1. An Introduction to Geology: 5 A Bit More Time

2. A sedimentary recap Bedding

3. Sedimentary structures Cross-bedding

4. Sedimentary structures Cross-bedding

5. Sedimentary structures Ripple marks

6. Sedimentary structures Shell beds

7. Sedimentary structures Trace fossils

8. Sedimentary Britain At the surface, most of the UK is sedimentary

9. Life layer writing Ediacaran PALAEOZOIC: Cambrian Ordovician Silurian Devonian Carboniferous Permian MESOZOIC: Triassic Jurassic Cretaceous CAINOZOIC Palaeogene Neogene Quaternary

10. Made Your Own Mnemonic? Fabulous* prizes for the best ones! *Fossils

11. The Dating Game Relative Chronology versus Absolute Chronology

12. Problems of relative dating

13. The absolute challenge Q. How can we determine how old rocks are?

14. Sedimentation rates? Phillips (1860) = 38-96 million years old

15. By heat loss? Kelvin (1862-1897) = 20-40 million years old

16. By ocean saltiness? Joly (1897-99) = 80-100 million years old

17. A. By using isotopes! Pierre & Marie Curie 84 natural elements 339 isotopes

18. Isotopes Atoms of a chemical element can have different numbers of neutrons Isotopes of hydrogen

19. A. By radioactivity! Pierre & Marie Curie 84 natural elements 339 isotopes – Stable – Radioactive 70 radioactive isotopes 18 with long half- lives

20. Half-lives Nuclei of radioactive atoms decay Parents and daughters: C-14 decays to N-14 K-40 decays to Ar-40 U-238 to Pb-206 (via a decay chain) Ernest Rutherford

21. Half-lives Nuclei of radioactive atoms decay Ernest Rutherford Constant decay rate: Half-life = time to get 50:50 parent:daughter

22. Igneous importance Decay begins once magma crystallizes

23. Holmes: radioactive rock detective Earth is billions of years old

24. Geological application U-Pb dating of zircons particularly powerful (ZrSiO4) 4.374bn (+/- 6 Ma) year-old zircon crystal, Western Australia

25. Combined chronology ABSOLUTE – Radiometric analysis only possible for igneous (and some metamorphic) minerals – Expensive, difficult, slow RELATIVE – Fossils widespread, common, cheap and fast to analyse

26. Common igneous rocks Granite Intrusive Coarse-grained Felsic

27. Common igneous rocks Basalt Extrusive Fine-grained Mafic

28. Common igneous rocks Dolerite Hypabyssal Medium- grained Mafic

29. Common igneous rocks Gabbro Intrusive Coarse- grained Mafic

30. Common igneous rocks Rhyolite Extrusive Fine-grained Felsic

31. Common igneous rocks Andesite Extrusive Fine-grained Intermediate

32. Completing the Rock Cycle Tectonics & Metamorphism

33. Completing to the Rock Cycle Tectonics & Metamorphism