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Chapter 2 CHAPTER 2 THE EARTH IN SPACE AND TIME © Oxford University Press, 2008. All rights reserved. 1 Chapter 2 THE EARTH IN SPACE • Our galaxy – the Milky Way • Our solar system – the Sun and 9 planets • Earth’s elliptical orbit around the Sun • Equinoxes and solstices © Oxford University Press, 2008. All rights reserved. 1 Chapter 2 THE EARTH IN TIME • Meteorites and the Earth • The age of the Earth • The Earth’s atmosphere • Geological time scales • Life on Earth © Oxford University Press, 2008. All rights reserved. 1 Chapter 2 PROPERTIES OF THE EARTH • Determining the nature of the Earth • Density of the Earth • Magnetic fields and palaeomagnetism • Earthquakes • The Earth’s interior • The Earth’s crust © Oxford University Press, 2008. All rights reserved. 1 Chapter 2 PLATE TECTONICS • Continental crust • Oceanic crust • Lithospheric plates and ‘continental drift’ • Plate boundaries – Diverging plate boundaries – Transform fault boundaries – Convergent boundaries (collision, subduction) • Subduction boundaries and ocean trenches © Oxford University Press, 2008. All rights reserved. 1 Chapter 2 VOLCANOES • Present mainly along plate boundaries – Convergent, e.g. Pacific Rim – Divergent, e.g. sub-oceanic plates (spreading-ridge magmatism) – Within-plate volcanism : ‘hot spot’ mantle plumes (e.g. Hawaiian islands in Pacific Ocean plate) © Oxford University Press, 2008. All rights reserved. 1 Chapter 2 VOLCANOES – EFFECTS • Lava flows, pyroclastics – boulders, ash • Fine dust to 20 km into atmosphere • Gases and steam, including SO2, CO2 • Ash cones or extensive lava flows © Oxford University Press, 2008. All rights reserved. 1 Chapter 2 CONTINENTAL MARGINS • Plate boundaries and continental margins • Continental shelf • Exogenic forces and sedimentation on shelf • Sediment ‘starvation’ (large dams) leads to ocean encroachment © Oxford University Press, 2008. All rights reserved. 1 Chapter 2 ISOSTACY • Depth of compensation (asthenosphere), where materials exert similar pressure • Isostacy allows for reduction in stresses caused by variable loads including: – oceanic crusts thinner than continental crusts – mountain-building leads to uneven thickening of continental crusts – continental-scale ice caps – major sedimentation on continental margins, e.g. deltas • Isostatic readjustment and sea levels © Oxford University Press, 2008. All rights reserved. 1