Ch. 02 Flashcards
(132 cards)
1
Q
Which rock group among igneous, sedimentary, and metamorphic is emphasized for studying the Earth’s history
A
Sedimentary rocks.
2
Q
How are sedimentary rocks described in terms of deposition?
A
Deposited in layers, with the youngest at the top.
3
Q
What crucial elements do sedimentary rocks contain that aid in studying past geological times?
A
Fossils, representing the life of past geological times.
4
Q
According to James Hutton’s principle of uniformitarianism, what is the key to understanding events recorded in rocks?
A
The present-day activities of geological agents.
5
Q
Briefly explain the principle of uniformitarianism.
A
‘The present is the key to the past’; events recorded in rocks can be understood by reference to present-day geological activities.
6
Q
Who is regarded as the founder of modern geology and who introduced the principle of uniformitarianism?
A
James Hutton.
7
Q
What term did Fuchsel introduce for a layer of sedimentary rock?
A
Stratum.
8
Q
What geological principle suggests that in an undisturbed series of beds, the bottom stratum is the oldest, and successively younger beds lie upon it?
A
Order of superposition.
9
Q
Who noted that layers of rock could be traced across the country and described them as resembling ‘superimposed layers of bread and butter’?
A
William Smith.
10
Q
What term is used to describe layers of rock that can be traced across country with the same order of superposition?
A
Strata.
11
Q
Explain the concept of ‘way-up’ in determining the orientation of beds in a sequence.
A
It involves observing internal structures, such as current-bedding, graded-bedding, included fragments, and fossils.
12
Q
What is current-bedding, and how does it appear in sedimentary rocks?
A
Tops of beds are truncated by younger beds due to current action.
13
Q
Describe graded-bedding and how it forms in sedimentary rocks.
A
Grains of different sizes settle at different velocities, with coarse grains at the bottom grading to finer grains at the top.
14
Q
What are included fragments, and how do they contribute to understanding the sequence of beds?
A
Inclusions of rock, like pebbles, derived from an older formation; they indicate relative age.
15
Q
How do fossils help in determining the relative age of strata?
A
Fossils found in strata provide clues about their relative age.
16
Q
In the idea of superposition, what does the bottom stratum in an undisturbed series of beds represent?
A
The oldest or earliest formed.
17
Q
What does the stratigraphical column represent in geological terms?
A
The sequence of rocks formed during geological time, listed in order of age.
18
Q
Where are the oldest rocks placed in the stratigraphical column, and where are the youngest rocks found?
A
Oldest rocks are at the base, and the youngest rocks are at the top.
19
Q
What are Periods in the stratigraphical column, and how are they named?
A
Periods are groupings of rocks named after areas or characteristics, such as the Cambrian (after Cambria, Wales) and the Carboniferous (referring to coal-bearing rocks).
20
Q
Explain how the Carboniferous and Cretaceous Periods are named.
A
Carboniferous refers to coal-bearing rocks, and Cretaceous refers to rocks including chalk (Latin creta).
21
Q
What are some examples of Periods named after areas where they were first studied?
A
Cambrian (after Cambria, Wales), Ordovician, and Silurian (after the territory of the Ordovices and the Silures, ancient tribes of Wales).
22
Q
What is the Permian named after, and where is it located?
A
Named after Perm in Russia.
23
Q
From what source are the absolute ages of many rocks derived, according to the text?
A
Radiometric dating.
24
Q
What is an unconformity, and what does it represent in geological terms?
A
An unconformity is a junction where one series of strata lies upon an older series with a separation surface between them. It represents an interval of time when deposition ceased, denudation occurred, and uplift took place.
25
Explain the term "orogeny" and its relation to geological time.
Orogeny refers to mountain-building activity. Major periods of mountain building are indicated in geological time.
26
What are fold-mountain belts, and how are they characterized after denudation?
Fold-mountain belts are areas where rocks have been thrown into complex folds. After denudation, they are zones of instability in the crust, or mobile-belts.
27
Define epeirogenic and orogenic movements, and how are they related to the lithosphere plates?
Epeirogenic movements involve changes in the position of continents and are relatively stable. Orogenic movements are related to mountain-building. Both are linked to changes in the relative positions of plates of the lithosphere
28
What is a large, elongate trough of subsidence where marine sediments accumulate over a long period?
Geosyncline.
29
Where are marine sediments deposited on the subsiding floor of the geosyncline?
On the subsiding floor of the trough.
30
During the downwarping of the geosyncline, what type of sediment is poured into the trough after the marine sediments?
Coarser sediment derived from the rapid weathering of nearby land areas.
31
What process adds igneous material to the accumulation in the geosyncline?
Volcanic activity.
32
What happens to the basement of the geosyncline as volcanic activity occurs?
The basement is dragged down into hotter depths.
33
What geological process follows the accumulation of sediment in the geosyncline, involving the crumpling and breaking of the contents?
Thrusting.
34
What occurs to the sides of the geosyncline as the thrusts take place?
The sides begin to move together and are heaved up to form a range of mountains on the site of the earlier trough.
35
In summary, what is the entire process in the geosyncline, leading to the formation of mountain ranges?
Deposition of marine sediments, addition of coarser sediment, volcanic activity, dragging of the basement, sediment concentration, and finally, thrusting and mountain formation.
36
What does the ancient rock assemblage of the Precambrian represent in terms of Earth's history?
3600 million years, comprising all rocks older than the Cambrian.
37
How would you illustrate the immense duration of Precambrian time in relation to the Earth's age?
If the Earth's age is 1 hour, then the Precambrian would occupy 52 minutes.
38
What types of rocks largely make up the Precambrian, including virtually undisturbed sedimentary deposits?
Igneous and metamorphic rocks, with virtually undisturbed sedimentary deposits in places.
39
Where can sedimentary structures similar to those formed in present-day deposits be observed within Precambrian sediments?
In Canada, Norway, South Africa, and Australia.
40
What does the presence of glacial deposits in Canada, Norway, South Africa, and Australia demonstrate about Precambrian times?
Glacial conditions developed more than once in Precambrian times.
41
Give an example of preserved varved clays in Finland and their deposition time.
Varved clays, now metamorphosed, were deposited 2800 million years ago in a glacial lake in Finland.
42
How were many of the metamorphic gneisses formed, and where are they now visible?
They were formed at depth below the surface under high temperature and pressure, and they are now visible in areas where uplift and erosion have exposed once deeply buried rocks.
43
What are the large continental areas where Precambrian rocks are close to the present-day surface called?
Shields.
44
What are shields, in terms of geological stability and orogenic folding?
Shields are old, stable parts of present continents that have not been subjected to orogenic folding since the end of Precambrian times.
45
Where are diamonds mined from the Precambrian?
Kimberley, South Africa, and in Brazil.
46
What is the oldest group of rocks in N.W. Scotland, named after the Hebridean island of Lewis?
Lewisian rocks.
47
What is the age range of the Lewisian rocks in N.W. Scotland?
3000 to 1700 million years old.
48
How many periods of mountain building have deformed the Lewisian rocks, and what types of rocks do they consist of?
Deformed by at least two periods of mountain building, consisting of metamorphic rocks cut by igneous intrusions (dykes).
49
Which series overlies the Lewisian rocks unconformably in N.W. Scotland, and where is it named after?
Torridonian series, named after Loch Torridon.
50
Describe the Torridonian sediments in N.W. Scotland.
Answer: They consist of brown sandstones with subordinate shales and are 800 million years old.
51
What geological feature fills hollows in the Precambrian topography of the Lewisian land surface in N.W. Scotland?
Boulder beds at the base of the Torridonian formation.
52
What group, known as Moinian, comprises upper Precambrian granulites and schists in N.W. Scotland?
The Moinian group.
53
Where is the Moinian group located in N.W. Scotland?
East of the Moine Thrust-zone.
54
What significant geological feature has driven slices of Precambrian rock over younger Cambrian strata in N.W. Scotland?
Large thrusts, including the Moine thrust.
55
What ancient mountains were built during orogenic deformation in N.W. Scotland, occurring 150 million years later than the thrusts?
The Caledonides.
56
Where are Precambrian rocks in Scotland believed to be closely related to rocks of similar age, and what areas are mentioned?
Closely related to rocks in the Appalachians, Newfoundland, and Greenland.
57
What is believed about the original location of the areas containing Precambrian rocks in Scotland, Appalachians, Newfoundland, and Greenland?
It is believed these areas were joined as one continent at some time during the Precambrian, although their present location does not represent their original location.
58
What percentage of geological history is represented by the Phanerozoic?
The last 13 percent.
59
What distinguishes the Phanerozoic era?
The development of life.
60
What are the remains of organisms called, and what is deduced from studying them?
Fossils; the history of Earth life is deduced from the fossil record.
61
Which three geological periods make up the Older Palaeozoic rocks?
Cambrian, Ordovician, and Silurian.
62
How long do the Older Palaeozoic rocks, including the Cambrian, Ordovician, and Silurian, cover?
A span of some 182 million years.
63
What does the Older Palaeozoic record, in terms of sedimentation?
It records a long period of marine sedimentation in the oceans between the continents of Precambrian rock and in the shelf seas along their margins.
64
How many continents are believed to have existed during the Older Palaeozoic, and can you name three of them?
Four continents are believed to have existed. Examples include the shield of N. America and Greenland, the shields of Scandinavia and the Baltic, and the shields of Russia and Asia.
65
What geological processes occurred during the Older Palaeozoic that led to the formation of extensive mountain ranges?
Movement of oceanic plates against continents and collisions between continents
66
Name the extensive mountain range formed along the edge of the continent comprised of the S. American, African, Antarctic, and Australasian plates during the Older Palaeozoic.
Samfrau fold belt.
67
Which mountain range resulted from the collision between the Baltic and Russian shields during the Older Palaeozoic?
The Urals.
68
Between which continents were the Caledonides formed during the Older Palaeozoic?
Between N. America and Scandinavia.
69
What is the ancient range formed by the Caledonides during the Older Palaeozoic, and where are its remnants found?
The Caledonides; remnants are found in Scandinavia, the northern part of the British Isles, Newfoundland, and the Appalachians.
70
What are the remains of organisms with hard skeletons called?
Fossils.
71
What were trilobites, and where did they live?
Trilobites had a segmented outer skeleton consisting of a head, thorax, and tail; they lived in the mud of the sea floor.
72
Describe the outer shell of brachiopods.
Brachiopods had a bivalve shell, with two parts hinged together to form a chamber in which the animal lived.
73
What are graptolites, and why was their distribution greater than that of trilobites and brachiopods?
Graptolites were small floating organisms comprising colonies of simple hydrozoa attached to a stem, resembling a quill pen. Their distribution was greater because they could float, unlike trilobites and brachiopods restricted to the sea floor.
74
What is the Samfrau fold belt?
The Samfrau fold belt is an extensive mountain range formed during the Older Palaeozoic.
75
How did fossils in the shelf sea deposits of Scotland and N. America indicate the movement of continents during the Older Palaeozoic?
Fossils indicated that Scotland and N. America were on the northern margin of the ocean, while England and Wales were on the southern margin. Similar fossils in Scotland and N. America suggest their proximity, which changed over time due to subduction.
76
What acted as a barrier to life forms between the northern and southern margins of the ocean during the Older Palaeozoic?
The deep oceanic waters between the two continents acted as a barrier.
77
Why were graptolites excellent fossils for providing stratigraphic correlation?
Graptolites could float, allowing them to cross the ocean, making them useful for correlating sedimentary layers.
78
What geological processes led to the closure of the ocean between continents during the end of the Older Palaeozoic?
Intense mountain-building movements and subduction led to the closure of the ocean.
79
Describe the sedimentation patterns during the end of the Older Palaeozoic.
Shallow water Cambrian sediments were followed by deep-sea Ordovician sediments scraped off the oceanic plate. Silurian sediments characterized shallow water deposits when the constricted ocean was almost full of sediment.
80
What mountain range resulted from intense mountain-building movements during the end of the Silurian period?
The Caledonides.
81
Which continents were located to the north and south of the Caledonides during the Older Palaeozoic?
To the north, the continent of Laurasia, including N. America, Greenland, Scandinavia, Baltic, Russia, and part of Asia. To the south, the southern continent of Gondwana, including S. America, Africa, Antarctica, India, and Australasia.
82
Which three periods make up the Newer Palaeozoic?
Devonian, Carboniferous, and Permian.
83
What geological event does the Newer Palaeozoic record?
The gradual northerly drift of Gondwana and its collision with Laurasia to produce the Hercynian fold belt of N. America and Europe.
84
What are the continental sediments formed during the Devonian referred to as, and what caused their accumulation?
The Old Red Sandstone. Accumulation was caused by denudation of great mountain chains in Laurasia, resulting in flash floods, red sands, breccias, and finer materials in lakes and deltas.
85
What marked the beginning of the Carboniferous, and what geological process is believed to have caused it?
A marine transgression, believed to represent downwarping of a continental margin caused by subduction of an oceanic plate beneath it.
86
What geological event occurred by the end of the Carboniferous, and what is the resulting continent called?
The Hercynian orogeny occurred, and Laurasia and Gondwana were joined to form one huge continent called Pangaea.
87
What major division marks the end of the Palaeozoic Era, and what was happening in Gondwana during this time?
The Hercynian orogeny marks the end of the Palaeozoic Era. In Gondwana, there was an ice age known as the Gondwana glaciation, as recorded by the Dwyka Conglomerate.
88
What deposits formed in the tropics during the Permian, and why did they not permit aquatic life to flourish?
Red desert sands of the Permian, derived from denudation of the Hercynian Mountains. Saline conditions in the tropical gulfs and embayments did not permit aquatic life to flourish, leading to many species becoming extinct.
89
Where do the Permian marine sediments that provide the standard sequence for the period come from?
The Russian province of Perm provides the standard marine sequence for the Permian period.
90
What is abundant in the Old Red Sandstone and continued its line to the present day?
Fish.
91
Where do brachiopods occur in abundance during the Newer Palaeozoic?
In the Carboniferous Limestone.
92
What type of environment do the presence of corals in the Carboniferous suggest?
Clear, warm, and shallow seas, resembling those in the south Pacific at the present day.
93
What structures indicate the remains of ancient coral reefs in some limestones?
Mounds known as reef-knolls or bioherms.
94
What is the porous reef structure in Carboniferous seas capable of becoming, and what can it potentially store?
The porous reef structure can become a reservoir for oil and gas.
95
What features did crinoids have in the Newer Palaeozoic, and what supported the calcareous cup enclosing the body of the animal?
Crinoids had a calcareous cup enclosing the body, supported on a long stem made of disc-like ossicles.
96
How are cephalopods' shells in the Newer Palaeozoic structured, and what is a modern example similar to them?
Cephalopods had shells coiled in a flat spiral and divided into chambers by partitions. A modern example similar to them is the Nautilus.
97
What important group are goniatites, and how are they utilized in the Coal Measures?
Goniatites are an important group used as zone fossils in the Coal Measures. Particular species permit correlations between coal seams in different coalfields.
98
What are some remains found in coals during the Newer Palaeozoic, and what can the porous reef structure become?
Plants like Lepidodendron, pollens, and spore cases. The porous reef structure can become a reservoir for oil and gas.
99
What additional life forms developed during the Newer Palaeozoic?
All manner of insects and reptiles also developed.
100
What orogeny is associated with the Hercynian fold belt, and which mountain chain is named after this orogeny?
The Hercynian orogeny is associated with the Hercynian fold belt. The mountain chain named after this orogeny is the Harz Mountains of Germany.
101
What types of rocks were intruded into the root of the Hercynian mountain chain, and can you name an example of such an intrusion in S.W. England?
Granites were intruded into the root of the Hercynian mountain chain. An example is found in S.W. England.
102
What types of igneous rocks were intruded at higher levels in the crust during the Hercynian orogeny, and can you name an example, such as a prominent sill in northern England?
Basic igneous rocks, including dolerite, were intruded at higher levels in the crust during the Hercynian orogeny. An example is the Whin Sill, which underlies much of northern England.
103
Where did igneous activity reach the surface during the Hercynian orogeny, resulting in the eruption of basalt lavas and ash?
Igneous activity reached the surface in Scotland during the Hercynian orogeny, where many volcanoes were pouring forth basalt lavas and ash in the Midland Valley of Scotland.
104
What valuable minerals and deposits were created by the Hercynian orogeny along the fold belt?
Extensive deposits of valuable minerals and veins of lead, zinc, copper, and massive sulphide deposits were created by the Hercynian orogeny along the fold belt.
105
Which era comprises the Triassic, Jurassic, and Cretaceous periods, and what significant geological events mark the beginning and end of this era?
The Mesozoic era comprises the Triassic, Jurassic, and Cretaceous periods. The era begins with a single continent and ends with the division of this continent, separated by the oceanic ridge of the embryo Atlantic, drifting apart to east and west.
106
What is the term used to collectively refer to continental deposits of the Triassic that are indistinguishable from those of the Permian?
The term used is "Permo-Trias."
107
Which major ocean and fold belt are associated with the Mesozoic era, and what future mountain ranges were formed from sediments folded by the Alpine orogeny?
The Tethys ocean and the Cordillera fold belt are associated with the Mesozoic era. Sediments folded by the Alpine orogeny formed future mountain ranges, including the Alps and Himalayas.
108
During the Mesozoic, what marks the end of the Triassic in Europe, and what geological changes occur as Laurasia begins to split apart?
The end of the Triassic in Europe is marked by a shallow sea advancing slowly across southern Laurasia, depositing a thin sequence of clays (the Rhaetic). Laurasia begins to split apart, resulting in the opening of the Atlantic and great thicknesses of marine sediment accumulating.
109
What major geological activity occurred in western America during the Mesozoic, and what mountain-building orogeny is associated with the later stage in the history of Coridilleran mountain building?
In western America, during the Mesozoic, there was extensive geological activity, including active volcanism and immense intrusions of granite in the roots of the Andes. The later stage in the history of Coridilleran mountain building is called the Laramide orogeny.
110
Which era encompasses the last 65 million years of geological time and is divided into Tertiary and Quaternary periods?
Cenozoic Era.
111
What marks the beginning of the Mesozoic era, and what separates the two parts of the continent as the era ends?
The beginning of the Mesozoic era is marked by a single continent (Pangaea). The era ends with the division of the continent, separated by the oceanic ridge of the embryo Atlantic.
112
What type of shell did Ammonites have, and to which group of animals (modern-day equivalent) do they belong?
Ammonites had a coiled planar shell. They belong to the group of cephalopods.
113
What geological activity is associated with the later stage of Coridilleran mountain building during the Mesozoic, and what is the orogeny called?
The later stage of Coridilleran mountain building is associated with the Laramide orogeny.
114
Which lava flows are associated with the late Jurassic and early Cretaceous in the N. and S. Atlantic, and what landmasses are relics of these eruptions?
Fissure eruptions in the N. Atlantic created a big lava field, relics of which are seen today in Greenland, Iceland, the Faroes, Antrim, and the western islands of Scotland. In the S. Atlantic, similar fissure eruptions created the basalts of the Parana Basin in Brazil, with continuation found in southern Africa.
115
Which basin in Africa and India experienced basalt lava flows during the Cenozoic era, indicating the detachment of these shields from Africa?
Zambeze Basin of Africa and the Deccan of India experienced basalt lava flows, indicating the detachment of shields from Africa.
116
What event marks the culmination of the Alpine orogeny in the Cenozoic era, and what mountain ranges are produced as a result?
The compression of sediments during the Cenozoic era marks the culmination of the Alpine orogeny, producing the Alps and the Himalayas.
117
Which orogeny is the most recent to affect Europe, and what region demonstrates its ongoing seismicity?
Alpine orogeny; Mediterranean region.
118
When did the severe deformation of the crust along the arcuate fold belt of the Alps begin, and when did it reach its climax?
Began in the mid-Cretaceous and reached its climax in the Miocene.
119
What regions were affected by the Alpine orogeny in Europe, and what are the characteristic features of the fold belt?
Europe; gentle folds and basins in the north, complex folding in the south. Features include overthrusting, metamorphism, and intrusion of granite.
120
Where does the Alpine fold belt extend beyond Europe, and which regions does it merge with?
Extends into Turkey, Iran, Afghanistan, Tibet, Nepal, Burma, Thailand, Sumatra, and Java.
121
What sustained the orogenic movements along the western margin of America during the Cenozoic era, and what mountain range in N. America formed during the Laramide phase of the orogeny?
Continued western drift of the American plates; Rocky Mountains.
122
What type of deposits characterizes the Quaternary period, and how are they described in comparison to harder, more solid rocks?
Quaternary deposits are widespread and diverse, often described as 'Drift.'
123
Which fault system developed in N. America during the Cenozoic, and what was happening to the western Andes in S. America during the same period?
San Andreas fault system; Western Andes continued to develop due to the subduction of the oceanic Nazca plate.
124
During which geological epoch did the Pleistocene glaciations occur, and what regions were covered by large ice sheets?
Pleistocene epoch; N. America, Greenland, N. Europe, Russia, and Antarctic.
125
What interrupted the Pleistocene glaciation, and what is the term used for the temporary improvement in climate with ice-front retreats?
Interglacial episodes; Inter-glacials.
126
List some areas affected by local ice-caps during the Pleistocene glaciations.
Many mountain ranges, such as the Alps.
127
Explain the isostatic effect during glaciation and the subsequent isostatic compensation during ice melting.
Glacial weight depresses land; melting leads to land re-elevation. Isostatic effect is locally variable.
128
How much has Scandinavia risen since the end of the Pleistocene Ice Age, and what is the estimated world-wide fall in sea level during glaciation?
Scandinavia rose by 215 m; world-wide fall in sea level estimated at almost 100 m.
129
What is the ongoing effect of the Pleistocene glaciation on sea levels, and what coastal features mark stages of isostatic and eustatic changes?
Ongoing sea level rise due to melting ice-caps. Raised platforms or 'beaches' mark stages of isostatic and eustatic changes.
130
What significant effects did the Pleistocene glaciation have on water levels, and what continues to happen as remaining ice-caps melt?
Locked water in ice-sheets causing world-wide fall in sea level; ongoing eustatic change as remaining ice-caps melt.
131
In the Cenozoic era, what does the fossil record within Tertiary sediments reveal about life, and what is the significance of microfossils of Protozoa?
Diversification of life; microfossils indicate water temperature and salinity, valuable in dating and correlating strata.
132
Why are microfossils of Protozoa particularly valuable in oil field drilling operations?
Extensive distribution, rapid evolution, and useful for identifying layers in drilled sediment.
