MP Cohort Revision 1

Name the layers of the Earth from innermost to outermost.

Inner core, outer core, mantle, crust, lithosphere

What is the lithosphere?

The rigid crust and upper mantle, broken into tectonic plates

What is the asthenosphere?

The semi-molten mantle below the lithosphere where convection occurs

What is the density of oceanic crust?

~3.0 g/cm³

What is the density of continental crust?

~2.7 g/cm³

Name the main tectonic plates.

Pacific, North American, South American, African, Eurasian, Antarctic, Indo

What is a plate boundary?

The edge of tectonic plates where most earthquakes and volcanoes occur

How do tectonic plates move?

Via convection currents in the mantle, causing divergence, convergence, or lateral movement

Name the three main types of plate boundary.

Divergent/constructive, convergent/destructive/collision, conservative/transform

Give an example of a constructive/divergent boundary.

Eurasian Plate and North American Plate at the Mid-Atlantic Ridge

Give an example of a destructive/convergent boundary.

Nazca Plate and South American Plate at the Andes subduction zone

Give an example of a collision boundary.

Indian Plate and Eurasian Plate at the Himalayas

Give an example of a conservative/transform boundary.

North American Plate and Pacific Plate at the San Andreas Fault

Where do most earthquakes occur?

At plate boundaries, along fault lines

What is an earthquake?

A sudden shaking of the Earth caused by stress release at a fault

What is the focus?

The point underground where the earthquake starts

What is the epicentre?

The point on the surface above the focus

What are seismic waves?

Energy waves that travel through the Earth after an earthquake

ame two types of seismic waves.

P-waves (fast, compressional), S-waves (slower, shear)

What are Love waves?

Seismic surface waves causing horizontal ground movement; very destructive

What are Rayleigh waves?

Seismic surface waves causing rolling, elliptical motion, damaging to buildings

Explain the sequence of an earthquake.

Plates stick, pressure builds, sudden slip, seismic waves radiate

What scale measures earthquake magnitude?

Moment Magnitude Scale (or Richter Scale)

What scale measures earthquake intensity?

Mercalli Scale

Name a secondary effect of an earthquake.

Tsunamis, landslides, building collapse

Why do people live in earthquake zones?

Fertile soils, mineral resources, jobs, culture

What is a tsunami?

A giant sea wave triggered by underwater earthquakes

What is magma?

Molten rock beneath the Earth's surface

What is lava?

Molten rock on the surface

Name the main features of a volcano.

Crater, vent, magma chamber, secondary cone

What is a shield volcano?

A wide, gently sloping volcano with basaltic lava flows

Give an example of a shield volcano.

Mauna Loa, Hawaii

What is a composite/strato volcano?

Tall, steep-sided volcano made of layers of ash and lava

Give an example of a composite volcano.

Mount Fuji, Japan

What is a cinder cone volcano?

Small, steep volcano built from cinders and tephra

Give an example of a cinder cone.

Paricutin, Mexico

How are volcanoes classified by activity?

Active, dormant, extinct

Name 3 volcanic hazards.

Lava flows, pyroclastic flows, ash falls

What is a lahar?

A mudflow of volcanic ash and water

What is tephra?

Fragments of rock and ash ejected during eruptions

How does the speed of a volcanic hazard affect its impact?

Faster hazards cause more destruction and less time to evacuate

Why is the size/frequency of eruptions important?

Larger/frequent eruptions increase risk and damage

Give an example of a toxic gas from volcanoes.

Sulphur dioxide (SO₂)

What is a pyroclastic flow?

A fast-moving, hot gas and ash cloud

How do lahars differ from pyroclastic flows?

Lahars are mud/ash, slower; pyroclastic flows are hot, fast, gas

Name a positive effect of volcanic eruptions.

Fertile soils or tourism/research opportunities

What is a secondary cone?

A smaller vent/cone forming on the side of the main volcano

When did the Tohoku earthquake occur?

11th March 2011

What was its magnitude?

9.0 (Moment Magnitude Scale)

Which plates caused it?

Pacific Plate subducting under North American Plate

What was the depth of the focus?

30 km

Main primary hazard?

Tsunami

How high were the tsunami waves?

Up to 40 metres

Name a secondary effect.

Fukushima nuclear meltdown

Number of deaths?

Around 20,000

Economic cost?

$235 billion

One long-term response?

Higher sea walls, tsunami warning systems

Where is Montserrat?

Caribbean island

When did the eruption start?

18th July 1995

Volcano type?

Composite/Stratovolcano

Which plates caused it?

Atlantic Plate subducting beneath Caribbean Plate

Main hazard?

Pyroclastic flows

How many deaths?

19 people

Capital affected?

Plymouth buried

% of island uninhabitable?

Two

Migration of population?

Many to the UK

Monitoring installed?

Montserrat Volcano Observatory (MVO)

What is a rift valley?

Lowland formed at divergent boundaries

What is a mid-ocean ridge?

Underwater mountain range at constructive margins

What is an ocean trench?

Deep depression where a plate is subducted

What are fold mountains?

Mountains formed at continental collision zones

What is an accretionary wedge?

Sediments scraped off subducting plate at destructive boundary

What is the Benioff zone?

Zone of earthquake foci down a subducting plate

Difference between continental & oceanic crust?

Oceanic: dense, basalt; Continental: less dense, granite

What is orogeny?

Mountain-building process

Slab pull?

Force from dense sinking plate pulling rest of plate

Ridge push?

Force from elevated mid-ocean ridge pushing plates apart

Conservative boundary?

Plates slide past each other (e.g., San Andreas)

Collision boundary?

Plates crash, forming mountains (e.g., Himalayas)

Destructive boundary?

Oceanic subducts under continental (e.g., Andes)

Constructive boundary?

Plates move apart, magma rises (e.g., Mid-Atlantic Ridge)

What is a primary response?

Immediate actions: rescue, medical aid, food, shelter

What is a secondary response?

Longer-term: rebuilding, planning, infrastructure repair

Example of technology for earthquakes?

Seismometers, GPS

Example of technology for volcanoes?

Gas sensors, satellite imagery

Why do volcanoes erupt at destructive boundaries?

Subduction melts mantle, magma rises

Why do earthquakes occur at conservative boundaries?

Plates stuck, pressure builds, sudden slip

Pyroclastic flow speed?

Up to 600 km/h

Positive human reason for living near a volcano?

Fertile soil, geothermal energy, tourism

Why does magnitude matter in disaster planning?

Determines scale of damage, response required