Chapter 1Living with tectonic hazards

Risk or opportunity?

Gateway 1: Why are some areas more prone to tectonic hazards• Natural hazard: naturally occurring event that

threatens human lives and causes damages to property.

Internal Structure of the Earth

Tectonic Plate

Tectonic PlateOceanic Crust Continental Crust

Beneath deep oceans Beneath earth’s continental land masses and under shallow sea

Between 5-8km Between 30-70km

Consist mainly basaltRocks of less than 200 million years old

Consist of lighter rocksRocks ranges from young to nearly 4 billion years

Why do tectonic plates move?

•Convection currents

•Slab-pull force

Why do tectonic plates move?

• Convection currents are movements of heat within the mantle

• Material in the mantle is heated by the core, causing the mantle material to expand, rise and spread out beneath the plates

• This causes plates to be dragged along and to move away from each other

• Then the hot mantle material cools slightly and sinks, pulling the plate along

Different types of plate movements•Divergent plate boundaries

•Convergent plate boundaries

•Transform plate boundaries

Pairwork

•Each pair choose 1 plate movement and draw the formation of the landform.

•The pair is to explain their diagram to the class.

Select one

•Oceanic-oceanic plate divergence•Continental-continental plate divergence

•Oceanic-oceanic plate convergence•Continental-continental plate convergence

•Oceanic-continental plate convergence

•Transform plate

Oceanic-oceanic plate divergence

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Oceanic-oceanic

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•Magma rises from the mantle to fill the gap between the plates as they diverge.

•New sea floor is formed when the magma cools and solidifies. This process is called sea-floor spreading.

•New sea floor is formed when the magma cools and solidifies. This process is called sea-floor spreading.

•At various points along the ridge, magma builds up above the ocean to form volcanic islands.

Continental- Continental divergence

East AfricanRift Valley

African Plate(Nubian)

African Plate(Somalian)

Block Mountain

Block Mountain

Rift valleys and Block mountains•A fault

▫Fracture in the rocks along which the rocks are displaced

▫Due to tensional forces•Rift Valley

▫Is a valley with steep sides that is formed when the sections of the crust extend along fault lines

•Block Mountain▫A block of land with steep sides

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Oceanic- Oceanic Convergence

Denser Plate Subducts

Oceanic Trench

Crust of subducted plate melts and forms magma

Magma rises through crust and forms volcanoes

Oceanic- Oceanic Convergence

Mariana Islands

Continental crust

Continental crust

Himalayas

Tibetan Plateau

Uppermost mantle

Asthenosphere

EURASIAN PLATE

INDIAN PLATE

Continental- Continental Convergence

Layers of rock compressed together, causing massive folding

Resist subduction

Converging:Continental- Continental

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Fold Mountain Range

Oceanic- Continental convergence

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Converging:Oceanic- Continental

Sunda TrenchBarisan Mountains

Transform plates

Transform plates

•Plates slide past each other along transform plate boundaries.

•The plate movement cause the slow build up of stress on the rocks found on either side of the fault.

•When the rocks can no longer withstand the increasing stress, they can suddenly slip many metres, causing an earthquake.