Volcanicity Quality or state of being volcanic

Good or Bad? Make a list of all the benefits of volcanicity Make a list of all the specific hazards of volcanic activity (e.g lava buries and burns)

Benefits New land (Hawaii) Hot rocks = Geothermal energy (Iceland) Igneous rocks contain valuable minerals Sulphur widely used in pharmaceuticals Strong building material (Aberdeen granite) Extinct volcanic plugs make good defensive sites (Edinburgh Castle) Lava and Ash quickly weather to give fertile soils Tourist revenue (Vesuvius)

Hazards Lava burns and buries crops/towns Submarine eruptions may trigger tsunami Ash can kill crops or disrupt air travel (Iceland). It also causes breathing problems for asmatics Ash and dust mixed with rain lead to Lahars (mudflows) Flooding from debris blocking rivers Pyroclastic flows (Rapid, superheated gas) Heat melts snow causing flooding/lahars Dust may absorb solar energy reducing surface temperatures (Krakatoa)

Volcano An opening in the Earth’s crust where lava, ash and gases erupt Magma = Molten material within the earth’s surface Lava = Magma exposed to the atmosphere

Molten material within the earth is kept at tremendous temperature and pressure As they move into the crust they begin to cool. Extrusive: The magma has been exposed to the atmosphere Intrusive: Cooled within the crust so never making the surface

Intrusive

Batholith Half dome in Yosemite Large amounts of magma cool very slowly (as surrounded by hot rock). Produces a large mass made of course grained rocks)

Laccolith When the squeezed material from a batholith collects and causes uplift to the land above

Dyke Magma from the batholith is squeezed up between existing strata. Dykes usually are vertical and go against the existing lie of the geology (Kildonan Isle of Aran)

Sill Formed like a dyke but the magma spreads along the lie of pre-existing geology such as sedimentary layers Whin Sill in Northumberland

Volcanic features in the UK

Extrusive As the air (or the sea) is much cooler than the hot rock below, magma which becomes lava cools faster so is made of much finer grains. Extrusive landforms are a combination of different things…..

Gas – Steam (often superheated), carbon monoxide, hydrogen sulphide, sulphur dioxide, choline (all very toxic) Solids – Ash, dust, glass cinders (can vary in size) Liquid – Lava bombs (become solid in mid air as they cool). Example = Pumice

Lava Basaltic – Most common at hot spots, low in silica. Formed as magma moves upwards so gas can expand allowing a runny texture Andesitic – Found at destructive plate boundaries. Rich in silica, less runny Rhyolitic – Most viscous, found at destructive margins. Pressure stops gas from expanding resulting in explosions

Extrusive Landform……. Volcano Watch the Video Make notes on the types of volcano, use P (Smith and Knill) on the hand-out to help

Classification Active: Is erupting or has erupted in past few decades Dormant: Hasn’t erupted recently (see above) but is likely to again in the future Extinct: Has not erupted in previous 10,000 years and unlikely to in the future

Homework Find examples of the different types of volcano from around the world Look at reports of their previous eruptions and try to match them up to the table on the next slide