Hazard Earth: Tectonics

Question 1

What are convection currents?

Answer 1

Tectonic plates are continually moving on the asthenosphere because of hot rising currents called convection currents.

Rock is heated by the lower mantle and rises.

After is slowly begins to cool.

When it reaches the asthenosphere it turns sideways.

Eventually it cools and sinks.

Question 2

What is the asthenosphere?

Answer 2

Asthenosphere is the denser part of the upper mantle

Temperature is high (Above 1300 degrees)

Question 3

What is the lithosphere?

Answer 3

This includes the crust and the top layer of the upper mantle.

It is broken up into tectonic plates.

Question 4

What are convergent plate boundaries?

Answer 4

Plates move towards each other

Oceanic plate meets continental plate

Oceanic is more dense so it sinks under the continental plate (subduction)

Leading to a composite volcano

Question 5

What are divergent plate boundaries?

Answer 5

Divergent plate boundaries is when the plate moves apart

The magma rises to fill the gap / rift valley

Forming a shield volcano

Question 6

What are conservative plate boundaries?

Answer 6

Plates slide past one another

Pressure builds along the boundary causing an earthquake

Question 7

What type of lava is erupted from composite volcanoes?

Answer 7

Andesitic lava which is more viscous (thick and sticky)

Question 8

What type of lava flows from shield volcanoes?

Answer 8

Basaltic lava is erupted from shield volcanoes

Less viscous.

Question 9

How are hotspots formed?

Answer 9

They are formed by a plume of superheated rock rising very slowly through the mantle.

Question 10

How do you measure the size of an earthquake?

Answer 10

The size of an earthquake is recorded using a seismometer.

The magnitude is then given according to the Richter scale

Question 11

What is the focus of an Earthquake?

Answer 11

The point of rupture - where the earthquake happens underground.

Question 12

What happens at a conservative plate boundary?

Answer 12

In a conservate plate boundary, convection currents cause the plates to slide past each other which can cause earthquakes due to built up pressure.

Question 13

What are the differences of basaltic and andesitic lava?

Answer 13

Andesitic is more viscous so that is flows more slowly.

Basaltic is less viscous which is more runny and flows faster.

Question 14

Name 4 Primary impacts of the Pinatubo eruption.

Answer 14

Pinatubo Eruption, Philippines, 1991:

847 people were killed in the main eruption, many by pyroclastic flows and ash falls.

The ash cloud caused the region to become cold and dark, hampering rescue operations.

5000 homes destroyed. As well as Typhoon Yunya struck at the same time.

Many people were displaced to shanty towns.

Question 15

Name 3 Secondary impacts of the Pinatubo eruption.

Answer 15

As winds dispersed the gas cloud, global temperatures dropped 0.5 degrees.

Hundreds of people died from disease in evacuation camps.

Crops were destroyed as ash covered 800km of rice fields.

800000 farm animals were killed costing around 1.5billion pesos.

Question 16

How are tsunamis usually triggered.

Answer 16

Tsunamis are usually triggered by earthquakes and are usually secondary hazards.

Question 17

Name 3 primary impacts of the Tohoku Earthquake, Japan, 2011.

Answer 17

667 - 1479 deaths as a direct result of the earthquake. Mainly by collapsing buildings.

Many buildings severely damaged.

Electric power and sewerage systems were disrupted.

Question 18

What are Name 3 secondary impacts of the Tohoku Earthquake, Japan, 2011.

Answer 18

The vast majority of deaths, 17000+, caused by a tsunami.

5000 or more were reported injured or missing.

127000 buildings collapsed.

Question 19

Name 3 ways to reduce buildings collapsing in the case of an earthquake.

Answer 19

Deep foundations and wide base for stability.

Automatic window shutters to prevent glass falling.

Steel frames which can sway during earth movement.