Chapter 2 © Oxford University Press, All rights reserved. 1 CHAPTER 2 THE EARTH IN SPACE AND TIME

Chapter 2 © Oxford University Press, All rights reserved. 1 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

Chapter 2 © Oxford University Press, All rights reserved. 1 THE EARTH IN TIME Meteorites and the Earth The age of the Earth The Earth’s atmosphere Geological time scales Life on Earth

Chapter 2 © Oxford University Press, All rights reserved. 1 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

Chapter 2 © Oxford University Press, All rights reserved. 1 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

Chapter 2 © Oxford University Press, All rights reserved. 1 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)

Chapter 2 © Oxford University Press, All rights reserved. 1 VOLCANOES – EFFECTS Lava flows, pyroclastics – boulders, ash Fine dust to 20 km into atmosphere Gases and steam, including SO 2, CO 2 Ash cones or extensive lava flows

Chapter 2 © Oxford University Press, All rights reserved. 1 CONTINENTAL MARGINS Plate boundaries and continental margins Continental shelf Exogenic forces and sedimentation on shelf Sediment ‘starvation’ (large dams) leads to ocean encroachment

Chapter 2 © Oxford University Press, All rights reserved. 1 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