1. Shield Volcanoes Basaltic Lava – low silica content, low viscosity, low gas content Hot spots – magma moves up from lower mantle and plates move over it Ex. Hawaii (note: see video on favorites)

2. Shield Volcanoes Mid Ocean Ridges - volcanoes grow out of mid ocean ridges (constructive margin) – Ex: Iceland – only MOR with an actual volcano Divergent boundary – forming islands from accumulation of basaltic lava

3. Contd. Fissures – a crack! The beginning of volcanic activity as magma moves up through the crack towards the surface

4. Anatomy of a volcano

5. Shield Volcanoes Broad shape, gentle slopes - Why??? Quiet eruptions – Why?? – Lava flows - Basaltic lava – Why?? From vents and craters – why?? 70% of all gases produces from volcanoes is water vapor

6. Cinder Volcanoes Cinder Cones – smallest volcanoes usually products of a single volcanic eruption lasting only a few weeks (rarely more than 1 year) Forms on continents tall with steep slopes Extremely violent eruptions

7. Eruptions Very high silica content Very little to no lava flow – why?

8. Eruption characteristics Once cinder cone volcanoes erupt the pipe that connects the vent to the chamber solidifies and volcano never erupts again Fragments that come from eruption range from ash to bombs but consists mostly of lapilli (cinders) 2-64 mm in size

9. Pyroclastic materials Lapilli – cinders ranging from 2-64 mm in size Bombs- semimolten material upon ejection and become streamlined after ejection Blocks – particles that are larger than 64mm in size.