QUESTIONS
TO
ELEMENTS OF GEOLOGY
QUESTIONS.
CHAPTER I.
SECTION I.
How many elementary substances are known?
In what combinations is oxygen found? What proportion of the earth’s crust consists of it?
In what combinations does hydrogen occur? Nitrogen? Carbon? Sulphur? Chlorine? Fluorine? Iron? Manganese?
How does silicium occur? Aluminium? Potassium? Sodium? Calcium? Magnesium?
How are these elementary substances classified? (Silicium, or silicon, has but a doubtful claim to be regarded as metallic.)
SECTION II.
What is a simple mineral? How many are known?
What are the physical properties of quartz? How are the several varieties distinguished?
What are the physical properties of felspar? Mica? Hornblende? How are its varieties distinguished? Augite? Hypersthene? Talc? How are its varieties distinguished? Serpentine? Carbonate of lime? Gypsum? Its varieties?
What other minerals are mentioned?
SECTION III.
Define the crust of the earth. Rocks.
What are the unstratified rocks?
What is the structure of granite?
How are the varieties distinguished?
What is the porphyritic structure?
Describe hypersthene rock.
What are volcanic rocks? Lava? Scoriæ? Pumice-stone?
How is the vesicular structure produced?
What are volcanic breccias? Volcanic grits?
What is the composition of the trappean rocks?
What is the amygdaloidal structure?
What are the three varieties of trappean rocks, and how are they distinguished?
Fig. 1.
Name the stratified rocks. Describe gneiss. Mica slate. Sandstone. Conglomerate. Greensand. Describe the varieties of limestone.
What is dolomite? Of what does clay consist? Clay slate? What modifications does clay slate present? What is diluvium?
CHAPTER II.
SECTION I.
What is the primary division of rocks?
Upon what principle are the unstratified rocks divided?
Upon what principle are the stratified rocks divided?
Why are the non-fossiliferous called metamorphic rocks?
Name the four classes of rocks.
SECTION II.
What is the most abundant plutonic rock?
How is its thickness ascertained?
What is its amount?
Where is it found?
What is its ordinary structure?
What peculiarity of structure facilitates the cleavage of granite?
Fig. 2.
The granitic masses are generally deep below the surface; in what other position does granite appear?
Fig. 3. Fig. 4.
In what classes of rocks are granite veins found?
Were they all produced at the same time?
How is this demonstrated?
What is the relative position of the older and newer granites?
What other plutonic rocks occur in considerable quantities?
SECTION III.
Of what do volcanic rocks consist?
In what states are they ejected?
What are the principal varieties of lava, and how are they distinguished?
Why is the basaltic lava the last to be ejected?
How is the age of the volcanic rocks determined?
What are the three divisions of the volcanic rocks, as dependent upon age?
What is the proportion of the volcanic to other rocks?
How many active volcanoes exist?
Describe the eruptions of Kilauea.
Describe the eruption in Iceland in 1783.
What are the dimensions of Mount Ætna, and how has it been produced?
How are the tertiary lavas known to be such?
Where have they been most studied?
What is the evidence that these rocks in France are volcanic?
Have these lavas been produced within the historic period?
Fig. 5.
Were they produced at an early period in the earth’s history?
Give the evidence that their activity was long-continued.
Fig. 6.
What is the form of the earlier volcanic rocks?
What circumstances distinguish the trappean from other volcanic rocks?
What are some of the prominent localities of the trappean rocks?
How do they occur in the islands west of Scotland?
How in the valley of the Connecticut river?
SECTION IV.
What is the lowest metamorphic rock?
Describe it.
How does mica slate differ from gneiss?
Is it well distinguished from argillaceous slate?
What is the third rock in the metamorphic series?
Why is it difficult to determine the upper limit of this series?
Why do the principal rocks of this series occur in the order here given?
What other rocks may take the place of these principal rocks?
Where do the metamorphic rocks occur?
What is their thickness and amount?
SECTION V.
How many systems of fossiliferous rocks are there, and what are they?
What other system is provisionally introduced?
What is its position?
Fig. 7.
Describe it.
What materials of value are obtained from this system?
Fig. 8.
What fossils does it contain?
In what localities is it found?
What explanation, in reference to these rocks, is given by those who deny that they constitute a distinct system?
Fig. 9. |
Fig. 10. |
In what respects does the State of New York present the best facilities for studying the Silurian system?
Describe the Champlain division.
Fig. 11.
The Ontario division.
The Helderberg division.
Fig. 12. |
Fig. 15. |
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Fig. 13. |
Fig. 14. |
Fig. 16. |
Describe the Erie division.
What are the fossils of this system?
Fig. 17.
Describe the Crinoidea.
The Cephalopoda, and the two forms.
Fig. 18.
The Trilobite.
What higher forms of animal life existed during the silurian period?
The geographical range of the system?
Of what does the Old Red Sandstone consist?
Describe its three divisions.
What are its fossils?
Fig. 19.
Describe the fishes of that period.
What was the peculiarity of the Pterichthys?
Of the Cephalaspis?
Where are the rocks of this system found?
How is the carboniferous system divided?
Describe the carboniferous limestone.
What ores are found in it?
Describe, its fossils.
Describe the millstone grit.
Of what do the coal measures consist?
How does the ironstone occur?
Describe the coal beds.
How is the continuity of the strata interrupted?
What variations from this general type occur in the formation?
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Fig. 20. |
Fig. 21. |
Describe the several varieties of coal.
How is the coal quarried?
Fig. 22.
What mineral springs occur in this formation?
To what uses is coal applied?
(The coal was deposited thousands of years ago, and has served no useful purpose, that we know of, till very recently. Its formation was planned and completed to meet a want which was not to be felt till the lapse of many ages. It is a notable instance of the wisdom and forethought, as well as of the benevolence, of God.) In what does this prospective arrangement consist? What are the character and position of the fossils of the coal measures?
Fig. 23. |
Fig. 25. |
Fig. 24. |
Fig. 26.
What are the four most abundant forms?
Describe the Stigmaria. The Sigillaria. The Lepidodendron. The Calamite.
Where are the beds of coal found?
What is the fourth formation of rocks?
Into what two portions is it divided?
Of what does the Permian portion consist?
The Trias?
What minerals are found in this formation?
What springs?
Fig. 27.
Fig. 28.
Fig. 29.
What fossils?
How are the fishes of the earlier and later portions distinguished?
What peculiarity of the red sandstones is mentioned?
By what kinds of animals were the tracks, which they contain, made?
Give localities of the new red sandstone.
What are the three divisions of the Oölitic system?
Fig. 31. |
Fig. 30. |
Fig. 32. |
Describe the Lias.
The Oölite.
The Wealden.
What are the general peculiarities of the system?
Fig. 33.
What are the fossil animals of the system?
By which class of fossil animals is the system characterized?
Fig. 34.
Describe the Ichthyosaurus. The Plesiosaurus. Pterodactyle. The Iguanodon.
Where is the system developed?
What are the divisions of the Cretaceous system?
How are the layers of chalk separated?
What is the geological position of the Neocomian system, and the greensand of this country?
What are the fossils of this system?
Fig. 35.
Fig. 36.
What the geographical range?
How are the tertiary deposits distinguished from the older formations?
Upon what principle is the tertiary system divided?
What are these divisions called, and what does each, name signify?
Fig. 37. |
Fig. 38. |
Fig. 39. |
Fig. 40. |
Fig. 41. Fig. 42.
Fig. 43.
In what portion of the tertiary period was the drift deposited
What is the geographical range of the drift?
Of what does it consist?
What is the latest tertiary deposit?
What are the fossils of the tertiary system?
Describe the Paleotherium. The Anoplotherium. The Megatherium. The Mastodon. The Mammoth.
What other animals belonged to this period?
Where are the tertiary deposits found?
What formations are regarded as recent?
What formations of this class are accessible?
What others are in progress?
What are the fossils of this formation?
SECTION VI.
What is a fossil?
In what ways are they preserved?
When is a fossil said to be mineralized?
Describe the process of mineralization.
How is it proved that the removal of the organic matter and substitution of mineral particles are simultaneous?
Were animals created before vegetables?
How is this shown?
At what period was the vegetable growth the greatest?
What forms of animal life were most abundant during the earlier periods?
What vertebrated animals belonged to these periods?
What advance is made in the new red sandstone period?
During what period do the mammalia first appear in abundance?
During what geological period was man created?
How are the footprints and skeletons of human beings hi solid rocks accounted for?
Why are not fossils distributed uniformly through all the formations, and through all the parts of each formation?
In what does the importance of fossils consist?
How are the fresh-water and marine formations distinguished?
What circumstances render it difficult to identify rocks of the same age in different localities?
How are formations identified?
Was the work of creation one of short duration?
What was the last work of creation of which we have any geological evidence?
Why may we presume that no more species will be created?
Do all the animal and vegetable species which have been created still exist?
Fig. 44.
Fig. 46. |
Fig. 45. |
Fig. 47. |
What causes are operating to destroy species?
SECTION VII.
How long has it been since the creation of the earth?
How does the amount of stratified rock indicate the great antiquity of the earth?
How does the stratification show the same thing?
What is the proof that the principal strata were deposited before the creation of man, and how does this fact bear upon the question of the antiquity of the earth?
Give the argument drawn from the successive creations and disappearance of animal and vegetable species.
The argument drawn from the amount of organic matter in the stratified rocks.
The argument from slow accumulation.
What is the general conclusion from these facts?
Why is this conclusion an important one?
What objection to it has been raised?
How is this objection answered?
What additional explanation is given?
CHAPTER III.
SECTION I.
What is the deepest geological change of which we have any knowledge?
What are the reasons for supposing that the lowest stratified rocks are undergoing fusion?
Why are the lowest stratified rocks regarded as of mechanical origin?
What changes have they undergone?
SECTION II.
In what state were the stratified rocks deposited? What change have they undergone in this respect? How is the fissile structure produced? How is the cleavage structure produced?
Fig. 48.
What is the third class of changes?
What do fractures at the surface become by the erosion of water? How are caverns formed?
Describe a vein of segregation. A dike. A mineral vein. What is a fault?
Were the inclined strata thus deposited?
How is it proved that they have taken the inclined position since they were deposited?
What is the direction of the dip?
What lines form the angle of inclination?
What is the outcrop of inclined strata? The strike?
Fig. 49.
Fig. 50.
Fig. 51.
Fig. 52.
Fig. 53.
Describe an anticlinal axis. A synclinal axis. A valley of elevation. A valley of subsidence.
Fig. 54.
Fig. 55.
Fig. 56.
When are strata unconformable?
What other disturbances have taken place in the strata?
When did these various disturbances take place?
How is it known that there has been no period of universal disturbance?
SECTION III.
How is it known that the mountains have been covered by the ocean?
Fig. 57.
Fig. 58.
Were the granitic ridges thus covered?
Has the level of the sea been, to any considerable extent, fluctuating?
How, then, have the rocks, of which the mountain masses consist, been covered by sea?
Give the evidence that different mountains were elevated at different times.
Has the process of upheaval been sudden or gradual?
How are the mountain valleys, which have the direction of the mountain ranges, been produced?
Fig. 59.
How is the existence of submarine mountains shown?
What is the movement by which continents are elevated?
State the evidence of the elevation of continents from the existence of elevated sea-beaches.
The evidence of the elevation of the coast of Maine.
The evidence of elevation from the existence of lakes.
From the geographical range of the older strata.
The evidence of the recent elevation of South America.
Of the rising of the north of Europe.
State the proof of subsidence from the occurrence of submerged forests.
Why are these changes but little observed?
Fig. 60.
What are the grounds for asserting that a change of level is taking place over a large area in the Pacific and Indian Oceans?
Fig. 61.
Fig. 62.
Fig. 63.
Fig. 64.
What is the present state of the coast of Greenland in this respect? Have the changes of level of the same place always been in the same direction?
Give the evidence of elevation and depression in South America. In Italy.
Fig. 65.
What general conclusion may we draw in respect to the stability of the earth’s surface?
To what extent can we ascertain the geography of past epochs?
What former relations of land and water are suggested as not improbable?
SECTION IV.
How can we estimate the denudation which the igneous rocks have suffered?
How do faults indicate the denudation of the stratified rocks?
How do valleys indicate denudations?
Describe the instance in Scotland.
What is the evidence of denudation in the Connecticut valley? How are valleys produced?
Fig. 66.
What is the condition of the surface rock in the colder portions of the temperate zones?
Fig. 67.
Fig. 68.
With what is the surface rock generally covered?
How are soils formed?
How may soils be improved?
What is necessary to render soils fertile?
SECTION V.
What means have we of judging of the climate of former periods?
What was the climate of the coal period?
What animal fossils indicate a former warm climate?
What evidence that Siberia once enjoyed a milder climate?
Do similar indications appear in the southern hemisphere?
When has the climate of the earth been most uniform?
Has the climate been growing gradually colder to the present time?
What is the evidence of a somewhat recent period of intense cold?
What recent local changes of climate are mentioned as having occurred?
SECTION VI.
State the general advantages of geological changes.
By what changes have the coal-beds and other stratified rocks become accessible?
What advantage from these elevating forces in reference to the granitic rocks?
Fig. 69.
How do these changes affect our means of knowing the structure of the earth?
Explain the origin of springs, wells, and artesian wells?
By what changes have the metallic ores become accessible?
In what light, then, are we to regard disturbances of geological structure?
CHAPTER IV.
What is the object of the preceding chapters?
How can we arrive at a knowledge of the causes which have produced geological phenomena?
Have geological causes always operated with the same intensity?
How are the means of forming correct geological theories increasing?
SECTION I.
How does oxygen become an agent in the disintegration of rocks?
How does carbonic acid operate in the disintegration of rocks?
What is the effect of moisture and rain?
What is the effect of variations of temperature?
What other atmospheric causes are mentioned?
How do these causes become important?
What are some of their effects?
SECTION II.
What are the changes which are to be referred to chemical agency?
Mention some of the disturbances which give rise to chemical changes.
What are the principal effects of chemical action?
How is the cleavage structure accounted for?
Fig. 70.
Fig. 71.
Mention instances which show that a cleavage may be established in a body in a solid state.
In it a crystalline arrangement of the particles of the mass?
What other divisional planes exist in rocks?
Mention instances of concretionary formations.
Why may not these concretions have been deposited as nodules?
How have these concretions been formed?
Mention instances of segregation without the concretionary structure.
How was the segregation in these instances effected?
How is the columnar structure produced?
What is the origin of the mineral veins which are first mentioned?
How is it shown that other veins are not injected?
How were these veins formed?
What is the force by which these molecular changes have been effected?
SECTION III.
In what ways are geological changes produced by human agency?
Of what are the organic remains, in rocks, the record?
What rocks contain organic materials in large quantity?
What is the most abundant organic product?
Explain the mode of growth of corals.
Give instances of extensive coral reefs.
What is the total amount of surface covered by the coral reefs?
SECTION IV.
What degree of importance is attached to water as a geological agent?
What are the sources of the sediment which water deposits?
Why is not the formation of the sedimentary rocks capable of being observed?
What is the first mode in which solid matter is taken up by water?
Why are the waters of the ocean saline?
What effect has the temperature of water in the solution of silex?
What effect has an alkaline condition of water?
Fig. 72.
What rock is soluble in water charged with carbonic acid?
Give an instance of limestone formation from such solutions.
How do rivers furnish sediment for the stratified rocks?
What determines the position of rapids in rivers?
What is the effect of waterfalls on the abrading action of rivers?
What is the peculiarity of rock at Niagara which has prevented the fall from becoming a succession of rapids?
What other circumstance increases the abrading action of rivers?
What is the principal source of the sediment which is transported by rivers?
What is the annual amount of sediment furnished by the Kennebec? The Merrimac? The Mississippi? The Ganges?
What is the general tendency of these abrading forces?
What is the effect of waves upon the coast, when it consists of unsolidified materials?
Describe their effect upon rocky coasts.
How is the encroachment upon such coasts shown?
Fig. 73.
What is the effect of waves of less power?
How are marine currents produced?
How are they increased by the evaporation of the torrid zone?
What are the most important marine currents?
Which class of currents have the greater depth?
Upon what does the power of deep currents depend?
How would the effect of these currents be increased by earthquakes?
Where will the effects of these currents be greatest?
Mention instances of these effects.