Paper 1 Geography: Hazards, Ecosystems, and Coastal Landscapes

Natural Hazards Classification and Risk Factors

A natural hazard is defined as a natural event that has the potential to cause harm to people, property, and the environment. These hazards are generally classified into three distinct categories: tectonic, atmospheric, and geomorphological. Tectonic hazards involve movements of the Earth's crust, such as earthquakes and volcanic eruptions. Atmospheric hazards relate to weather and climate processes, including tropical storms, droughts, and heatwaves. Geomorphological hazards occur on the Earth's surface, such as landslides, mudflows, and avalanches.

The level of risk associated with these hazards is not uniform and is heavily influenced by several human and environmental factors. Poverty is a primary driver of risk, as people in lower-income regions often live in poorly constructed housing and lack the resources to evacuate or recover. Urbanization increases risk due to high population densities; when a hazard strikes a city, the potential for loss of life and infrastructure damage is significantly higher than in rural areas. Climate change acts as a risk multiplier, increasing the frequency and intensity of atmospheric hazards like floods and storms. Farming can also exacerbate risk, particularly when people settle on fertile but hazardous floodplains or volcanic slopes. Finally, preparedness, which includes the presence of early warning systems, evacuation plans, and public education, significantly determines whether a hazard event turns into a major disaster.

Global Distribution and Mechanisms of Tectonic Hazards

Earthquakes and volcanoes are not distributed randomly across the globe; they primarily occur in narrow bands along plate boundaries. Earthquakes are found at all types of plate margins, including constructive, destructive, and conservative boundaries. Significant concentrations are found around the "Ring of Fire" encircling the Pacific Ocean and along the Mid-Atlantic Ridge. Volcanoes are similarly concentrated at constructive and destructive margins but are generally absent at conservative margins and are also found at "hotspots" where magma breaks through a thin part of the crust.

Plate tectonics is the underlying theory explaining these movements. The Earth's lithosphere is divided into large plates that move due to convection currents in the mantle and slab pull. There are three main types of plate boundaries. At constructive (divergent) boundaries, plates move apart, allowing magma to rise from the mantle to create new crust, leading to shield volcanoes and gentle earthquakes. At destructive (convergent) boundaries, an oceanic plate is subducted beneath a continental plate or another oceanic plate; the friction and melting lead to powerful earthquakes and explosive composite volcanoes. At conservative (transform) boundaries, plates slide past each other in opposite directions or at different speeds; friction causes pressure to build up until it is released as a violent earthquake, though no volcanic activity occurs because no crust is being created or destroyed.

Comparative Case Studies: Chile ($2010$) and Nepal ($2015$)

The earthquake in Chile occurred on February $27$, $2010$, with a magnitude of $8.8$ on the Richter scale. It was caused by the subduction of the Nazca plate beneath the South American plate. Primary effects included the death of $500$ people and the destruction of $220000$ homes. Secondary effects were significant, including a tsunami that devastated coastal towns and fires at chemical plants. Immediate responses involved the rapid deployment of emergency services and the restoration of power to $90$ percent of the area within ten days. Long-term responses focused on a government-led reconstruction plan to rebuild houses without relying heavily on foreign aid, utilizing Chile's significant national wealth.

In contrast, the Nepal earthquake occurred on April $25$, $2015$, with a magnitude of $7.8$. This was caused by the collision of the Indo-Australian plate with the Eurasian plate. Primary effects were more devastating than in Chile, with nearly $9000$ deaths and over $7000$ schools destroyed. Secondary effects included massive landslides and avalanches, notably on Mount Everest, which killed $19$ people. Immediate responses were hampered by Nepal's mountainous terrain and lack of resources, requiring massive international aid from countries like India and China, including search and rescue teams and medical supplies. Long-term responses included the slow rebuilding of schools and heritage sites, with the economy suffering a loss of over $5$ billion US dollars, highlighting how lower national wealth leads to higher impacts and slower recovery.

Management of Tectonic Hazards and Global Atmospheric Circulation

People continue to live in tectonically active areas for various reasons, including the presence of fertile volcanic soils for farming, the availability of geothermal energy, tourism opportunities, or simply because they cannot afford to move. To mitigate the risks, authorities use the "Three Ps": Prediction, Planning, and Protection. Prediction involves monitoring seismic waves or gas emissions to provide warnings. Planning involves creating evacuation maps and emergency kits. Protection focuses on engineering, such as building earthquake-resistant structures with reinforced foundations and shock absorbers.

Global atmospheric circulation is the large-scale movement of air that distributes heat across the planet. It consists of three cells in each hemisphere: the Hadley, Ferrel, and Polar cells. Near the equator, air rises (low pressure), creating rainfall and tropical rainforests. At $30$ degrees north and south, air sinks (high pressure), creating dry conditions and deserts. This circulation also drives the distribution of tropical storms, which require sea temperatures above $27^{\circ}\text{C}$ to form, typically occurring between $5$ and $30$ degrees latitude where the Coriolis effect is strong enough to cause the storm to spin.

Tropical Storms and Climate Change: Typhoon Haiyan

Typhoon Haiyan struck the Philippines in November $2013$, becoming one of the strongest tropical storms ever recorded. The cause was a combination of very warm ocean water ($30^{\circ}\text{C}$) and low wind shear. Impacts were catastrophic: over $6300$ people died, primarily from a $5\,m$ storm surge. Approximately $90$ percent of Tacloban city was destroyed. Secondary impacts included power outages that lasted for months and the spread of disease due to contaminated water. As climate change continues, scientists predict that the frequency of the most intense storms (Category $4$ and $5$) will increase, and their distribution may move further from the equator as ocean temperatures rise.

Evidence for climate change includes historical temperature records, ice core data showing rising $CO_2$ levels, and the retreating of glaciers and ice sheets. Causes are split into natural and human factors. Natural causes include orbital changes (Milankovitch cycles), solar output variations, and volcanic eruptions that release ash to block sunlight. Human causes are dominated by the greenhouse effect, driven by the burning of fossil fuels, deforestation, and methane from farming. Management strategies involve mitigation, such as carbon capture and renewable energy to reduce emissions, and adaptation, which includes building flood defenses and developing drought-resistant crops.

Ecosystems, Biomes, and Tropical Rainforests

An ecosystem consists of biotic (living) and abiotic (non-living) components interacting in a specific area. Nutrients cycle through the system from the soil to plants (producers) and then to animals (consumers), eventually returning to the soil via decomposers. In a freshwater pond ecosystem, interdependence is clear: if the water becomes polluted (abiotic), the algae may die, which reduces food for small fish, subsequently impacting larger predators like herons. Global biomes, such as tropical rainforests, deserts, and tundra, are large-scale ecosystems defined by their climate and vegetation.

Tropical rainforests are characterized by high temperatures (average $27^{\circ}\text{C}$) and high annual rainfall (over $2000\,mm$). The soils are often latosols, which are nutrient-poor because high rainfall leaches minerals away. Vegetation is stratified into layers: the emergent layer, canopy, understory, and forest floor. Plant adaptations include buttress roots for stability and drip-tip leaves to shed heavy rain. Animals also adapt, such as the spider monkey's prehensile tail for life in the canopy. In the Amazon, deforestation is driven by cattle ranching ($80$ percent), commercial logging, and road building. This leads to habitat loss, soil erosion, and increased global warming through the loss of carbon sinks. Management involves selective logging, debt-for-nature swaps, and international hardwood agreements.

Hot Deserts and Desertification

Hot deserts have extreme climates with very low rainfall (less than $250\,mm$ per year) and high daytime temperatures. Desert soils are sandy and saline. Plants, like cacti, are xerophytic, meaning they have adaptations like thick waxy cuticles and water-storage tissues. Animals, like camels, have humps to store fat and can go long periods without water. Desertification is the process by which land becomes increasingly dry and degraded, losing its bodies of water and vegetation.

The causes of desertification include climate change leading to less rainfall, and human activities such as overgrazing, over-cultivation, and deforestation for fuelwood. These activities strip the soil of its protective cover, leading to wind and water erosion. The impacts include famine, loss of biodiversity, and migration. Solutions to desertification include the use of "magic stones" (stone lines) to reduce soil erosion and trap moisture, planting pits to concentrate water, and large-scale projects like the Great Green Wall across the Sahel region in Africa.

Coastal Processes, Landforms, and Management

Coastal landscapes are shaped by wave action. Constructive waves have a strong swash and weak backwash, depositing sediment to build beaches, whereas destructive waves have a weak swash and strong backwash, eroding the shoreline. Coastal processes include erosion (hydraulic action, abrasion, attrition, solution), transportation (longshore drift), and deposition. Weathering (such as freeze-thaw or salt weathering) and mass movement (such as slumping and rockfalls) also play roles in reshaping cliffs. Coastlines are categorized as concordant (parallel rock layers) or discordant (rock layers at right angles to the sea, forming bays and headlands).

Erosional landforms include cliffs, wave-cut platforms, caves, arches, stacks, and stumps. Depositional landforms include beaches, spits, bars, and sand dunes. Effective study requires the use of labelled diagrams to show the sequential formation of these features. Coastal management involves hard engineering, such as sea walls and groynes, which are expensive but highly effective at stopping erosion, and soft engineering, such as beach nourishment and dune regeneration, which are cheaper and more natural but require constant maintenance. Evaluating a case study involves weighing the high economic costs against the benefits of protecting housing and tourism, while considering the potential for "managed retreat," where areas of low value are allowed to flood to protect higher-value areas elsewhere.