Earth Structure and Seismic Activity Lecture Notes

Vocabulary-style flashcards covering Earth's internal structure, plate tectonics, earthquake measurement, and case studies of seismic impact.

Crust

The outer layer of the Earth, measuring between $5-70\,\text{km}$ thick.

Mantle

The semi-molten layer located beneath the crust that is approximately $\sim 2900\,\text{km}$ thick.

Outer Core

The layer of the Earth consisting of liquid iron and nickel.

Inner Core

The hottest layer of the Earth, consisting of solid iron and nickel.

Tectonic Plates

Large pieces of the Earth’s crust that are moved by convection currents.

Convection Currents

The circular movement of heat in the mantle where hot material rises, cools, then sinks, dragging tectonic plates.

Continental Crust

A thicker, less dense type of crust made of older rock, such as that found in Africa.

Oceanic Crust

A thinner, denser type of crust made of younger rock, such as the Pacific Ocean floor.

Pangea

The supercontinent where all continents were once joined approximately $\sim 220$ million years ago.

Plate Boundary

The specific location where two tectonic plates meet.

Constructive Boundary

A boundary where plates move apart, allowing magma to rise, cool, and form new crust.

Destructive Boundary

A boundary where plates move together and the denser oceanic plate subducts beneath the continental plate.

Conservative Boundary

A boundary where plates slide past each other, building friction that results in a sudden release of energy as earthquakes.

Collision Boundary

A boundary where two continental plates of the same density collide and crumple upwards to form fold mountains.

Subduction

The process where a denser tectonic plate sinks under another plate at a destructive boundary.

Hotspot

An area of volcanic activity that occurs away from plate boundaries, such as Hawaii.

Pacific Ring of Fire

A major global pattern depicting a high concentration of earthquakes and volcanoes around the Pacific Ocean.

Seismometer

An instrument used to measure ground vibrations caused by earthquakes.

Seismograph

An instrument that records the seismic waves detected by a seismometer.

Magnitude

A measurement of the strength or energy released by an earthquake.

Richter Scale

A logarithmic scale used to measure the energy released by an earthquake, where each increase represents a $10\times$ increase in strength.

Mercalli Scale

A scale ranging from $I-XII$ used to measure the observed damage caused by an earthquake.

Focus

The specific point underground where an earthquake originates.

Epicentre

The point on the Earth's surface located directly above the earthquake focus.

Primary Effects

The immediate impacts of a disaster, such as deaths, injuries, and infrastructure damage.

Secondary Effects

Impacts that occur after the initial event, including homelessness, disease, lack of water, or tsunamis.

Responses

The specific actions and emergency measures taken after a disaster event occurs.

GDP

Gross Domestic Product; a measure of a country’s wealth used to differentiate between developed and developing nations.

Infrastructure

The basic physical systems of a country, including roads, power grids, and water systems.

Aftershocks

Smaller earthquakes that occur in the period following the main earthquake event.

Tsunami

A large sea wave caused by an earthquake or other underwater disturbance.

Lahar

A fast-moving mudflow associated with volcanic activity.

Pyroclastic Flow

An avalanche of hot gas and ash that moves rapidly down the side of a volcano.

Ash Cloud

Fine volcanic material released into the atmosphere during an eruption.

Geothermal Energy

A renewable energy source harnessed from the internal heat of the Earth.