Making of a Land - Chapter 2

Illustrations chapter 2.

The illustrations can be downloaded in the gallery further down.

 

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 Chapter 02 - p. 24

The contours of the coastline on both sides of the Atlantic Ocean and the geological structures in Africa, South America, Europe and North America suggest that these continents once formed a single supercontinent. (Figur adapted from A. Marshak, 2005)

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Chapter 02 - p.25a 

A section through the Earths's interior, showing important boundaries and the distribution of density (d) and temperature. The Moho is a discontinuity where the density increases rapidly from the crust to the mantle. The crust is thickest beneath mountain chains on the continents because the rocks there are lighter than beneath the oceans.

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Chapter 02 - p. 25b

The Earth's interior, its shell-shaped structure and its main elements. mantle plumes are upwellings of molten rock from hot domains in the mantle which end in volcanoes on the Earth's surface. Cold plates of lithosphere which sink beneath lighter plates may go all the way down to the base of the mantle before they disintegrate.

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Chapter 02 - p. 26a

Peeping into the centre of the Earth. The Mid-Atlantic Ridge with its longitudinal fissures and canyons crosses Iceland from south to the north. At Thingvellir in southern Iceland, the site of the former Icelandic Althing, the Earth's crust is still spreading along deep canyons that cut the terrain. Lake Thingvalla, in the background, contains active volcanoes. (Phtot: J.P. Nystuen)

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Chapter 02 - p. 26b

The magnetic anomaly stripes reflect the orientation of the Earth's magnetic field when the rocks solidify along the mid-ocean ridges. Grey stripes show normal orientation and white stripes reverse orientation.

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Chapter 02 - p. 26c

The magnetic anomaly stripes reflect the orientation of the Earth's magnetic field when the rocks solidify along the mid-ocean ridges. Grey stripes show normal orientation and white stripes reverse orientation.

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Chapter 02 - p. 27a

The main features of plate tectonics. New oceanic crust is formed along mid-ocean ridges, while old, heavy crust sinks beneath lighter crust in subduction zones where mountain chains form. Ocean-floor sediments are subducted together with the oceanic plate or are scraped off in accretionary wedges. Crustal stresses trigger earthquakes along the plate boundaries.

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Chapter 02 - p. 27b

Present-day lithospheric plates. The plates drift apart along divergent boundaries where new ocean-floor crust forms, and meet each other along convergent boundaries where mountains form. Transform faults are transverse fractures along divergent boundaries where the mid-ocean ridges are apparantly fragmented and pushed aside.

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Chapter 02 - p. 28a

The Earth as a magnet. In our  time, when polarisation is normal, the magnetic dipole points south, whereas it points north in periods with reverse polarisation (lowermost left). Basalts of known age have preserved the print of the magnetic dipoles from the named times with normal and reverse polarity (middle left). A magnetic time scale (right) is used to determine the age of corresponding magnetic anomalies in ocean-floor crust (uppermost left). (Figur adapted from S. Marshak)

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Chapter 02 - p. 28b

The Earth as a magnet. In our  time, when polarisation is normal, the magnetic dipole points south, whereas it points north in periods with reverse polarisation (lowermost left). Basalts of known age have preserved the print of the magnetic dipoles from the named times with normal and reverse polarity (middle left). A magnetic time scale (right) is used to determine the age of corresponding magnetic anomalies in ocean-floor crust (uppermost left). (Figur adapted from S. Marshak)

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Chapter 02 - p. 28c

Magnetisation of lava. When the temperature in a lava rock drops below about 450oC, the dipoles in all magnetised minerals become oriented parallel with the Earth's magnetic dipole. An internal print is preserved of the polarity, direction and angle of the magnetic lines at the place where the lava was formed relative to the Earth's surface. (Figur adapted from P.J. Wyllie)

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Chapter 02 - p. 28d

The Earth as a magnet. In our  time, when polarisation is normal, the magnetic dipole points south, whereas it points north in periods with reverse polarisation (lowermost left). Basalts of known age have preserved the print of the magnetic dipoles from the named times with normal and reverse polarity (middle left). A magnetic time scale (right) is used to determine the age of corresponding magnetic anomalies in ocean-floor crust (uppermost left). (Figur adapted from S. Marshak)

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Chapter 02 - p. 29

The plate tectonic cycle from the break-up of an old continent to the formation of a new one.

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Chapter 02 - p. 30

At Bitihorn in the outer part of the Jotunheimen Mountains in  Valdres, south-central Norway, Precambrian gabbro was thrust over younger Precambrian sandstones that form the bedrock in the ridge in the foreground. The thrusting took place when two plates collided during the Caledonian orogeny at the end of the Silurian about 145 million years ago.  (Photo: I.Bryhni)

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Chapter 02 - p. 32

Two quartz crystals (rock crystals) coated with antase crystals. Hardangervidda. (Natural History Museum Collection, photo: P. Aas)

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Chapter 02 - p. 33

Classification of plutonic rocks. (Adapted from A.L. Streckeiesen and R.W. Le Maitre)

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Chapter 02 - p. 34

(Photo1 og 2: I. Bryhni. Photo 3: B.T. Larsen)

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Chapter 02 - p. 35

Plutonic, hypabyssal and volcanic igneous rocks.

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Chapter 02 - p. 36a

Faults are fractures in the Earth's crust along which displacement has occurred. The relative movement between the crustal blocks forms the basis for distinguishing different kinds of faults, as shown in a) to g).

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Chapter 02 - s. 36b

Faults are fractures in the Earth's crust along which displacement has occurred. The relative movement between the crustal blocks forms the basis for distinguishing different kinds of faults, as shown in a) to g).

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Chapter 02 - s. 36c

Faults are fractures in the Earth's crust along which displacement has occurred. The relative movement between the crustal blocks forms the basis for distinguishing different kinds of faults, as shown in a) to g).

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Chapter 02 - s. 36d

Faults are fractures in the Earth's crust along which displacement has occurred. The relative movement between the crustal blocks forms the basis for distinguishing different kinds of faults, as shown in a) to g).

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Chapter 02 - s. 36e

Faults are fractures in the Earth's crust along which displacement has occurred. The relative movement between the crustal blocks forms the basis for distinguishing different kinds of faults, as shown in a) to g).

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Chapter 02 - s. 36f

Faults are fractures in the Earth's crust along which displacement has occurred. The relative movement between the crustal blocks forms the basis for distinguishing different kinds of faults, as shown in a) to g).

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Chapter 02 - s. 36g

Faults are fractures in the Earth's crust along which displacement has occurred. The relative movement between the crustal blocks forms the basis for distinguishing different kinds of faults, as shown in a) to g).

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Chapter 02 - p. 37

A. Anticlines are folds that bend the beds upwards; synclines bend them downwards.
B. A folded succession shows a characteristic pattern on the geological map. The orientation of the beds is indicated by symbols for strike and dip and the direction of the fold axes.

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Chapter 02 - p. 38

Nappes and thrusts sheets in a mountain chain. Beyond the mountain chain, a sediementary succession remains undisturbed on its original basement. Towards the mountain chain, the strata are folded and thrust together in thrust sheets and nappes, the further into the chain you come, the further the nappe rocks have been thrust.

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Chapter 02 - p. 39

Climbing Besseggen, a well-known ridge in the Jotunheimen Mountains in south-central Norway. Gjende is the lake on the left and Bessvatnet that on the right. Gjende was excavated by a glacier following a fault zone in easily eroded bedrock. The Gabbro on Besseggen is traversed by bands of hard crush rock called mylonite, which have fortified the ridge, preventing it from being completely worn down by the glacial erosion that otherwise marks the landforms in the Jotunheimen Mountains. (Photo: J.P. Nystuen)

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Chapter 02 - p. 39

The small picture shows the appearance of the mylonite at close quarters. The layer with thin, dark and light bands is a result of locally intense shearing and recrystallisation under plastic conditions to produce a very fine-grained, extremely deformed rock. (Photo: J.P. Nystuen)

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Chapter 02 - p. 41

Acidic water flowing over marble has produced deep flutes because the carbonate minerals in the rock have dissolved. Fræna, Møre og Romsdalen. (Photo: I.Bryhni)

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Chapter 02 - p. 45

The main types of sedimentary basins, as they are formed in a plate tectonic context.

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Chapter 02 - p. 48

This sandstone originated as sand in a shallow Early Cretaceous sea on Spitsbergen. The geologist is filling in a log recording observations on the thickness, grain size and sedimentary struktures. The compass is used to measure the orientation and directions in the sandstone beds and the geology hammer to collect samples. (Photo:E.Tallaksen)

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Chapter 02 - p. 49

Classification of sediments and sedimentary rocks according to grain size. (Figure from S. Gjelle and E. Sigmond)

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Chapter 02 - p. 51

Pale rose-coloured gneiss and black amphibolite, both transected by granitic veins, were formed deep in the crust in a fold belt about 1000 million years ago. The Precambrian basement near Drøbak, east of Oslofjorden. (Photo: J.P. Nystuen)

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Chapter 02 - p. 55

Geological map, part ov the Asker sheet, 1814 I, scale1:50 000. (J. Naterstad et.al., NGU)

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Chapter 02 - p. 56a

Relative age in a succession.
a) A succession is deposited, in part as delta sand and silty clay in the sea,
b) the succession is folded and eroded; valleys and ridges reflect the varying hardness of the beds,
c) the mountains are worn down to a peneplain over which the sea has flooded, and
d) a new succession is deposited.

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Chapter 02 - p. 56b

Stratigraphical division.

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Chapter 02 - p. 57

Relative age in part of the Earth's crust. Order of age is shown by boundary relations between rocks, deposits, struktures and landforms. Younger layers are deposited above older ones, folds are formed after the beds are deposited, younger intrusive rocks cut through older rocks, erosion surfaces cut down into underlying beds, and so on. Find the order of the geological development!

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Chapter 02 - p. 58a

Baltazar Mathias Keilhau (1797-1858), Founder of geology in Norway.

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Chapter 02 - p. 58b

Theodor Kjerulf (1825-1888)

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Chapter 02 - p. 59

Division of successions into two types of sequences, between two erosion surfaces formed by a fall in sea level and between two surfaces formed when the sea transgressed the land. Surfaces with the same age cut through the boundaries of the various sedimentary strata. It is important to correlate - establish a mutual connection between - the successions in the wells that have been drilled through succession.

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Chapter 02 - p. 60

The geological time scale of the Earth. 2008 versieon of ICS's International stratigraphic chart. (Adapted from F.Gradstein et.al.)

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Chap. 02 - s. 61

Permafrost is widespread in Svalbard right down to sea level. The ring-shaped accumulations of stones on Vardeborgsletta on the south side of outer Isfjord on Spitsbergen are formed by stoned being pressed up from the permafrost in the ground beneath, and sorted (patterned ground). The stones were originally shore pebbles, and are clean and light coloured because they have been buried in the ground. (Photo:O.Salvigsen)

 

 

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