1. 3.4.1.4 Tectonic processes Volcanic hazards

5. Syllabus details: Relate the distribution and nature of volcanic activity to plate margins and hot spots. Identify the types of eruption and volcanic forms as basic, acid, fissure and composite. Identify primary hazards (such as ash, lava, directed blast, nuée ardente and pyroclastic flows) and secondary hazards (such as landslides, lahars (mudflows) and atmospheric impacts).

7. Relate the distribution and nature of volcanic activity to plate margins and hot spots

14. Hot spots Hotspots are small areas of the crust with an unusually high heat flow and are found away from plate boundaries . Slowly rising mantle rocks create volcanic activity on the surface. The movement of the lithospheric plates over the hot spot produces a chain of what are mainly now extinct volcanoes . Examples of hot spots are Hawaiian Islands , Maldives, Azores. Eruptions are normally of low viscosity basaltic magmas, effusive eruptions

20. Why volcanoes explode

22. Summary table:

29. The largest fragment is about 5 mm in diameter. Tephra between 2 and 64 mm in diamter is called lapilli; tephra <2 mm in diamter is called ash.

34. Mud slide fears over Mexico volcano

36. tsunami

37. Nevado del Ruiz Volcano, Colombia, 1985 USGS website