Unit 4: Geographical Research Tectonic Activity and Hazards

What are these? Where are they? How did they get there?

Tectonic landscapes

Lesson 7: What are the landscape impacts of extrusive igneous activity? Learning objectives To outline the formation of extrusive igneous landforms such as lava plateaus and volcanoes To outline the formation of extrusive igneous landforms such as lava plateaus and volcanoes To investigate the different types of volcanoes and eruptions To investigate the different types of volcanoes and eruptions

Extrusive igneous activity Once extruded onto the surface of the earth, magma is referred to as lava which cools to form igneous rocks Once extruded onto the surface of the earth, magma is referred to as lava which cools to form igneous rocks The most significant landforms are lava plateaus and volcanoes The most significant landforms are lava plateaus and volcanoes Their distribution is determined by the pattern of tectonic plates Their distribution is determined by the pattern of tectonic plates Their impact on the landscape with vary according to the magnitude and scale of the events causing them and the types of material being extruded. Their impact on the landscape with vary according to the magnitude and scale of the events causing them and the types of material being extruded.

Lava Plateau

The Deccan Plateau

Volcanoes

Types of volcanoes

Types of volcano The type of volcano will be affected by: The type of volcano will be affected by: The type of lava erupted The type of lava erupted The nature of the eruption The nature of the eruption The type of plate margin The type of plate margin

Magma type & volcano morphology Basaltic – huge, low relief shield volcanoes plus small scoria cones and fissure vents. Basaltic – huge, low relief shield volcanoes plus small scoria cones and fissure vents. Andesitic – steep sided strato-volcanoes; layers of lava, ash and tephra. Andesitic – steep sided strato-volcanoes; layers of lava, ash and tephra. Rhyolitic – central craters with lava plugs / domes, due to high viscosity of the lava. Rhyolitic – central craters with lava plugs / domes, due to high viscosity of the lava.

Types of volcano Divergent margins Fissure eruptions and shield volcanoes Fissure eruptions and shield volcanoes Low, gently sloping sides, wide base Low, gently sloping sides, wide base Basaltic lava, low viscosity, high temp so covers long distances before it cools and solidifies Basaltic lava, low viscosity, high temp so covers long distances before it cools and solidifies Frequent, low magnitude eruptions Frequent, low magnitude eruptions Also found at hotspots Also found at hotspots Convergent margins Cone shaped Cone shaped Less frequent, more explosive eruptions Less frequent, more explosive eruptions More silica and cooler, so more viscous More silica and cooler, so more viscous Flows slowly, cools quickly creating cone shape with narrow base and greater height Flows slowly, cools quickly creating cone shape with narrow base and greater height Often composite with alternating layers of ash and lava Often composite with alternating layers of ash and lava Watch video

Hawaii – shield volcanoes Oceanic hotspot location Volcanoes formed by tectonic plate moving north west over hotspot Gently sloping sides New volcano, 3000m tall and 2000m below sea

Soufriere Hills, Montserrat – Composite volcano

Volcano typeDiagramKey featuresExplanationExample Fissure Shield Dome Cinder Composite Caldera Wherever possible, try to use examples we have already used e.g. Kiluaea, Montserrat, Yellowstone

Types of eruption Hawaiin – calm, non explosive Hawaiin – calm, non explosive Vulcanian – explosive, short lived Vulcanian – explosive, short lived What type of eruption is associated with your case studies? Why? What impact has this had? Add this to the explanation column on your table What type of eruption is associated with your case studies? Why? What impact has this had? Add this to the explanation column on your table

Suggested resources Read pages OUP text book Read pages OUP text book Pages Byrne et al Pages Byrne et al Page 67 Frampton et al Page 67 Frampton et al Page Nagle Page Nagle Page Waugh Page Waugh National geographic “Forces of nature” – see types of volcano link on Moodle National geographic “Forces of nature” – see types of volcano link on Moodle Explore google earth locations Explore google earth locations

Next lesson …. Intrusive igneous landforms Intrusive igneous landforms