The corals range throughout nearly the whole fossiliferous series, and their development will be followed and illustrated in the historical chapters.

The sponges are widely represented by their spicules, and not uncommonly their aggregate form is preserved even in very ancient strata. Their contribution is largely silicious, but is partly calcareous. The hydroids and medusæ have left little trace of themselves in the rocks, although impressions supposed to represent medusæ are found in strata as early as the Cambrian. Certain coral-like forms, as the Millepores, Tubularia, and Stromatopora, are classed as Hydrozoa. The graptolites, delicate leaf-like floating forms, very serviceable in marking exact horizons on different continents because of their free distribution, are also classed here.

=The contribution of the Echinodermata.=—Under the echinoderms are grouped the crinoids (sea-lilies), cystoids, blastoids, ophiuroids (brittle stars), asteroids (starfishes), echinoids (sea-urchins), and holothuroids (sea-cucumbers). This is one of the marked groups of ancient as well as modern life, and its beautiful fossils grace every period in which life relics are well preserved. The cystoids and crinoids, and later the blastoids, were prominent in the Paleozoic ages, while the remaining forms were more conspicuous later, though early introduced. All divisions, except the holothuroids, whose softness prevented, have left a good record, as fossil records go. Their relics are chiefly calcareous, and they most abound in the limestones, some of which are largely made up of their remains, as the encrinital limestone (Fig. 349). They will be subjects of frequent comment and illustration in the historical chapters.

=The contribution of the Vermes.=—Most of the worms are ill adapted to fossilization and are not known in the fossil form. The segmental worms of the sea, the annelids, however, left some traces of themselves in tubes and borings and in tracks and sometimes by fossil jaws and teeth. They range from the earliest fossil-marked horizons onward, but seem to have always been an inferior group.

=The contribution of the Molluscoidea.=—This group includes the bryozoans, whose fossil products closely resemble the minute-celled corals, and the brachiopods, whose shells closely resemble those of the molluscs. Both are calcareous and make important contributions to the formation of limestone (Fig. 350). A few brachiopods secrete calcium phosphate instead of calcium carbonate. Both classes have a great geologic range and their fossils are valuable aids in identifying and correlating formations. Probably the brachiopods are more utilized for this purpose than any other single class. They are the symbol of conservatism and persistence, ranging from the Cambrian to the present time, and embracing some forms that have scarcely changed to the extent of generic difference in that time.

=The contribution of the Mollusca.=—The molluscs have also ranged from the earliest well-recorded times, and some divisions, as the pelecypods (lamellibranchs, embracing clams, oysters, etc.) and gastropods (snails, etc.), have undergone no very marked change beyond a rather ample and progressive development; but others, as the cephalopods (nautilus, squids, cuttlefish, etc.), mark out the progress of the ages by distinct and striking changes of form. Their shells are chiefly calcareous and they have contributed materially to the formation of limestone. Muddy and sandy bottoms are, however, more congenial to the pelecypods and gastropods than to the corals, crinoids, and many other limestone-forming types, and hence fossils of these molluscs frequently abound in shales and sandstones and give them a calcareous element. In sandstones, however, the calcareous matter is often dissolved out and only the casts of the shells remain. The molluscs will be much cited and illustrated in the historical chapters.

=The contribution of the Arthropoda.=—This group embraces the crustaceans, myriopods, spiders, and insects. The hard parts of their bodies are mainly horny or chitinous forms of organic matter, and hence their relics differ notably from the inorganic calcareous and silicious remains of most of the preceding forms. The Arthropoda did not at any time form a notable stratum of rock. Their geologic value lies chiefly in what they teach of the progress of life and its relations, and the aid they render in correlation and identification. In these respects the group is a notable one. It was represented in the early fossiliferous strata by the trilobites, one of the most interesting of all types of fossils. These were probably the most highly developed organisms of their times and give the clearest hints of the stage of psychological and sociological development that had been reached when first the record of life is opened to us. The record of the myriopods, spiders, and insects dates from the middle Paleozoic, and gives the first clear hints of animal life on the land.

=The contribution of the Vertebrata.=—In the vertebrates the dynamic or working organism may be said to reach its highest expression, unless it be in the flying insects, and their inorganic residue becomes relatively unimportant in rock formation. Although the greatest of all animal types in most respects, it has never formed more than trivial beds of rocks. There are occasional “bone beds,” but they are thin and limited in extent, and only partially formed of vertebrate matter. The geological importance of the vertebrates lies in the higher field of life evolution and in its mental accompaniment. Fishes excepted, the vertebrates are mainly land types, and have for their chief colleagues plants and insects. The other groups of animals are mainly, though not wholly, marine. The vertebrates have little place in the Paleozoic record, except near its close, but they dominate the Mesozoic and Cenozoic eras, and are conspicuously the master type to day.

III. THE ASSOCIATIONS AND ECOLOGICAL RELATIONS OF LIFE.

A. +The Basis of Floras and Faunas.+

Geologic interest is not confined to the kinds of plants and animals that have lived and the contributions they have made to the deposits, but embraces also their assemblage into floras and faunas, and the relations of these assemblages to the prevailing physiographic features. These assemblages and relationships are among the most suggestive factors of the earth’s evolution, and are the most instructive for purposes of comparison with human history, and for forecasting the future of man and of the whole biological kingdom. Moreover, floras and faunas, as such, are used in the correlation of formations, and in this application they give surer results than correlations by individual species. A particular species may live far beyond the usual period of a species, and if fossilized in one region in its early history and in another in its late history, the two formations might be referred erroneously to the same stage. This is far less likely to happen with a whole assemblage of forms. There is a similar liability to error in interpreting migrations on the basis of a single or a few species, for a single species or a few species may be transported by unusual or accidental means, so to speak, when there is no normal pathway for general migration, and when no systematic migration takes place. In most of the great questions that arise concerning the connections and disseverances of the continents, and concerning the unions and separations of the oceans, which are the fundamental causes of the migrations and of the isolations of plants and animals, typical floras and faunas are to be studied, rather than isolated species or sporadic forms. A brief sketch of the leading causes and consequences of these special assemblages of plants and animals may aid in appreciating the underlying significance of floras and faunas, and in interpreting their meaning as they are met in the study of the strata. A part of these grow out of the relations of the organisms to one another, and a part out of the relations of the organisms to their environment.

(1) _Assemblages Influenced by the Mutual Relations of Organisms._

(_a_) =Food relations.=—The relations of food-supply are among the most obvious reasons for assemblages. As animals are dependent directly or indirectly on plants for their food, they must gather where the plants grow, or in the currents in which the plant products are borne. Whatever determines an assemblage of plants also causes, or at least invites, an assemblage of animals. Whatever causes an assemblage of particular plants, invites an assemblage of the particular animals that use these plants. Animals that feed on plants are in turn preyed upon by other animals, and these in turn by others. A whole train of organisms may, therefore, be gathered into a region by the conditions that foster a certain kind of vegetation there. In interpreting the physical significance of such a train, it is obvious that the head of the train carries the fundamental meaning. The dependent creatures that follow the primary forms may be only incidentally, and perhaps very slightly, adapted to the physical environment.

(_b_) =Adaptive relations.=—Organisms depending on other organisms for food or other necessary conditions of life, present many forms of adaptation the better to secure their food and to use it. These adaptations are the consequences and the signs of the assemblage, and are of the greatest service in interpreting the place and significance of the organisms in the assemblage. Teeth usually reveal the food of their possessors, and hence teeth are among the most significant of fossils. Fortunately their functions require them to be hard and durable, and hence well suited to fossilization. The growth of low plants into trees forced a notable series of adaptations in the animals that fed upon them in the matter of height, of reaching members, of climbing, and probably at length of parachuting and flying. In these and similar ways the floras and faunas took on special phases because of the mutual relations of their members.

(_c_) =Competitive relations.=—The assembling of plants and animals, with their prodigious possibilities of multiplication, brought competition, and with it a struggle for food which often became a struggle for existence, and out of this grew innumerable modifications of form and habit. These have become so familiar since the great awakening caused by the doctrines of Darwin and Wallace that they need no elaboration here.

(_d_) =Offensive and defensive relations.=—Within limits, plants are benefited by the feeding of animals and respond by developing seeds and fruits that especially invite such action, their compensation being found in planting and distribution. It is obvious that, on the whole, the continued growth of plants is largely dependent on the renewal of a supply of carbon dioxide through the agency of animals and some plants, bacteria in particular. Otherwise the supply would become so reduced as to greatly limit plant life. It has been estimated[298] that the whole of the present supply of carbon dioxide would be consumed by plants in one hundred years if the consumption continued at the present rate and no carbon dioxide was returned. It is now well known that the so-called decay by which carbon dioxide is freed is due more to microscopic organisms than to inorganic processes. It seems clear, therefore, that the continued activity of plants is largely due to their consumption by animals and other plants. But still, though the larger good of plants is conserved by the predaceous action of animals, and of certain parasitic and saprophytic plants, their individual preservation is often conserved by defensive devices, such as thorns, poisons, bitter compounds, etc. This is notably true in desert regions where the conditions are hard and the total extinction of plants would be threatened if animals were permitted to feed freely upon them. Within the animal world, the preying of one form upon another is the main source of that great struggle for existence which has characterized the whole known history of life, and has been one of the influential factors in shaping the evolution of life and in modifying the special aspects assumed by the floras and faunas of each period.

=Implied forms of life.=—The full meaning of the fossils of any period can only be gathered by duly considering these relationships in their interpretation. The existence of animals implies the existence of plants in supporting abundance, whether the record contains their relics or not; an animal with a protective covering implies an enemy; a tooth of a specific kind implies the appropriate class of food, etc. While inferences of this kind are subject to error, they are at present the only means by which the faunas and floras of most ages can be rounded out into a rational assemblage of organisms, that is, an assemblage that affords the necessary food for its members and an adequate function for the offensive and defensive devices which its members present. Only a small part of the life that lived was fossilized, and only a small part of the fossils actually carried in the strata have been collected, because only a small part of the strata are exposed at the surface. The direct record now accessible is, therefore, very incomplete and hence the need—and in the need the excuse—for adding the forms that are implied by the character of the known fossils.

(2) _Assemblages Influenced by Environment._

It has been noted that some animals depend for existence on other animals; that ultimately all animals depend on plants, and that green plants alone can make food directly from inorganic material. Green plants, therefore, head the train of dependencies, and their relations to the physical conditions that surround them are the primal relations.

=Plant societies.=[299]—The control of physical conditions has been sufficient to develop special associations or societies of plants by fostering those adapted to these conditions and eliminating those that are not. Among these are (1) the hydrophytes (“water plants”), embracing those that grow in water or in very wet situations; (2) xerophytes (“drought plants”), embracing the opposite class, which are adapted to very dry situations; (3) mesophytes, including those suited to conditions lying between these extremes, the great middle class to which the prevailing upland vegetation belongs; and (4) the halophytes (“salt plants”), which are dependent on the presence of certain salts, and embrace such plants as are found on the seacoast, around salt springs, on alkaline flats, etc. The characters which distinguish the xerophytes from the hydrophytes and mesophytes have special geological interest, as they aid in determining the climatic conditions, a feature whose interest increases as the variability of the ancient climates is more fully recognized.

Within these greater groups there are special minor associations determined by soil, temperature, topography, subjacent strata, and by the relations of the plants to one another.[300] These natural groups are valuable indications of the agricultural capabilities of the districts occupied by them. They may be regarded as the outcome of Nature’s experiments in crop-raising, running consecutively through thousands of years. They are natural correlations of compatible members into communities of plants. Some members of the society are obviously dependent on others, as certain forms of undergrowth on the shadowing of the upper growth, as of vines upon supporting-trees, etc. There is probably a more occult relation in some cases, the effects of certain plants on the soil being sometimes advantageous to other plants, and sometimes harmful, as illustrated in the conditions that require a rotation of crops.

The chief point of geologic interest lies in the fact that floras are not mere miscellaneous mixtures of plants that happen to live in a given area at a given period, but are organized communities, in a more or less definite sense. They therefore imply more or less definitely the physical conditions which are congenial to them, and thus furnish the basis for interpreting such conditions in the past, so far as the floras are well preserved. The faunas, especially the land faunas, being primarily dependent on the floras, furnish a basis for interpretations of like import.

B. +The Influence of Geographic Conditions on the Evolution of
Floras and Faunas.+

The geographic features of the earth impose on organisms a complex series of influences which modify the evolution of life and produce faunal and floral variation on a large scale. The larger assemblages of life, which inhabit a continent or dwell in a great sea, are designated faunas and floras, as well as the smaller assemblages just discussed, but obviously in a broader and in a different sense. The disseverance of the land by the sea, or of the sea by the land, isolates the life and forces independent development. The introduction of cold zones, desert tracts, or other potent climatic belts has somewhat the same effect. So, measurably, does the raising of a mountain range or a plateau, or the sinking of critical portions of the sea-bottom.

=The development of provincial and cosmopolitan faunas.=[301]—If a region is isolated from other regions by the cutting off of all ready means of intermigration, as by the formation of an island from what had been a peninsula, or of an inland sea from what had been a bay, the flora and fauna are developed by themselves without much influx of other forms, and hence become local or provincial. This is usually more marked in the case of the fauna than of the flora, because the latter has more ample means of dispersion, on the whole, and so the fauna may for convenience be taken as the type. A good illustration is the native fauna of Australia which was once connected with Asia, but has long been separated from it. Previous to importations by man, this continent had a very peculiar and distinct fauna, descended from its Mesozoic inhabitants. Most of the isolated islands have peculiar faunas, but in many cases they were isolated from the beginning, having been built up by volcanic action from the bottom of the sea, and their faunas are due to the accidents of transportation and to the development of these sporadic forms in isolation.[302]

It is evident that whenever any geographic change introduces a barrier to migration, the faunas of the dissevered portions will, in all probability, develop along different lines, and will diverge into provincial faunas. On the other hand, any geographic change that unites areas and leads to intermigration, tends to a community of fauna or to cosmopolitanism. These tendencies have been markedly felt all through the geologic ages, and constitute one of the most vital features of their history. When continents are connected, their faunas intermingle and the exchange gives rise to common forms. They tend to blend into one great fauna except so far as the local differences develop those minor assemblages previously discussed. When continents are separated, they tend to develop peculiar faunas, as do islands, but on a larger scale. This is very obvious in the case of the land life, but needs more special statement for the oceans.

The oceans constitute a single body of water with ample connections and stirred by a system of constant circulation. Probably this has been true for most of known geologic time. A single cosmopolitan fauna of the largest type might be expected. This is in a measure realized in the pelagic fauna of the open ocean, though this is somewhat modified by the climatic zones. But the marine faunas that are fossilized in the known strata, and have most geologic interest, are, with rare exceptions, not those of the open ocean, but those of the shore zones and of the shallow seas. Now, although these shore belts and shallow seas are broadly connected with the great ocean body, and are usually regarded as a part of it, they are singularly separated from it, or rather they are singularly separated by it, so far as the life dependent on shallow-water conditions is concerned. To this life, the deep sea is a barrier not quite as effective as the land, but still a barrier. The key to this important fact may be found in a consideration of _the vertical distribution of life_.

The great horizon of life is at or near the contact zone of the atmosphere with the hydrosphere and lithosphere. Life declines with increasing altitude, partly because of the lowering temperature, and partly because of the increasing tenuity of the atmosphere. The successive changes of plant and animal life with the ascent of mountains and plateaus is familiar. Life declines in descent into the sea chiefly from lack of light, and secondarily from the lowering of temperature. Light is essential to the formation of chlorophyll and, through it, of all other organic compounds. The chlorophyll-forming plants are, therefore, limited to such depths as are penetrated by the rays necessary for the photosynthesis of organic matter. Vision is cut off within 200 to 300 feet, and most plant growth takes place above that depth. Photographic effects become feeble or inappreciable at 1000 to 1200 feet.[303] The photosynthesis of plants is chiefly aided by the lower and middle part of the spectrum, while the ordinary photographic work is chiefly done by the upper end, so that the photographic limit is below the photosynthetic limit. Microscopic plants are sometimes found lower than these limits, but they may have been carried below their working limits by currents or other incidental agencies. For all general purposes, the limiting depth of living carbon-compounding plants may be set at 100 fathoms, as a generous figure—about the average depth of the border of the continental shelf—while the vast majority flourish only in the upper third of this depth.

Life does not cease here, for the products of this surface-life sink to greater depths and are fed upon by forms of sea animals that have become adapted to the dark and cold abyss of the ocean. Obviously, these deep-sea forms are a very distinct type of life, and constitute a fauna of the most pronounced kind, the abysmal fauna. Another distinct fauna occupies the open-ocean surface, the pelagic fauna. Still a third fauna occupies the shallow-water tract, whose bottom lies within the light zone—_the photobathic zone_—and embraces the animals that are dependent on the plants of this zone, or on its light and warmth, and that are more or less fixed to the bottom or confined to the zone because their food is there.

The physical plane of demarkation between the surface or pelagic fauna and the abysmal fauna is much more distinct and more fundamental than any that is found in ascending above the surface of the sea. The habitat of the shallow-water fauna is limited below by the darkness, limited above by the water-surface, limited at one side by the land, and limited on the other side by the deep sea. It is hemmed in vertically between two planes only a few hundred feet apart. Laterally, it is confined to a narrow belt about the borders of the continents and to the more or less land-girt epicontinental seas. Its vertical limits are fixed, but its lateral extent varies with the relations of the sea to the surface of the continental platforms.

This variation profoundly affects the development of the fauna. When a major deformation of the earth takes place which increases the capacity of the oceanic basins, the water is drawn down into them more fully, and correspondingly retreats from the continental shelf. The shore is thus carried out toward or to the border of the shelf, or even perhaps down to some line on the abysmal slope. In either case, the zone of shallow water suited to the photobathic life is narrowed, and at points it may be practically cut in two. There are, however, shelves and tracts that were below the light zone before, which now are brought within it by the lowering of the sea-level. Into these, as into harbors of refuge, the life migrates so far as it may. But these tracts are less prevalent and continuous than the typical continental shelf, and under the conditions supposed they would be but imperfectly connected with each other by available shallow-water tracts. (The steep shelving shore tracts, although furnishing a shallow-water connection possibly available for some species, would be unsuited to others and, under certain conditions of the sea-currents, would be an effective barrier.) To these limited tracts, therefore, the life of the photobathic type is restricted and measurably isolated, and develops into local and provincial faunas.

After a deforming movement has ceased, the seashore habitually advances, developing a new continental shelf, and in time new epicontinental gulfs and seas. In this it is assisted by the erosion of the continent and the filling of the sea, and probably by the slow settling of the continents. As the sea-shelf broadens, the isolated tracts, the harbors of refuge, become connected, and migration is facilitated. When the connection becomes general and broad, and when epicontinental seas have formed available tracts across the face of the continents, a general commingling of faunas follows, and a cosmopolitan fauna results.

In the same way, but more obviously, when the land is extended and connection between the continents becomes general, there is migration and commingling of the land faunas and floras, and cosmopolitan communities are the result.

It is obvious that the development on the land is the reciprocal of that in the sea. When the seas are extended and their life is tending toward cosmopolitanism, the lands are dissevered, and their life is tending toward provincialism, and _vice versa_. When, however, the land is greatly extended, it is usually accentuated by mountain ranges, and other products of the deformation which extended it, and these form barriers. Desert wastes and other inhospitable tracts, and even glaciation, are liable to develop as secondary consequences, and to interpose barriers, and hence the cosmopolitanism of the land-life is liable to be less complete than that of the sea-life.

=Restrictive and expansional evolution.=—It is obvious from the last discussion that if the picture of the earth’s movement above drawn be true, the areas available for particular classes of life may vary greatly from age to age. At times the shallow-water sea-life may be forced to retreat into a very narrow tract on the border of the land, and into chance expansions here and there. In being crowded into this limited tract, perhaps also less adapted for a habitat on account of the change, the life is subjected to severe competition and to hard conditions, and must experience in an intensified degree the effects of the struggle for existence. Whatever of evolutionary potency there may be in such a struggle under such restrictive conditions should be revealed in the modifications of the fauna that ensued.

On the other hand, when the shallow seas are generally extending themselves upon the land and the land is being base-leveled, and thus adapted to shallow submergence, the shallow-water life enjoys an enlarging realm, and should reveal the effects of evolution under expansional conditions. In affording a comparison between these opposite and alternating phases of restrictional and expansional evolution, geology makes one of its great contributions to the external causes and conditions of organic evolution. These will come under repeated consideration in the historical chapters.

INDEX.

VOLUME I.

Abbot, M. L. (and Humphreys, A. A.), 106, 202

Abrasion,
by ice, 281
by streams, 119
by waves, 342
by wind, 38

Abysmal fauna, 671

Abysmal sea, 326

Accretion hypothesis,
internal temperature on, 564, 567
recombination of material on, 568

Actinolite, 447, 460

Adams, F. D., 474

Adjustment of streams,
structural, 146, 150
topographic, 162, 163, 197

Adobe, 467

Agassiz, 366, 604

Agassiz, L., 321, 322, 323, 366

Agate, 460

Agate structure, 436

Agglomerate, 434, 467

Aggradation,
by ice, 298
by streams, 2, 177
by wind, 25
in sea, 333, 355

Aggrading streams, characteristics, 179, 187

Airy, Sir G., 341

Alabaster, 460

Albite, 400, 460

Alferric rocks, 454

Algæ,
geologic contribution of, 653
influence on precipitation, 225

Alkalicalcic rocks, 458

Alluvial cone, 181–3
growth, 181
levees, 182

Alluvial deposits, 177–96

Alluvial fans, 181–3

Alluvial plains, 181, 184–96
material of, 196
origin of, 184, 185
piedmont, 183
topography of, 196

Alluviation, 181, 196, 467
ill-defined, 183

Alpine glaciers, 251

Alps,
crustal shortening involved in formation of, 549, 576
structure, 504, 507

Amber, 646

Amethyst, 460

Amphibole, 460

Amphiboles, 400

Amygdaloid, 411, 467

Analcite, 460

Analyses,
American river-waters, 107
American spring-waters, 235
rain-waters, 107
river-waters, 106, 107, 108
sea-water, 324
waters of enclosed lakes, 392

Anamorphism, 446

Andalusite, 460

Andes, snow-line in, 246

Andesine, 400, 460

Andesite, 467

Angiosperms, 657

Anhydrite, 460

Animal kingdom,
geologic contribution of, 658–63
synopsis of, 659

Anorthite, 460

Anorthosite, 467

Antarctica, snow-line in, 246

Antecedent streams, 169, 173

Anthracite, 426, 460

Anticlinal valleys, 159

Anticline, 504
plunging, 155, 157, 506

Anticlinoria, 504

Antimony, 460

Apatite, 460

Aphanite, 451, 452, 467

Aplite, 415

Appalachian Riser, 173

Appalachians,
crustal shortening due to folding, 549
extent of piracy in, 169
peculiarities of drainage, 169
rejuvenation of streams in, 165
stream adjustment in, 147

Aqueous rocks, 467

Aragonite, 460

Archean complex, 18

Arch of earth’s crust, strength of, 582

Archeozoic era, 19

Arenaceous rocks, 468

Arid regions, erosion in, 131

Argillite, 448, 468

Arkose, 422, 468, 645

Artesian wells, 242

Arthropoda, geologic contribution of, 662

Asiderites, 5

Asphaltum, 460

Asteroids, 661

Astronomic geology, 1, 2

Atlantic coastal plain, 587

Atmosphere, 5
affected by life, 639, 640
carbonation by, 43
chemical work of, 41–43
evaporation and precipitation, 50
fluctuations in composition, 639–44
geologic activity of, 6, 21–43
mass and extent, 6
mechanical work of, 21–41
oxidation by, 42
thermal effects of, 7

Atmospheric electricity, 43, 52

Atmospheric precipitation, amount of, 51

Augite, 400, 429, 461

Augitite, 468

Autoclastic rock, 444

Australia, fauna of, 668

Babb, C. C., 107

Bad-lands, 93, 130

Badger Mountain, 231

Bain, H. F., 67, 474

Barbadoes earth, 661

Barite, 461

Barrier, the, 356

Bars, 181, 357

Barus, Carl, 562, 563

Basalt, 417, 452, 468

Basaltic columns, 417

Base-level, 60, 62, 82, 168
Cretaceous, 169
Kiltatinny, 168
temporary, 84

Basement complex, 18

Batholiths, 500, 592

Bayou, 192

Bayou lakes, 193

Bays, origin of, 331, 332

Beach, the, 355

Beauxite, 461

Beck, R., 474

Becker, G. F., 474

Bergschrund, 258

Bertin, 323

Beryl, 461

Bighorn Mountains, lateral moraines in, 302

Biotite, 400, 461

Bischoff, Gustav, 108

Bismuth, 461

“Bittern,” 377

Bitumen, 461

Bituminous coal, 426, 468

Blake, W. P., 474

Blanford, W. T., 28, 203

Blood rain, 25

Blue mud, 380

Bone beds, 663

Bonneville lake, 360

Bonneville shore, 352

Bottom-set beds, 202

Bowlders, 468

Brachiopods, geologic contributions of, 662

Brahmaputra delta, 203

Branner, J. C., 489

Breakers, 341
force of, 344

Breccia, 423, 434, 468

Britannare, 459

Bronzite, 461

Bryozoans, geologic contributions of, 662

Buckley, E. R., 48, 50, 221

Buhrstone, 468

Burton (and Milne, J.), 636

Buttes, 142

Bysmaliths, 500, 592

Calcareous springs, 235

Calcareous tufa, 390

Calcimiric rocks, 458

Calcite, 461

Calc-sinter, 468

Calumet and Hecla mine, temperature in, 569

Calvin, S., 88, 204, 373, 389

Campbell, M. R., 167, 171, 173

Camphene, 646

Cannel coal, 468

Canoe-shaped valleys, 155

Canyons, 94–100
Colorado, 98, 233
Niagara, 99
Yellowstone, 100

Carbonation, 43, 429

Carbon dioxide,
amount in air, 5, 640
and plant-life, 665
climatic effects of, 643
loss of, 640
supply of, 618, 640

Cascade, 264

Cassiterite, 461

Catlinite, 461

Causes of crustal movement, 551–557

Caverns (see Caves)

Caves, 143, 227–231
deposits in, 228
Mammoth, 227
sea, 350
Wyandotte, 227

Cazin, F. M. F., 474

Cementation,
effected through chemical precipitation, 222, 225, 226
effected through evaporation, 42

Cephalopods, geologic contributions of, 662

Chalcedony, 461

Chalk, 468, 660

Challenger deep, 587, 588

Chalybeate springs, 235

Chamberlin, T. C., 23, 242, 256, 322, 477, 565, 668

Changes of level, 537–551
caused by earthquakes, 536
causes of, 551–557
effect on drainage, 161
sea _versus_ land, 538

Changes of temperature,
conditions affecting, 45
effect on rocks, 44, 49
internal (see Internal temperatures)

Charleston earthquake, 530

Chatter marks, 284

Chemical combination, cause of crustal movement, 556

Chemical deposits, 222–26
in deep sea, 383
in lakes, 391
in shallow sea, 374–378

Chemical work of atmosphere, 41–43

Chemical work of life, 638–46

Chert, 426, 468

Chiastolite, 461

Chimney rocks, 350

Chlorite, 461

Chlorite schist, 468

Chloritic rock, 431

Chromite, 461

Chrysolite, 462

Chrysotile, 462

Cinder-cones, 608

Cinders, 405

Cirques, 286

Clarke, F. W., 396, 573

Classification of rocks, 449
new system of, 451

Clastic rock, 468

Clay, 468

Clay ironstone, 468

Claypole, E. W., 549

Cleavage planes and erosion, 125
development of (see Slate and Schist)

Cliff glacier, 256

Climate, influence on erosion, 127–132

Climatic effects of carbon dioxide, 643

Climatic effects of life, 643

Climatic effects of water vapor, 643

Clinkstone, 468

Clinometer, 501

Coal, 468

Coast-lines 353, 363–6
effect of gradation on, 333, 363
effect of subsidence on, 329, 332
effect of vulcanism on, 332–33
forms of, 329, 333, 363, 364

Coast ranges, crustal, shortening due to folding of, 549

Coasts, natural bridges on, 351

Cobb, C., 36

Cœlenterata, geologic contribution of, 661

Collins, A. L., 474

Colorado, Canyon of, 98, 233

Columbia River, 171

Columnar structure, 498–500
effect on weathering, 153, 154

Common springs, 235

Compression joints, 514

Concave tracts of crust, 585, 586

Concretions, 438, 468, 490

Cones,
cinder, 608
composite, 610
formation of, 608
geyser, 237
lava, 608
spatter, 610
tufa, 611

Configuration of coasts, 329, 330, 331, 332, 333, 353, 363–6

Conformability, 15

Conglomerate, 423, 434, 468, 487

Continental glaziers, 251

Continental platforms, 11
relief of, 11

Continental segments, size of, 547

Continental shelf, 11

Continent-forming movements, 544

Contour interval, 31

Contour lines, 31

Convection hypothesis,
internal heat on, 559
thermal distribution on, 559

Cooley, E. G., 195

Coon Butte, 596

Copalite, 646

Coprolites, 646

Coquina, 469

Coral mud, 380

Cornish, V., 26, 28, 29

Corrasion, 110, 113
by glaciers, 281–86
by streams, 119
by waves, 342–49
by wind, 38
effect of sediment on, 120

Corthell, E. L., 202

Cosmopolitan faunas, 668

Coulter, J. M., 667

Coves, 143

Cowles, H. C., 35, 667

Credner, H., 35, 538

Creep, 231

Cretaceous base-level, 169

Crevasses, 264

Crinoids, 661

Croll, James, 322, 323, 339

Crosby, W. O., 513

Cross-bedding, 373, 487

Cross-currents, in streams, 117

Cross, Whitman, 412, 451, 535, 573

Croton River, material in solution in, 108

Crustal movements, 526–589
causes of, 551–57
differential extent of, 548
due to chemical changes, 556
due to cohesion and crystallization, 554
due to diffusion, 555
earthquake, 527–33
minute and rapid, 526
periodicity of, 517, 539
resistance to, 557
slow and massive, 537–59

Crustal shortening, 548–51

Crust of earth, 13
depth of, 14
varieties of rock in, 14

Crystalline rocks, types of, 16

Crystallites, 407

Crystallization of lava, 401–2
stages of, 403

Crystals, enlargement of, 435

Cut-and-fill, 190, 193

Cut-off, 191

Cycle of erosion,
its stages, 80
definition of, 82
recognition of, 164

Cystoids, 661

Dacite, 469

Dale, T. N., 505

Daly, R. A., 631

Dana, J. D., 203, 340, 349, 511, 543, 604, 636

Daniell, A., 572, 573

Danube River,
delta of, 202
material in solution in, 108
sediment carried by, 107

Darton, N. H., 41, 50, 53, 94, 135, 154, 494, 570

Darwin, C., 604, 636, 665

Darwin, G. H., 534, 561, 576, 579, 583, 604

Daubree, G. A., 626

Davis, B. M., 225

Davis, W. M., 83, 159, 164, 170, 188, 202, 204 210 349,
and Shaler, N. S., 256

Davis, C. A., 655

Davison, C., 527, 538, 561

DeBeaumont, Eli, 323

Decarbonation, 429, 430

DeCharpentier, J., 321, 322, 323

Deeley, R. M., 322

Deep-sea deposits, 368, 378–86
chemical, 383–86
extra-terrestrial, 381
inorganic, 380
manganiferous, 384
organic, 382

Deep-sea fauna, 670

Deposition,
by glaciers, 298–305
by streams, 177–204
by shore currents, 355
by undertow, 355
by waves, 355–63
by wind, 25–37

Deformation of earth’s crust, 526–89
causes of, 551–57, 574–89
relation to distribution of volcanoes, 601, 604, 627, 629

Deformation of ice, 312

Degradation, 2
by water, 58–177
rate of, 105

De Launay, L. C., 474

Delesse, A., 221, 341

Delessite, 462

Dells of the Wisconsin, 152

Delta lakes, 204

Deltas, 181, 198–204
bottom set beds, 202
development, 199
fore-set beds, 202
fossil, 203
in tidal seas, 202
of the Ganges and Brahmaputra, 202
of the Hoang-Ho, 202, 203
of the Mackenzie, 202
of the Mississippi, 197, 202
of the Nile, 202
of the Po, 202
of the Rhone, 203
of the Yukon, 202
rate of growth, 202
shape, 201
structure, 198, 199
top-set beds, 202

Densities within the earth, on Laplace’s law, 564

Denudation and volcanic action, 627

Deoxidation, 427

Deposition of mineral matter from solution, 50, 225, 428
at surface, 50, 224
by ground-water, 224, 428
in lakes, 387
in sea, 375, 383

Deposition of sediment, 66
by rivers, 177–204
by wind, 25–38
in ocean, 355–63, 368–86

Deposition of drift, at edge of glaciers, 299
at end glaciers 299
beneath ice, 298

Deposits,
deep-sea, 368, 378–86
hot springs, 237, 241
lacustrine, 387
littoral, 369
made by animals, 658–63
made by Arthropoda, 662
made by Bryophytes, 656
made by Echinodermata, 661
made by ice, 298–305
made by Mollusca, 662
made by Molluscoidea, 662
made by Protozoa, 660
made by Pteridophytes, 657
made by plant kingdom, 652–58
made by rivers, 177–204
made by Spermatophytes, 657
made by Thallophytes, 653
made by Vermes, 662
made by Vertebrata, 663
made by wind, 25–38
shallow-water, 369–78
silicious, 237, 241, 425
tufa, 237, 241, 473, 611, 653

Depression and volcanic action, 629

Depth of the ocean, 7
greatest, 8, 548

Diabases, 418, 431, 469

Diallage, 400, 462

Diastrophism, 2, 329, 526
effect on coast lines, 329

Diatom ooze, 380, 382, 425, 469

Diffusion,
in earth’s interior, 555
cause of crustal movement, 555

Dikes, 591
effect on topography, 143
sandstone, 514

Diller, J. S., 29, 514

Diorites, 416, 452, 469

Dip, 501
quaquaversal, 504

Dip-fault, 522

DiRossi, M. S., 537

Displacement of fault, 514

Disruption of rock, due to changes of temperature, 44, 49
by carbonation, 43
by hydration, 111

Distributive fault, 519

Divides, permanence of, 69

Docalcic rocks, 458

Dodge, R. E., 204

Dofemane, 455

Dofemic rocks, 454

Doferrous rocks, 459

Dohemic rocks, 457

Dolenic rocks, 456

Dolerites, 417, 452, 469

Dolomites, 424, 469

Domagnesic rocks, 459

Domalkalic rocks, 458

Domes of crust, strength of, 581, 582

Domilic rocks, 582

Domiric rocks, 458

Domirlic rocks, 458

Domitic rocks, 457

Dopolic rocks, 456

Dopotassic rocks, 458

Dopyric rocks, 457

Doquaric rocks, 456

Dosalic rocks, 454

Dosodic rocks, 458

Dotilic rocks, 457

Drainage,
effect of change of level on, 161
mature, 86
of glaciers, 273
old age, 89
youthful, 86

Dreikanter, 40

Drift, 287, 469
composition of, 304
deposition of, 298–305
wear of, in transit, 298

Drygalski, E. von, 322

Dump moraine, 301

Dune areas, topography of, 32

Dunes, 24–37
distribution of, 35
effect of vegetation on, 29
formation of, 26
migration of, 33
shapes of, 26
slopes of, 29

Dust,
volcanic, 22, 23
wind-blown, 22

Dust-wells, 269, 280

Dutton, C. E., 132, 534, 574, 636

Dynamic geology, 1

Earth, the,
as a planet, 2
constitution, 5
crust, 13
deformation of, 526
dependence on sun, 4
distance from sun, 3
inclination of axis, 3
interior of, 14, 559
internal heat, 559–74
motions, 3
orbit, 3
tremors of surface, 526
warpings of crust, 526–89

Earthquakes, 527–537
causes of, 527
destruction of life by, 536
distribution of, 533
destructive effects of, 530
epicentra of, 531
foci of, 527
gaseous emanations during, 533
geologic effects of, 534–537

Earthquake vibrations, 526
amplitude of, 529
Charleston, 534
Lisbon, 535
sequences of, 533

Earth’s crust,
composition of, 14, 396
warpings of, 538–551

Eastman, C. R., 658

Echinodermata, geologic contributions of, 661

Echinoids, geologic contributions of, 661

Economic geology, 1

Efflorescence, 42

Elæolite, 462

Electricity,
atmospheric, 43
chemical effects of, 43
geological effects of, 43, 52

Ells, R., 443

Emmons, S. F., 474

Emmons, W. H., 474, 573, 585

Englacial drift, 282

Enlargement of crystals, by secondary growth, 435

Enstatite, 400, 462

Eolian rocks, 469

Epeirogenic movements, 537

Epicontinental seas, 11, 326

Epidote, 431, 462

Equisetæ, geologic contribution of, 657

Eras, 17–19

Erosion,
affected by rotation, 194
analysis of, 110
base-level of, 60
by glaciers, 281–286
by rain, 57
by rivers, 56–177
by undertow, 342, 346
by waves, 342–349
by wind, 38
conditions affecting rate of, by glaciers, 283
conditions affecting rate of, by running water, 123
cycle of, 80, 82, 164
in arid regions, 131
influenced by climate, 127, 128, 129
influenced by composition of rock, 124
influenced by declivity, 123
influenced by structure, 124, 126
influenced by vegetation, 129, 644
sheet, 59
subaërial, 58

Erosion and cleavage planes, 125

Erosion and joints, 125

Erosion by streams (see Erosion by running water)

Eruptions, 591
fissure, 593
volcanic, 594

Eskers, 306

Etna, 605, 610
discharge of stream from, 636

Evaporation, 50

Everett, 578

Evolution restrictive and expansional, 672

Exfoliation, 44

Expansional evolution, 672

Expansion and contraction,
due to temperature, 44
due to wetting and drying, 52

Extinct lakes, 388

Extrusive processes, 590–637

Falb, R., 537

False bedding, 487

Faulting and vulcanism, 627

Faults,
conditions of, 521
dip, 522
displacement, 514
distributive, 519
effect on outcrops, 522
hade, 514
heave of, 514
normal, 517
oblique, 525
relation to folds, 515
reversed, 517, 521
stratigraphic throw, 518
significance of, 521
strike, 522
thrust, 517, 518

Fault scarp, 514

Faunas,
abysmal, 670
Australian, 668
cosmopolitan, 668
deep-sea, 670
pelagic, 670
photobathic, 670

Faunas and floras,
basis of, 663
effect of geographic conditions on evolution of, 668

Feldspar, 462

Feldspar-leucophyres, 453

Feldspar-melaphyres, 453

Feldspathic minerals, 400

Feldspathoids, 400

Felsites, 452, 469

Fenneman, N. M., 339

Ferguson, A. M., 203

Ferns, geologic contribution of, 657

Fiords, 290

Fisher, O., 561, 565, 574, 581

Fissure eruptions, 593

Fletcher, G. (and Deeley, R. M.), 322

Flints, 426, 469

Floods, 109
of the Mississippi, 188

Flood-plain meanders, 190
Flood-plains, 184–98
development of, 165
materials of, 196
Mississippi, 194
relation to terraces, 205
topography, 196

Floras and faunas,
basis of, 663
effect of geographic conditions on, 668

Flowering plants, geologic contributions of, 657

Flowing wells, 234, 242

Flow structure of lavas, 410

Fluorite, 462

Fluvio-glacial work, 305–7

Folded ranges, distribution of, 543

Folding and vulcanism, 628

Folds,
anticlinal, 504, 505
effect on valleys, 154
isoclinal, 504
synclinal, 504

Folds and faults, 515

Foliation of ice, 272

Foliation of rocks, 443

Foraminifera, geologic contribution of, 660

Forbes, J. D., 256, 322

Forel, F. A., 323, 386

Fore-set beds, 202

Formation, 487

Forster, W. G., 536

“Fossil” deltas, 203

Fossils, 16, 646
a means of correlation, 647

Fossils and stratigraphy, 647

Fouqué, F., 635, 636

Fracture, zone of, 219

Frank, A. B., 642

Freestone, 469

French Broad River, the, 168

Fulgurites, 52, 469

Fungi, geologic contribution of, 653

Gabbroids, 453

Gabbros, 416, 452, 469

Galenite, 441

Ganges River, delta of, 203

Gangue, 469

Gannister, 469

Garnet, 462

Garnetite, 469

Gaseous emanations,
during earthquakes, 533
from volcanoes, 617

Gases in volcanic rocks, 619

Gases, volcanic, 617–623
amount of, 620
kinds of, 618, 619
proportions of, 620, 622
sources of, 621

Gastropods, geologic contributions of, 662

Geantcline, 505

Geest, 469

Geikie, A., 203, 224, 344, 534–536, 636

Geodes, 436, 497

Geognosy, 1, 5, 393–485

Geologic effects of earthquakes, 534

Geologic functions of life, 638

Geologic processes, man’s influence on, 649

Geologic time divisions, 19

Geology,
astronomic, 1, 2
atmospheric, 2
cosmic, 1
dominant processes of, 2
dynamic, 1
economic, 1
geotectonic, 1, 486
glacial, 2
historical, 1
mining, 1
paleontologic, 1
philosophic, 1
physiographic, 1
scope of, 1
structural, 1, 486
subdivisions of, 1

George, R. D., 545

Geosyncline, 505

Geotectonic geology, 1, 486–525

Gerber, E., 195

Gerland, 538

Geschiebe wall, 300

Geyserite, 463, 469

Geysers, 236
deposits of, 237
of Yellowstone Park, 239
period of eruption, 240
positions of, 241

Gilbert, G. K., 11, 110, 140, 194, 198, 203, 339, 355, 388, 489, 596

Glacial débris,
how carried, 290
nature of, 286
shifting position in transit, 292, 293, 294, 296, 297

Glacial deposits, nature of, 304

Glacial erosion,
conditions influencing, 283
topographic effects of, 287

Glacial motion, 313–321
auxiliary elements of, 317
fundamental element of, 313

Glacial plucking, 282

Glaciated rock surfaces, 304

Glacier ice,
beginning of movement, 248
definition of, 250
granular texture of, 247
shearing of, 317

Glacier movement, 259, 313–323
at low temperature, 279
effect of water on, 318
rates, 260, 261
views of, 321

Glaciers,
alpine, 254
cliff, 256
compared with rivers, 262
conditions influencing movement, 261
constitution, 308
continental, 251
crevasses, 264
deformation, 312
drainage of, 273, 280
foliation, 247, 272
evaporation, 279
general phenomena, 256
getting load, 282
growth of, 308
growth of granules, 310, 311
high-latitude, 254
limits of, 258
motion in terminal part, 316
movements of, 259, 279, 313–323
piedmont, 254
polar, 254
rate of movement of, 260, 261
reconstructed, 256
stratification of, 247
structure of, 308
surface features of, 266
temperature of, 273–279
thickening of layers at end, 297
topography of, 266
types of, 251
upturning of ice at ends and edges, 296, 297, 298
valley, 254
waste of, 273
work of, 244, 281

Glacio-fluvial work, 305–308

Glass, volcanic, 451

Glassy rocks, 406

Glauconite, 384, 386, 463

Globigerina ooze, 380, 382, 660

Globulites, 407, 469

Gneiss, 415, 446, 448, 469

Gooch, F. A. (and Whitfield, J. E.), 236

Gorge, 100

Grad, Ch., 322

Gradation, 2
by running water, 56–212
effect on coast-lines, 334
in ocean, 334

Grade, 61

Graded plain, 82, 169

Graded valley, 83

Granitell, 470

Granites, 413, 452, 469

Granitite, 470

Granitoids, 420, 453

Granulite, 470

Graphite, 426, 463

Gravitational energy, 552

Gravitational force, 552, 553

Gravity,
a cause of crustal movements, 552
effect on erosion, 113

Gray, T. (and Milne, J.), 578

Greenland,
glaciers of, 246
snow-fields of, 245
snow-line in, 246

Green mud, 380

Greensand, 470

Greensand marl, 386

Greenstone, 419, 470

Greisen, 415, 470

Greywacke, 470

Ground ice, 119

Ground moraine, 301

Ground-water, 213–243
affects internal heat, 570
amount of, 221
descent of, 213
fate of, 221
lower limit of, 216
movement of, 220
results of, 226
solution by, 222, 223
work of, 222

Ground-water and vulcanism, 635

Ground-water level, 71, 215

Ground-water surface, 71, 215

Guano, 646

Gulf stream, 366

Gullies, growth of, 63

Gymnosperms, geologic contributions of, 657

Gypsum, deposition of, 376, 377

Hade of faults, 514

Hall, Jas., 511

Halleflinta, 470

Halophytes, geologic contributions of, 667

Hanging valley, 164, 290

Haüynite, 463

Hayes, W., 173

Hayes, W. (and Campbell, M. R.), 171

Head erosion, 64

Heat, by compression of ice, 311
causes crustal movement, 557
causes of, in ice, 278, 279
distribution of, within earth, 559
distribution, original, 559
internal, of earth, 559–570
metamorphism by, 446, 448
original distribution of, 559

Heave of faults, 514

Heilprin, A., 636

Heim, A., 256, 322, 549, 576

Hematite, 425, 447, 463

High-latitude glaciers, 254

Himalayas, snow-line in, 246

Historical geology, 1

Hoang-Ho delta, 202, 203

Hog-backs, 142

Holden, E. S., 538

Holmes, W. H., 99

Holocrystalline rock, 412

Holosiderites, 5

Hook (along shore), 363

Hopkins, W., 322

Horizontal configuration of coasts, due to deposition, 363, 364
due to wave erosion, 353

Hornblende, 400, 463

Hornblende-granite, 415

Hornblendite, 417, 452, 470

Hornstone, 470

Horsetails (see Equisetæ)

Hoskins, L. M., 219, 552, 581

Hot springs, deposits of, 225

Howell, Capt., 171

Hudson River, material in solution in, 108

Hugi, F. J., 321

Hull, E., 636

Humphreys, A. A. (and Abbot, M. L.), 106, 202

Huxley, T. H., 322

Hyalite, 463

Hydration, 43, 222
disruption of rock by, 111

Hydrophytes, geologic contributions of, 667

Hydrosphere, the, 7 (see also Ground-water and Ocean)
geologic activity of, 8
horizons of activity, 9

Hypersthene, 400, 463

Hypogene rocks, 470

Ice, glacial (see Glaciers)
ground, 119
of lakes, 389
of rivers, 118

Icebergs, 307

Ice-caps, 249, 250

Ice crystals, arrangement in glacier ice, 311

Ice-fall, 264

Iceland spar, 463

Iddings, J. P., 412, 451, 573, 614, 636

Igneous rocks, 16
composition of, 395
leading minerals of, 399
origin of, 393
relations to stratified rocks, 16
structural features of, 498

Ilmenite, 463

Incrustation, 223

Infusorial earth, 470

Inorganic deposits, in deep sea, 380

Interior of earth, 14 (see Vulcanism)
densities, based on Laplace’s law, 564
heat of, 562, 564
pressures, 564

Intermittent springs, 235

Internal heat (see Internal temperature)

Internal temperature, 562
affected by ground-water, 570
at centre of earth, 571
on accretion hypothesis, 564, 567
on convection hypothesis, 559
on Laplacian hypothesis, 559

Intrusions, 591

Iron-ore beds, origin, 425

Iron oxide, 400

Iron pyrites, 463

Ironstone, 425, 470

Irruptions, 591

Isoclinal folds, 504

Isoseismals, 532

Itacolumite, 470

Italy, lateral moraines in, 303

Jasper, 470

Jefferson, M. W., 193

Johnson, S. W., 109, 190, 665

Johnston-Lavis, H. J., 636

Joints, 510
causes of, 511, 531
compression, 514
effect on valleys, 150

Joints, tension, 514

Joints and erosion, 125

Judd, J. W., 636

Kaaterskill Creek, piracy of, 105

Kames, 307
serpentine, 306

Kansas, volcanic dust in, 23

Kanawha River, 168

Kaolin, 463

Katamorphism, 446

Keith, A., 442, 444

Kelvin, Lord, 560, 583

Keratophyre, 470

Kersantite, 470

Keyes, C. R., 474

Kidd, D. A., 313

Kilauea, 605

King, C., 560

King, F. H., 220

Kittatinny base-level, 168

Kotö, Dr., 534

Krakatoa, 22, 610, 611, 618

Kümmel, H. B., 203

Labradorite, 400, 429, 464

Laccolith, 500, 592

Lacustrine deposits, 388

Lake ice, 389

Lake Pepin, 179

Lakes, 386–392
bayou, 192, 193
changes taking place in, 387
delta, 204
deposits in, 387
extinct, 388
formed by rivers, 191, 192, 198
ice of, 389
ox-bow, 192, 198

Landslide, 231
topography of, 230

Landslip mountain, 230

Lane, A. C., 557, 636

Lapilli, 470
in sea, 381, 405

Laplace, Marquis de, 564

Laramide range, crustal shortening due to folding, 549

Lateral moraines, 266, 302
in Bighorn Mountains, 303
in Italy, 303
in Uinta Mountains, 303
in Wasatch Mountains, 303

Lateral pressure, metamorphism by, 448

Laterite, 470

Lava cones, 608

Lavas, 612–616
and ground-water, 616
consanguinity and succession of, 614
crystallization of, 402, 403
depth of source of, 616
modes of reaching surface, 631
origin of, 623–631
rhyolitic (flow) structure of, 410
solidification of, 393
temperatures of, 615, 626

Lavas and underground water, 627

LeConte, J., 474, 549

Lendofelic, 456

Lenfelic, 456

Lepidolite, 464

Leucite, 464

Leucophyre, 412, 453

Levees, breaking of, 188
miniature, 182
natural, 188
on alluvial cones, 182

Level of no stress, 561

Life, 638–672
atmospheric effects of, 638–644
chemical work of, 638–646
climatic effects of, 643
effect on rock decomposition, 130, 644
geologic effects of, 639
inorganic rocks due to, 646
influenced by environment, 666
man’s influence on, 650
protection against erosion, 130, 644

Life and carbon dioxide, 640, 642, 643

Lightning, effects of, 52

Lignite, 426, 470

Limburgite, 470

Lime carbonate, deposition of, 375, 376

Limonite, 425

Limestone, 378, 424, 434
origin of, 378, 654, 655
stratification of, 487

Limestone-forming animals, 660–662
plants, 654, 655

Limestone sinks, 227, 231

Lindgren, W., 474

Liparase, 459

Liparite, 470

Lisbon earthquake, 535

Lithosphere, 9–19
crust of, 13
irregularities of, 10
relief of, 11
size and shape of, 9
surface mantle of, 12

Littoral currents, 342

Littoral deposits, 368, 369, 379

Littoral zone, 369

Liverworts, geologic contribution of, 656

Livingstone, D., 49

Load (of streams), 177–179

Loess, 23, 470

Lodge moraine, 301

Loop (along shore), 357, 363

Lunar craters, 598

Lunn, A. C., 552, 565, 566, 567, 572

Lycopods, geologic work of, 657

Lydekker, R. (and Nicholson, A.), 658

Lyell, Sir Charles, 649

Mackenzie River, delta, 202

Magma, nature of, 401

Magnesite, 464

Magnesium salts in sea, 377

Magnetic nodules in sea, 381

Magnetite, 464

Malay peninsula, tin ores of, 478

Malaspina glacier, 254

Mallet, R., 322, 537, 538, 628, 636

Mammoth Cave, 227

Mammoth hot springs, 654

Manganiferous deposits, 384

Mantle rock, 12, 422

Marble, 447, 471

Marcasite, 464

Marine deposits, 355–363, 370–386
chemical, 367, 375, 383
deep-sea, 368, 378–386
extra-terrestrial, 381
littoral, 368, 369
mechanical, 369, 380
organic, 375
shallow-water, 369–378
table of, 380

Marine life, distribution of, 328

Marl, 471 (see also Greensand marl and Shell marl)
formed by plants, 655
green-sand (see Greensand marl)

Martinique, 605

Martite, 464

Mason, W. P., 107

Mass action, 478, 484, 554

Mature drainage, 86

Mature streams, characteristics of, 86

Mauna Loa, 605, 606, 624