Unit 4: Geographical Unit 4: Geographical ResearchResearch

Tectonic Activity and HazardsTectonic Activity and Hazards

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

Tectonic landscapes Tectonic landscapes

Lesson 7: What are the landscape Lesson 7: What are the landscape impact of extrusive igneous impact of extrusive igneous

activity? activity? Learning objectivesLearning objectivesTo outline the formation of extrusive To outline the formation of extrusive

igneous landforms such as lava igneous landforms such as lava plateaus and volcanoesplateaus and volcanoes

To investigate the different types of To investigate the different types of volcanoes and eruptionsvolcanoes and eruptions

Extrusive igneous activityExtrusive igneous activity Once extruded onto the surface of the Once extruded onto the surface of the

earth, magma is referred to as earth, magma is referred to as lavalava which which cools to form igneous rockscools to form igneous rocks

The most significant landforms are The most significant landforms are lava lava plateaus and volcanoesplateaus and volcanoes

Their distribution is determined by the Their distribution is determined by the pattern of tectonic platespattern of tectonic plates

Their impact on the landscape with vary Their impact on the landscape with vary according to the according to the magnitude and scale magnitude and scale of the of the events causing them and the events causing them and the types of types of material material being extruded. being extruded.

Lava PlateauLava Plateau

The Deccan PlateauThe Deccan Plateau

VolcanoesVolcanoes

Types of volcanoesTypes of volcanoes

Types of volcanoTypes of volcano

The type of volcano will be affected The type of volcano will be affected by:by:The type of lava eruptedThe type of lava eruptedThe nature of the eruptionThe nature of the eruptionThe type of plate marginThe type of plate margin

Magma type & volcano morphologyMagma type & volcano morphology

BasalticBasaltic – huge, low relief – huge, low relief shield volcanoesshield volcanoes plus small plus small scoria cones and fissure ventsscoria cones and fissure vents..

AndesiticAndesitic – steep sided – steep sided strato-volcanoesstrato-volcanoes; ; layers of lava, ash and tephra.layers of lava, ash and tephra.

RhyoliticRhyolitic – central craters with – central craters with lava plugs / lava plugs / domesdomes, due to high viscosity of the lava., due to high viscosity of the lava.

Types of volcanoTypes of volcanoDivergent marginsDivergent margins Fissure eruptions and Fissure eruptions and

shield volcanoesshield volcanoes Low, gently sloping Low, gently sloping

sides, wide basesides, wide base Basaltic lava, low Basaltic lava, low

viscosity, high temp so viscosity, high temp so covers long distances covers long distances before it cools and before it cools and solidifiessolidifies

Frequent, low Frequent, low magnitude eruptionsmagnitude eruptions

Also found at Also found at hotspotshotspots

Convergent marginsConvergent margins Cone shapedCone shaped Less frequent, more Less frequent, more

explosive eruptionsexplosive eruptions More silica and cooler, More silica and cooler,

so more viscousso more viscous Flows slowly, cools Flows slowly, cools

quickly creating cone quickly creating cone shape with narrow base shape with narrow base and greater heightand greater height

Often composite with Often composite with alternating layers of ash alternating layers of ash and lavaand lava

Watch video

Hawaii – shield volcanoesHawaii – 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 – Soufriere Hills, Montserrat – Composite volcanoComposite volcano

Volcano type Diagram Key features Explanation Example

Fissure

Shield

Dome

Cinder

Composite

Caldera

Wherever possible, try to use examples we have already used e.g. Kiluaea, Montserrat, Yellowstone

Types of eruptionTypes of eruption

Hawaiin – calm, non explosiveHawaiin – calm, non explosiveVulcanian – explosive, short livedVulcanian – explosive, short lived

What type of eruption is associated What type of eruption is associated with your case studies? Why? What with your case studies? Why? What impact has this had? Add this to the impact has this had? Add this to the explanation column on your tableexplanation column on your table

Suggested resourcesSuggested resourcesRead pages 253-255 OUP text bookRead pages 253-255 OUP text bookPages 162-165 Byrne et alPages 162-165 Byrne et alPage 67 Frampton et alPage 67 Frampton et alPage 14-15 NaglePage 14-15 NaglePage 22-26 WaughPage 22-26 WaughNational geographic “Forces of nature” National geographic “Forces of nature”

– see types of volcano link on Moodle– see types of volcano link on MoodleExplore google earth locationsExplore google earth locations

Next lesson ….Next lesson ….

Intrusive igneous landformsIntrusive igneous landforms