Geography Video Notes: Earth Structure, Volcanoes, Earthquakes, and Global Atmospheric Systems

Vocabulary flashcards covering Earth’s structure, plate tectonics, volcanoes, earthquakes, and atmospheric/climate concepts from the lecture notes.

Crust

The outermost solid layer of the Earth; oceanic crust is thin (about 5–10 km) and basaltic; lies beneath the oceans.

Mantle

The thick middle layer of the Earth (about 2900 km thick) where rocks are hot and can melt; convection currents occur.

Core

Earth's hottest region (around 5000°C); composed mainly of iron and nickel; inner core is solid, outer core is liquid.

Lithosphere

The rigid outer shell of the Earth, including the crust and upper mantle; broken into tectonic plates.

Asthenosphere

Semi-molten layer beneath the lithosphere; convection currents in this layer drive plate movement.

Convection Currents

Heat-driven circulation in the mantle that causes movement of tectonic plates.

Plate Margins

Boundaries between tectonic plates; include destructive, constructive, and conservative margins.

Destructive Plate Margin

One plate subducts beneath another; magma forms volcanoes and earthquakes occur.

Constructive Plate Margin

Two plates move apart; magma rises to form new crust, often along submarine ridges.

Conservative Plate Margin

Plates slide past one another; earthquakes occur without major volcanism (e.g., San Andreas Fault).

Focus

The exact point inside the Earth where an earthquake originates.

Epicentre

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

Shallow Focus

Earthquakes with shallow depth; localized damage; common on destructive margins.

Deep Focus

Earthquakes with greater depth; seismic waves can affect wider areas.

Mercalli Scale

Qualitative scale assessing earthquake intensity based on observed effects.

Richter Scale

Logarithmic scale measuring the magnitude of an earthquake's energy.

Seismometer

Instrument used to detect and record seismic waves from earthquakes.

Volcano

A vent or fissure through which magma, lava, ash, and gases erupt onto the surface.

Composite Volcano

Common on land; built from alternating layers of ash and lava; eruptions are explosive.

Hotspots

Volcanoes formed away from plate boundaries due to rising magma plumes; e.g., Hawaii.

Ash Cloud

A cloud of volcanic ash ejected into the atmosphere during eruptions.

Volcanic Gas

Gases released during eruptions (e.g., sulfur dioxide, water vapor, carbon dioxide).

Lahar

Volcanic mudflow that travels down valley sides when volcanic material mixes with water.

Pyroclastic Flow

Fast-moving current of superheated gas and volcanic ash (around 1000°C; up to ~450 mph).

Volcanic Bomb

Large lumps of molten rock ejected during an eruption and solidified in the air.

Hotspot Eruptions

Eruptions fed by magma plumes beneath the crust; often gentle and predictable.

Hadley Cell

Global atmospheric circulation cell from the equator to roughly 30°–40° latitude in each hemisphere.

Ferrel Cell

Mid-latitude atmospheric circulation cell between about 30° and 60° latitude.

Polar Cell

Smallest atmospheric cell near the poles; air tends to descend leading to dry conditions.

High Pressure

Air mass with sinking air; usually clear skies and calm weather.

Low Pressure

Air mass with rising air; associated with clouds, rain, and unsettled weather.

Temperate Climate

Moderate climate with distinct seasons and rainfall patterns typical of mid-latitudes.

Tropical Climate

Hot, humid climate near the equator with heavy rainfall.

Polar Climate

Very cold climate near the poles with dry, icy conditions.

Desert Climate

Dry climate with low precipitation and high temperatures.

Trade Winds

Winds blowing from subtropical high-pressure belts toward the equator.

Jet Streams

Fast-flowing air currents in the upper atmosphere that influence weather patterns.

Frontal Rainfall

Rain produced when a warm air mass meets a cooler air mass and rises over it.

Convectional Rainfall

Rain produced when land heats up, causing warm air to rise and condense.

Katabatic Winds

Winds that flow down slopes due to gravity, often in high-elevation areas.

El Niño

Climate pattern where warm water shifts across the eastern Pacific, altering weather globally (often droughts in some regions and heavy rainfall in others).

Tropical Storm

Tropical cyclone with sustained winds of 39–73 mph; becomes a hurricane at 74 mph.

Hurricane / Typhoon / Cyclone

Tropical cyclone naming differences by region; forms over warm tropical oceans.

Eye of the Storm

Calm center of a tropical cyclone where winds are light.

Anticyclone

High-pressure system associated with settled, hot, and dry conditions (often linked to heatwaves).

UK Heatwave 2003 (Case Study)

Extreme heat event caused by persistent high pressure; led to heat-related deaths and disruption; measures included public guidance and water-use restrictions.