tectonic hazards

What is the Earth’s crust divided into?

Tectonic plates.

What are the two types of crust?

• Oceanic

• Continental

What are the characteristics of oceanic crust?

• Thin

• Heavy + dense

• Young

What are the characteristics of continental crust?

• Thick

• Light

• Old

Why do plates move?

Because of the convection currents in the mantle of the Earth.

Where do most earthquakes and volcanic eruptions occur?

By plate boundaries.

Why do most earthquakes and volcanic eruptions occur by plate boundaries?

Due to the tectonic activity occurring at plate boundaries - the movement of plates causes earthquakes and the rise of magma at destructive + constructive plate boundaries forms volcanoes

What are the 3 main types of plate margin?

• Destructive

• Constructive

• Conservative

How do the plates of a destructive plate boundary move relative to each other?

They move towards each other.

What are the two types of destructive plate boundary?

• Subduction (oceanic + continental)

• Collision (continental + continental)

What hazards occur at a destructive plate boundary?

• Earthquakes

• Volcanic eruptions

What landforms are formed at a destructive plate boundary?

• Volcanoes (S)

• Deep sea trenches (S)

• Fold mountains (C)

How is a deep sea trench and volcano formed at a (subduction) destructive plate boundary?

1. The oceanic plate subducts beneath the continental plate into the mantle, forming a deep sea trench.

2. This causes the subducted part of the oceanic plate to melt and create more magma

3. The magma rises into the cracks + breaks through to the surface of the continental plate.

4. Eventually when the pressure is high enough, it erupts, forming a volcano.

EX: Atacama Trench (Nazca + South American)

How are fold mountains formed at a (collision) destructive plate boundary?

The collision between the two continental plates causes the crust to fold upwards, forming fold mountains.

EX: Himalayas

How do the plates of a constructive plate boundary move relative to each other?

They move away from each other.

What hazards occur at a constructive plate boundary?

• Earthquakes

• Volcanic eruptions

What landforms are formed at a constructive plate boundary?

• Mid ocean ridges

• Volcanoes

How is a mid ocean ridge formed at a constructive plate boundary?

As the two oceanic plates move away from each other, magma rises to fill the gap. This solidifies and forms new oceanic crust, forming a mid ocean ridge.

EX: Mid-atlantic ridge (Eurasian + North American)

How is a volcano formed at a constructive plate boundary?

As the two plates move away from each other, magma rises to the surface of the crust which erupts to form a volcano.

How do the plates of a conservative plate boundary move relative to each other?

They move past each other, either in the same direction and at different speeds or in opposite directions.

EX: San Andreas Fault (Pacific + North American)

What hazards occur at a conservative plate boundary?

Only earthquakes.

What landforms occur at a conservative plate boundary?

None.

What is the primary effect of a hazard?

The immediate impact caused directly by a hazard.

What is the secondary effect of a hazard?

The indirect impacts of a hazard that occur as a result of the primary effects.

What are the primary effects of an earthquake?

• People are killed or injured by collapsing buildings + falling debris

• Homes, schools, hospitals, and other buildings are destroyed

• Roads, bridges, railways, and ports are damaged

• Water pipes, gas mains, and electricity cables are broken

What are the secondary effects of an earthquake?

• Rescue and emergency services may be delayed due to blocked roads + damaged infrastructure

• Fires break out from leaking gas pipes or fallen power cables

• Burst water pipes lead to shortages of clean water, increasing the risk of disease

• May trigger a tsunami or landslide

• People are left homeless

• Economic activity is disrupted, with businesses closed (causing unemployment + a loss of income) and expensive repair + reconstruction costs

What are the primary effects of a volcanic eruption?

• Lava flows, ash, and pyroclastic flows destroy buildings, roads, + farmland

• People and animals are killed or injured by hot gases, ash, or debris

• Air travel is disrupted or cancelled due to ash clouds in the atmosphere

• Ash and gases contaminate water supplies

What are the secondary effects of a volcanic eruption?

• Access to remote areas may be cut off, slowing down aid and rescue efforts

• Glaciers and snow on volcanoes melt, causing floods

• People are left homeless

• Heavy rain can mix with ash to create lahars (volcanic mudflows) that bury settlements

• Tourism may increase as visitors are drawn to see the volcano and its impacts

• Volcanic ash can make land more fertile when broken down

• High costs of reconstruction, unemployment + loss of income (due to destruction of businesses) weaken the economy

What are immediate responses to a tectonic hazard?

• Issuing warnings

• Rescue teams searching for survivors

• Providing treatment to injured people

• Providing clean drinking water

• Recovering bodies.

• Extinguishing fires

What are long-term responses to a tectonic hazard?

• Rebuilding and repairing properties

• Rebuilding and repairing transport infrastructure

• Improving building regulations

• Restoring utilities such as water, electricity and gas

• Resettling local people

• Developing opportunities for the economy to recover

• Install monitoring equipment