Archibald Geikie.

Geology online

. (page 31 of 31)
Online LibraryArchibald GeikieGeology → online text (page 31 of 31)
Font size
QR-code for this ebook


neolithic period.

The stone articles of human workmanship found in neolithic
deposits consist of polished celts and other weapons, hammers,
knives, and many other implements of domestic use. Knives,
needles, pins, and other objects were made out of bone or horn.
There is evidence also that the arts of spinning, weaving, and
pottery-making were not unknown. The discovery of several
kinds of grain shows that the neolithic folk were also farmers.
Vast numbers of these various relics have been found at the pile-
dwellings of Switzerland and other countries. For purposes of
security these people were in the habit of constructing their
wooden dwellings in lakes on foundations of beams, wattled-
work, stones, and earth. Sometimes these erections were apt
to be destroyed by fire, as well as to decay by age. And their
places were taken by new constructions of a similar kind built
on their site. Hence, as generation after generation lived there,
all kinds of articles dropped into the lakes were covered up in
the silt that slowly gathered on the bottom. And now, when
the lakes are drained, or when their level is lowered by pro-
longed drought, these accumulated droppings are laid open for
the researches of antiquaries and geologists. Many important
relics of neolithic man have likewise been obtained from the
floors of caverns and rock-shelters places that from their con-
venience would continue to be used as in palaeolithic time. In-
teresting evidence, also, of the successive stages of civilisation
reached by early man in Europe, is supplied by the older Danish
peat-bogs, in the lower parts of which remains of the Scotch fir
(Pinus sylvestris), a tree that had become extinct in that country
before the historic period, are associated with neolithic imple-
ments. In a higher layer of the peat, trunks of common oak are
found, together with bronze implements, while in the uppermost
portion, the beech-tree and iron weapons take their place.

Between the neolithic and the present period no line can be
drawn. They shade insensibly into each other, and the ma-
terials which reveal the history of their geographical and climatal
vicissitudes, their changes of fauna and flora, and their human
migrations and development, form a common ground for the
labours of the archaeologist, the historian, and the geologist.

During the Kecent period the same agencies have been and



380 GEOLOGY

are at work as those which have been in progress during the
vast succession of previous periods. In the foregoing pages we
have followed in brief outline each of these great periods, and
after this survey we are led back again to the world of to-day
with which the first chapters of this book began. In this circle
of observation no trace can anywhere be detected of a break in
the continuity of the evolution through which our globe has
passed. Everywhere in the rocks beneath our feet, as on the
surface of the earth, we see proofs of the operations of the same
laws and the working of the same processes.

Such, however, have been the disturbances of the terrestrial
crust that, although undoubtedly there has been no general
interruption of the Geological Eecord, local interruptions have
almost everywhere taken place. The sea-floor of one period has
been raised into the dry land of another, and again, the dry-
land, with its chronicles of river and lake, has been submerged
beneath the se^. Each hill and ridge thus comes to possess its
own special history, which it will readily reveal if questioned
in the right way.

We are surrounded with monuments of the geological past.
But these monuments are being slowly destroyed by the very
same processes to which they owed their origin. Air, rain,
frost, springs, rivers, glaciers, waves, and all the other con-
nected agents of demolition, are ceaselessly at work wherever
land rises above the sea. It is in the course of this demolition
that the characteristic features of the scenery of the land are
carved out. The higher and harder parts are left as mountains
and hills, the softer parts are hollowed out into valleys, and the
materials worn away from them are strewn over plains. And
as it is now, so doubtless has it been through the long ages of
geological history. Decay and renovation in never-ending cycles
have followed each other since the beginning of time.

But amid these cycles there has been a marvellous upward
progress of organic being. It is undoubtedly the greatest tri-
umph of geological science to have demonstrated that the present
plants and animals of the globe were not the first inhabitants
of the earth, but that they have appeared only as the de-
scendants of a vast ancestr} 7 ", as the latest comers in a majestic
procession which has been marching through an unknown series
of ages. At the head of this procession we ourselves stand^



POST-TERTIARY PERIODS 381

heirs of all the progress of the past and moving forward into the
future wherein progress towards something higher and nobler
must still be for us, as it has been for all creation, the guid-
ing law.

THE END.



INDEX.



Accumulations formed by the sea,

77

Adelsberg caverns, 55
Age of reptiles, the Jurassic, 316
Albian stage of the Jurassic period,

334

Alluvium, how formed, 35
Aluminium, 125
Ammonites in the triassic period,

305

in the Jurassic period, 313
Amphibians of the carboniferous

period, 284, 286
Amphibolites, 176
Anchor-ice, 63
Anhydrite, 141
Animals as causes of change on

earth's surface, 18
durable parts of, 223
geological records made by,

83-95
deposits formed by remains of,

87

remains in sedimentary depos-
its, 91

of the tertiary periods, 339
Annelids in cambrian period, 253
Apatile, 141
Aragonite, 140
Archaean rocks, 242
Archaeopteryx, 318, 319
Atlantosaurus, 318
Atmosphere, influence of on

changes of earth's surface,

10-23

Augite, 138
Avalanches, 64
Axmouth landslip, 52

Bajocian stage of Jurassic period,

321
Bathonian stage of the Jurassic

period, 321
Barytes, 141
Barium, 127
Basalt-rocks, 171
Birds first appear in the Jurassic

period, 318, 319
in the cretaceous period, 332
of the eocene period, 342



383



Blow-holes, 73

Bosses, in eruptive rocks, 209

Bone-beds, 167

Boulders transported by ice, 63

Brachiopods of the devonian pe-
riod, 274
in the carboniferous period,

290

of the permian period, 298
of the Silurian period, 265

Breccia, 155

Brick-earth, 20

Brontosaurus, 318

Cainozoic rocks. See Tertiary

Periods.

Calcareous springs, 57
Calcite, 139
Calcium, 125, 127
Calcareous tufa, 59
Gale-sinter, 59
Cambrian period, 246-257
Carbon, 122
Carbonates, 139
Carboniferous period, 277-294
Caverns formed by springs, 55
Cenomian stage of the Jurassic

period, 334
Cephalopods in cambrian period,

256
in the carboniferous period,

291
characteristic of the triassic

period, 305

in the cretaceous period, 329
in the cretaceous period, 330
Chalk, 164

Chalybeate springs, 61
Chemical action of running water,

25-27

Chemical action of springs, 54
Chlorides, 142
Chloride-schist, 176
Chlorine, 124
Chlorite, 138
Concretions, 143
Chronology, geographic shown by

fossils, 228
Clay, 158



384



INDEX



Clay-slate, 175

Cleavage of rocks, 201

Cliff-debris, 154

Climatic changes shown by fossils,

227

Coal, 165

Coal seams as indicative of sub-
sidence, 279, 280
Coal, how formed, 280
Concretions, 186
Concretionary rocks, 147
Conglomerate, 156
Conifers in the permian period,

298

Consolidation of sedimentary de-
posits, 193
Continents formed in tertiary

periods, 339

Coral-reefs, how formed, 89-90
Coral-rock, 164

Corals of Silurian period, 261
of the devonian period, 273
of the devonian period, 275
in the carboniferous period,

287

in the j"^assic period, 311
Corralian stage of the Jurassic

period, 322

Cretaceous period, 324-337
Crinoids or sea-lilies, 253
of silurian period, 261
in the carboniferous period,

288

in the triassic, 305
in the Jurassic period, 311
Crustaceans of the devonian period,

272
in the carboniferous period,

289

in the Jurassic period, 314
Crystal forms, 129-131
Crystalline, 148
Cteosaurus, 317
Curvature of strata, 198
Cuttle fish in the Jurassic period,

313

Cycads in the permian period, 298
in the Jurassic period, 310
age of, 304

Danian stage of the Jurassic period,

336

Dead Sea, 50
Dendrites, 135
Deposition by running water, 35-

43

Deposition by springs, 56
Devonian period, 268-276
Diabase, 173
Diatoms, 86
Dinosaurs first appear in the trias-

sio period, 307
in the Jurassic period, 317



Diorite, 173

Dip of strata, 195

Dislocation of strata, 203

Dolomite, 140, 161

Dust, changes wrought by, 20

Earth, hot interior of, 7

interior, condition of, 97
crust, structure of, 179-234

Earthquakes, 114-118

Earthworms, effect of on soil, 18

Echinodermata, in Cambrian pe-
riod, 253
of silurian period, 262

Elements and minerals, 119

Erosion, 30-35

Erosion, geological effect of, G8

Erosive power of running water, 25

Erratic boulders, 66

Eruptive rocks, 148

Eruptive rocks, 167-180

Eruptive rocks, 208

Eocene period of the tertiary, 341-
346

Eophyton, 251

Eozoon, 243

Fairy stones, 143

Faults in strata, 203

Fauna of silurian period, 259
of the permian, 297
of the cretaceous period, 324

Felsite, 169

Felspars, 136

Ferns of the carboniferous period,
282

Fire-clay, 158

Fishes of the silurian period, 265
of the devonian period,
in the carboniferous period,

291

of the permian period, 299
of the triassic period, 306
in the Jurassic period, 315
of the cretaceous period, 331

Flint, 106

Flood-plain of rivers, 40

Flora of the triassic period, 304
of the Jurassic period, 310

Flourine, 125

Flourides, 142

Foot-prints, 184

Forests, submerged, 11C

Fragmental rocks, 146

Fresh-water lakes, how formed, 44

Frost, changes on earth's surface
by, 13

Fossil remains, 220

Fossilisation, 223

Fossils, how indicative of geo-
graphic change, 226



INDEX



385



Gasteropods in cambrian period,

255

of the silurian period, 264
in the carboniferous period,
291

Geographic changes indicated by
fossils, 220

Geologic chronology, shown by
fossils, 228

Geological record, table of, 240, 241

Geology, nature of its inquiries, 5
the study of earth's history, 9

Glacial period, 364

Glaciers and ice-sheets, 65-71

Glassy rocks, 149

Glen Roy, parallel roads of, 46

Globe, earliest condition of, 234

Globigerina ooze, 88

Gneiss, 176

Granite, 170

Gravel, 155

Graywacke, 157

Great Salt Lake, 50

Greenland, fossils of, 326, 327

Ground-ice, 63

Guano, 166

Gypsum in lakes, 50

Gypsum, 140, 162

Hematite or specular iron, 133
Hornblende or amphibole, 137
Horse, ancestors of appear in the

eocene period, 344
Hydrogen, 124

Hydrozoa of silurian period, 260
Hydrozoon, 252

Ice-records, 63-71

Ice of rivers and lakes, changes

wrought by, 63
Iceland spar, 128
Ichthyosaurus or sea-lizard, 316
Iguanodon, last of the dinosaurs,

331

Infusorial earth, 85
Insects of the carboniferous period,

282, 285

Iron deposits in lakes, 49
Iron, 127
Ironstone, 163, 166

Joints in sedimentary rocks, 193
Jurassic period, 310-323

Kaolin, 158

Kimmeridgian stage of the Juras-
sic period, 322

Lamellibranchs, in cambrian pe-
riod, 255
in the carboniferous period,

290

in the triassic period. 305
in the Jurassic period, 313



Lakes, memorials left by, 44-50

filling up of, 45
Lake deposits, 47
Land, surface of, changing, 1-5

demolished by the sea, 72
Landslips, 52
Lava, varieties of, 100
Lias rocks, 320
Lignite or brown coal, 165
Limestone, 55, 160, 164
Limestone in the carboniferous

period, 278

Limonite, or brown\ iron ore, 134
Lizards first appear in the per-

mian period, 300

Lizards in the triassic period, 3o6
Loess, 159
Loess, 375
London, Roman remains in, 3

Magnesium, 126

Magnetite, 134

Mammals first appear in the trias-
sic period, 307
of the eocene period, 343
in the Jurassic period, 319

Mammoth, 369

Mammoth Cave, 56

Manganese, 127

Manganese oxides, 135

Mangrove-swamps, 85

Marble, 177

Marl in lakes, 48

Marcasite, 143

Mastodon, 352

Mechanical action of running

water, 27-30
of springs, 51

Megalosaurus, 317

Metals, 120, 125

Metamorphism in geology, 206

Metaloids, 120

Mesozoic periods, 302-337

Mica, 137

Mica-schist, 176

Minerals and elements, 119

Minerals, importance of in earth's
crust, 128-144

Mineral veins, 215

Miocene period, 350^-356

Mollusca of the silurian period,

264

of the devonian period, 275
in the carboniferous period.

285
of the eocene period, 342

Moraines, how formed, 65

Mosasaurus, 332

Mylonitic rocks, 152

Nature and use of fossils, 220, 233
Nebular hypothesis stated, 235
Necks, or volcanic vents, 215



386



INDEX



Neocomian stage of the Jurassic
period, 334

Neolithic period, 377

Niagara Falls, show power of ero-
sion, 34

Nitrogen, 125

Obsidian, 168

Old red sandstone period. See

Devonian Period.
Oligocene period, 346-349
Olivine, and serpentine rocks, 173
Olivine, 138
Oolitic rocks, 148
Ooze, 88
Organic remains, how preserved,

221

Orthoclase, 136
Orthoclase rocks, 168
Outcrop of strata, 197
Overlap, in geology, 190
Oxfordian stage of the Jurassic

period, 321

Oxides, abundance of, 132
Oxygen, importance of, 121
Oysters abuMant in the Jurassic

period, 313

Palaeolithic period, 374

Palaeozoic periods, 246-301

Peat, 165

Peat-bogs, 84

Peak cavern, 55

Peridot, 138

Perlitic rocks, 150

Permian rocks, how formed, 295-

301
Petrifaction of organic structure,

225

Petrifying springs, 60
Phosphorus, 124
Phosphates, 141
Phyllopod crustaceans of the silu-

rian period, 263
Pines appear in the Jurassic period,

311

Plagioclase, 136
Plants, geological records made by,

83-95

durable parts of, 222
of the devonian period, 269
of the carboniferous period,

282-284

of the permian period, 297
of the cretaceous period, 325
of the tertiary period, 339
of the eocene period, 341
Plesiosaurs, first appear in the tri-

assic period, 307
Plesiosaurus, 316
Pliocene period, 356-362
Pleistocene group, 363
Polyzoa in the carboniferous per-
iod, 289



Portlandian stage of the juraasic

period, 322

Post-tertiary periods, 363-381
Potassium, 126
Pot-holes, how made, 30
Porphyritic rocks, 150
Pre-cambrian period, 241, 242
Pterodactyl, 317
Purberkian stage of the Jurassic

period, 322
Pyrite, 143
Pyroxene, 138

Quarries, geological evidence of, 4
Quartz crystals, 122, 132
Quartzite, 177

Rain, a cause of change on earth's

surface, 14, 18, 20
Rain-prints, 184
Raised beaches, 116
Recent period, 371
Reptiles in the triassic period, 306
development of characteristic

of the Jurassic period, 31(5
of the cretaceous period, 331
River-action, records of, 35
River deltas, 78
River-terraces, 39
Rock-salt in lakes, 50
Rock-salt, 163

Rocks, geological evidence of, 119
Roman remains in London, 3
Rotation of earth in early ages,

237
Running water, in geological

changes, 24-43
Ripple marks, 183

Salt-lakes, formation of, 49

Sand, 156

Sand dunes, changes of, 21

Sandstone, 157

Saturation and dessication, influ-
ence of, 13

Schistose grit, 177

Schistose rocks, 174

Sea, geological records made by,
72-82

Sea-serpents of the cretaceous pe-
riod, 332

Sea-weeds, accumulations of, 86
as land makers, 87

Secondary era, see Mesozoic Pe-
riods.

Sedimentary rocks, 153, 159, 146,
179-207

Senonian stage of the Jurassic
period, 336

Serpentine, 139

Serpentine and olivine rocks, 173

Shale, 158

Shearing of strata, 199



INDEX



387



Sheets, of eruptive rocks, 211

Shell-marl, 164

Shell-banks, 87

Siderite, 146

Siliceous springs, 61

Silicates, 135

Silicon, importance of, 122

Silurian period, 258-268

Snow, geological effects of, 64

Sodium, 126

Soil beneath cities, nature of, 3

Soil and subsoil, changes in, 16-22

Sphagnum, or bog moss, growth of,
85

Spherulitic rocks, 150

Springs, geological records of, 51-
62

Stalactites, how formed, 57

Stalagmites, how formed, 57

Stegosaurus, 318

Stone implements found under
London, 3

Stones transported by rivers, 38

Storm beaches, 79

Stratification, 180

Strike of strata, 196

Strata, alternation of, 187

chronological value of, 188
conformability of, 190

Subsidence of land, 278-280

Subsidence, proofs of, 189

Sulphates, 140

Sulphides, 143

Sulphur, 124

Sun-cracks, 184

Syenite, 169



Temperature, influence of changes
in, 13

Tertiary periods, 338-362

Titanic iron, 135

Trachyte, 169

Transporting power of running
water, 25

Transportation by glaciers, 65

Travertine, 59

Trilobites in cambrian period, 254
of the silurian period, 263
in the carboniferous period.

288
of the devonian period, 273

Triassic period, 302-310

Turonian stage of the Jurassic pe-
riod, 335

Upheaval and subsidence, 115

Veins and dykes, 214

Vesicular rocks, 151

Volcanic ash, 159
dykes, 112
products, 100-107
vents and fissures, 107

Volcanoes, importance of their
study, 7

Volcanoes and earthquakes, 96-114

Water, running, in geological
changes, 24-43

Weathering, influence of, 11-14

Wind, effect of on earth's sur-
face, 18

Winding of streams, how formed.
32



Talus, how formed, 19



Zeolites, 136






Online LibraryArchibald GeikieGeology → online text (page 31 of 31)