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Stress & Strain Structural geology & Plate tectonics.

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Presentation on theme: "Stress & Strain Structural geology & Plate tectonics."— Presentation transcript:

1 Stress & Strain Structural geology & Plate tectonics

2 Stress & Strain Applied force & deformation

3 Increasing strain with increasing stress

4 Rock deformation Key factors: Composition Temperature Stress duration Stress rate

5 Plate choctonics

6 Joints (tectonic) Brittle fracturing with little displacement

7 Joints (igneous) Contraction during cooling

8 Faults Brittle deformation with displacement Extension = 'normal' faults

9 Faults Compression = 'reverse' faults

10 Strike-slip faults San Andreas Fault, western USA Lateral movement

11 Ductile (plastic) deformation = Folding Mainly at depths >10 km, and T >300° C King Oscar Fjord, Greenland

12 Low-grade strain ‘Delabole butterflies’, Cornwall Fossil rich mudstone strained into slate Tyne & Wear Museums University of Exeter

13 High-grade strain Gneiss, Aguanish, Quebec

14 Mapping out the structures

15 The Theory of Plate Tectonics Old Lost Seas

16 Earth Puzzles * Fossil distributions * Continental margins * Volcanoes and earthquakes * Compositions

17 W is for Walcott

18 W is for Wegener * Continental drift * Gondwanaland & Pangaea = “near-universal and near-perpetual ridicule”

19 W is for Wilson Geophysicist Hotspots 'Proto-Atlantic’ Wilson Cycles

20 Plate tectonics

21 Earth interior

22 Terms Crust (chemical) = mafic-felsic rocks overlying ultramafic mantle (0-70 km thick) Lithosphere (mechanical) = brittle upper layers (crust + upper mantle) (0-300 km thick) Aesthenosphere (mechanical) = ductile part of upper mantle

23 How thick do you like your crust?

24 Making the Earth move Mantle convection

25 Seismology and the Moho Andrija Mohorovicic, seismologist

26 Seismology and the Moho Base of brittle lithosphere at ~1300° C

27 Thin, young oceans

28 Geomagnetic oceans Symmetric bands of magnetized minerals in ocean crust

29 Spreading ridges Oceanic crust formed by extension; Upwelling of mafic magma

30 Spreading ridges

31 Convergence Oceanic-continental (e.g. Andes)

32 Convergence Oceanic-oceanic (e.g. Japan) Continental-continental (e.g. Himalayas)

33 The full picture Ocean birth to death = Wilson Cycle

34 Iapetus - the Old Lost Sea

35 The Ordovician Atlantic

36 Iapetus in Wales The Welsh Basin Palaeozoic marine mudstones (Many now slate)

37 Iapetus in Scotland Glens and highlands

38 Caledonian orogeny

39 Old Lost Sea in Newfoundland An Iapetan slice of upper mantle

40 W is for Williams Appalachians-Caledonides Gros Morne National Park

41 Avalonia A micro-continent of the Iapetus Ocean Colony of Avalon, Newfoundland

42 Iapetus (1)

43 Iapetus (2)

44 Iapetus (3)

45 The Iapetus of Man Niarbyl Fault, nr Dalby, south-west Isle of Man

46 The Iapetus of Man NORTH AMERICA (Laurentia) EUROPE(Avalonia)

47 Next week


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