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)
Slide 3
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)
Slide 4
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)
Slide 5
Volcano An opening in the Earths crust where lava, ash and
gases erupt Magma = Molten material within the earths surface Lava
= Magma exposed to the atmosphere
Slide 6
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
Slide 7
Intrusive
Slide 8
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)
Slide 9
Laccolith When the squeezed material from a batholith collects
and causes uplift to the land above
Slide 10
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)
Slide 11
Sill Formed like a dyke but the magma spreads along the lie of
pre-existing geology such as sedimentary layers Whin Sill in
Northumberland
Slide 12
Volcanic features in the UK
Slide 13
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..
Slide 14
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
Slide 15
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
Slide 16
Slide 17
Extrusive Landform. Volcano Watch the Video Make notes on the
types of volcano, use P11- 12 (Smith and Knill) on the hand-out to
help
Slide 18
Classification Active: Is erupting or has erupted in past few
decades Dormant: Hasnt 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
Slide 19
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