Edexcel GCSE A Geography Paper 1 Revision Notes

Types of Natural Hazards

Natural hazards split into two main categories that you need to know inside out. Geological hazards include volcanoes, tsunamis, and earthquakes - basically anything caused by the Earth's structure. Climatic hazards cover weather-related disasters like droughts, blizzards, heatwaves, and tropical storms.

You might wonder why millions of people choose to live near these dangerous areas. The answer is surprisingly practical - volcanic soil is incredibly fertile for farming because of the ash deposits. Some areas rely heavily on tourism (think tropical storm zones), whilst others benefit from geothermal energy for heating and electricity.

Hazard risk assessment is how scientists judge potential damage in different areas. This helps governments plan evacuations and build defences where they're needed most.

Quick Tip: Remember that people don't just ignore hazards - they often get real benefits from living near them!

Hurricane Formation and Structure

Hurricanes are nature's most powerful storms, but they need very specific conditions to form. The ocean must be at least 27°C and 60 metres deep, positioned between 5-30 degrees north or south of the equator. Think of it like a recipe - get one ingredient wrong and the hurricane won't develop.

Here's how it works: warm ocean water evaporates and rises, creating low pressure at the surface. Surrounding air rushes in to fill this gap, but Earth's rotation creates the Coriolis effect, making the whole system spin. Northern hemisphere hurricanes spin anticlockwise, southern hemisphere ones go clockwise.

The storm feeds itself by drawing energy from warm ocean water, eventually forming a clear, calm centre called the eye. Once hurricanes hit land, they lose their energy source and weaken rapidly.

Scientists measure hurricane strength using the Saffir Simpson Scale. Wind shear (different wind speeds at various heights) can either strengthen or weaken these storms.

Remember: Hurricanes are essentially giant heat engines powered by warm ocean water!

Hurricane Impacts and Plate Tectonics

Storm surge creates some of the worst hurricane damage - the low pressure literally raises sea level, pushing massive walls of water onto land. Long-term impacts include soil salinisation from flooding, which stops crops growing and devastates farming communities.

Switching to plate tectonics, you need to distinguish between oceanic and continental crust. Oceanic crust is younger (under 200 million years), denser, thinner $5-10km$, and gets destroyed through subduction. Continental crust is older (200+ million years), less dense, thicker $30-50km$, and permanent.

Plate boundaries create different landforms: fold mountains form where plates collide (like the Himalayas), conservative boundaries slide past each other (San Andreas Fault), and constructive boundaries pull apart, creating new crust (Iceland).

Radioactive decay in Earth's core drives convection currents, which power plate movement - it's like a massive underground heating system.

Key Point: Each plate boundary type creates different hazards and landforms - learn the examples!

Earthquakes and Volcanic Prediction

Earthquake effects depend on seven crucial factors: depth of focus, magnitude, distance from epicentre, location type, time of day, underlying geology, and liquefaction risk. A shallow earthquake in a busy city during rush hour will cause far more damage than a deep one in rural areas.

Scientists use two scales to measure earthquakes. The Mercalli scale $1-12$ describes intensity qualitatively, whilst moment magnitude $2.5-10$ uses seismographs to measure actual wave size quantitatively.

Hotspots occur when magma plumes rise through oceanic plates due to intraplate pressure - think Hawaii's volcanic chain.

Predicting volcanic eruptions involves multiple technologies: lasers detect swelling, pH changes show rising magma, gas analysis reveals sulphur content, and seismometers track earthquakes as magma moves. Tilt meters, ultrasound, and satellite imagery provide additional monitoring data.

Study Tip: Remember the seven earthquake factors - they're frequently tested and help explain why some quakes are more devastating than others!

Earthquake-Proofing and Volcanic Formation

Modern buildings use several earthquake-proofing techniques to save lives. Base isolation separates buildings from ground movement, whilst reinforced concrete and wider bases provide stability. Never build on unconsolidated rock, and education programmes (like Japan's awareness days) prepare communities for disasters.

Primary earthquake effects include collapsed buildings and liquefaction (when soil behaves like liquid). Secondary effects are often worse - fires, tsunamis, landslides, disease, famine, and economic damage can devastate regions for years.

Hazard mapping identifies high-risk areas and provides evacuation plans - it's like having a safety manual for entire regions.

Composite volcanoes form at destructive plate boundaries through a clear process. When oceanic and continental plates collide, the denser oceanic plate subducts and melts. Convection currents push this molten material upward, creating steep, cone-shaped volcanoes with explosive eruptions caused by viscous magma trapping gases.

Remember: Secondary effects of earthquakes often cause more damage than the initial shaking!

Wave Formation and Coastal Erosion

Wave size depends on three key factors: wind speed, how long the wind has blown, and fetch length (the distance wind travels over water). It's like building momentum - longer fetch and stronger winds create more powerful waves.

Constructive waves form in calm conditions with light winds and short fetches. Their stronger swash encourages deposition, creating wide, shallow beaches. Destructive waves result from strong winds and long fetches, with powerful backwash that erodes coastlines into narrow, steep beaches.

Wave formation starts when wind creates friction over the sea surface, producing swells. Energy causes water particles to rotate inside these swells, moving waves forward.

Coastal erosion happens through five main processes: wave pounding (sheer water force), hydraulic action (compressed air in cracks), abrasion (beach material acting like sandpaper), corrosion (chemical dissolving), and attrition (rocks hitting each other until they become sand).

Discordant coasts have different rock types, whilst concordant coasts have uniform geology.

Quick Tip: Think of destructive vs constructive waves like their names suggest - one destroys (erodes), one constructs (deposits)!

Coastal Landform Formation

The formation of stacks and arches follows a predictable sequence that's perfect for exam questions. Sea attacks small cracks using freeze-thaw weathering and hydraulic action. These cracks enlarge into caves, which eventually cut right through headlands to form arches. Continued erosion collapses arches, leaving isolated rock pillars called stacks, which finally erode down to stumps.

Longshore drift moves material along coastlines through a zigzag pattern. Waves hit beaches at angles, carrying sediment up and along the shore (swash), whilst backwash pulls material straight down due to gravity.

Material transport happens through saltation (bouncing), suspension (floating in water), and solution (dissolved chemicals).

Spit formation occurs when longshore drift carries sediment along the coast until it extends into open water. When wave energy decreases, deposition creates the spit structure. Wind and wave direction can form recurved ends, whilst the sheltered area behind often becomes a salt marsh.

Exam Tip: Learn the stack formation sequence - it's a classic 4-6 mark question that appears regularly!

Bars, Weathering, and Mass Movement

When spits grow across entire bays, connecting two headlands, they form bars. The trapped water behind becomes a lagoon that gradually fills with deposited sediment. A tombolo forms when a spit connects the mainland to an offshore island.

Weathering breaks down rocks in situ (in place) through physical, biological, and chemical processes. Freeze-thaw weathering occurs when water enters cracks, freezes and expands, then thaws repeatedly until rocks fracture. In warmer climates, salt crystal growth achieves similar results as evaporating seawater leaves expanding crystals in rock pores.

Biological weathering happens when plant roots grow in cracks (flora) or animals burrow through rock (fauna). Plant roots also produce humic acid that dissolves limestone.

Chemical weathering involves acid rain dissolving calcium carbonate rocks like limestone, producing calcium bicarbonate runoff.

Mass movement describes gravity-driven sediment movement: rockfall (freeze-thaw debris), mudflow (saturated soil), landslides, and rotational slip (curved soil slumping).

Remember: Weathering happens in place, whilst erosion involves movement - don't mix them up!

Sea Level Change and Climate Impact

Eustatic sea level change affects coastlines globally through several mechanisms. Glaciation locks water in ice sheets, lowering sea levels, whilst global warming causes thermal expansion and melting, raising them. Human activities accelerate this through greenhouse gas emissions, reducing the albedo effect (Earth's reflectivity).

Natural climate drivers include Milankovitch cycles (Earth's orbital changes), sunspot activity, volcanic dust blocking sunlight, and continental drift affecting ocean circulation patterns.

Rising sea levels shift wave-cut notch positions higher up cliffs. Less resistant coastlines experience accelerated erosion and retreat. Changing climate patterns bring more frequent storms and storm surges, whilst tropical storms can form further from the equator.

Submergence results from rising sea levels and/or land surface subsidence, fundamentally altering coastal landscapes.

Flood prediction relies on historical records identifying high-risk areas and meteorological forecasting. Prevention strategies include elevated building design, zoning regulations restricting development in flood-prone areas, and community education programmes covering evacuation procedures.

Climate Connection: Rising sea levels don't just cause flooding - they completely change how coastlines erode and evolve!