12. VULNERABILITY NATURAL HAZARD RISK OF DISASTER Sudden events and chronic issues Past recurrence intervals Future probability Speed of onset Magnitude Duration Areal extent Exposure, sensitivity and resilience of: Population Economy Land use and development Infrastructure and critical facilities Cultural assets Natural resources Source: Geography for EDEXCEL by Digby et al (Oxford University Press) EARTHQUAKES VENN DIAGRAM The connection between natural hazard events and locational site vulnerability

13. What does this map show?

14. Distribution of earthquakes & major plate boundaries

16. Major plate boundaries superimposed on political map

17. Live volcanoes superimposed on political map

18. Detailed tectonics map

20. The structure of the Earth The Earth is made up of an inner core, outer core, mantle and crust. The crust and upper mantle form a cold, strong layer known as a lithosphere.

22. Many forces cause the surface of the Earth to change over time. However, the largest force is the movement of Earth's outer layer through the process of plate tectonics. This process causes mountains to push higher and oceans to grow wider. The rigid outer layer of the Earth, called the lithosphere, is made of plates which fit together like a jigsaw puzzle. These solid but lightweight plates seem to "float" on top of a more dense, fluid layer. Motions deep within the Earth carry heat from the hot interior to the cooler surface. These motions of material under the Earth's surface cause the plates to move very slowly across the surface of the Earth, at a rate of about 2 inches per year. There are several different hypotheses to explain exactly how these motions allow plates to move.

23. This image is a cross section through the Earth showing the convection cells of the mantle. Ridge push happens at spreading centres where plates are moving apart. Slab pull happens at subduction zones where one plate is pulled down into the mantle. The Earth’s core is intensely hot at about 5000 o C. This heat causes molten rock deep within the mantle to rise. As it nears the surface it cools, becomes more dense and sinks back down. It is again heated so that once again it is forced to rise.This constant circular motion is called a convection cell. Hot magma rises to the surface to create spreading ridges. As new crust is formed existing crust is actively pushed out of the way. This is called ridge push. Old parts of a plate are likely to sink down into the mantle at subduction zones because they are colder, thicker and denser than the warm mantle material underneath them. This is called slab pull. Why do the plates move?

26. Iceland Ocean floor spreading

27. Divergent (constructive) plate margin - ocean floor spreading along the plate boundary. A volcanic ridge has developed as lava fills the gap as the plates move apart North American Plate Eurasian Plate The Azores - a group of islands formed as the ocean floor volcanic activity eventually broke surface Iceland, several thousand kms north of here was formed in a similar way. However, unlike the Azores, it is still growing because the plate boundary runs through the middle. So where in Iceland would you go to see its oldest rocks?

29. Mariana Trench Philippines Plate Pacific Plate The western edge of the westerly spreading Pacific Plate is over 170 million years old which means it has had a huge amount of time to compact and become exceptionally dense. This has led to its great height-difference (which translates to water depth) relative to the higher-riding Mariana Plate, a small section of the larger Philippines Plate, at the point where the Pacific Plate crust is subducted (forced down beneath the other). This is the deepest part of any ocean and at over 11,000m is deeper than Mt Everest is high The Philippines Southern Japan Indonesia Malaysia Taiwan Papua New Guinea Subduction

30. Plate movements have led to continental drift. 225 million years ago all the land masses were fused to form a super-continent - Pangea. 200 million years ago Pangea began to move apart to form two great land masses - Laurasia and Gondwanaland. About 135 million years ago it was possible to make out land masses that looked more like those we see today. For example it is possible to see how South America and Africa were drifting apart to form separate continents.

31. The End