IELTS Academic Reading Practice Test 64

Between the late eighth and eleventh centuries, Norse sailors from Scandinavia established settlements across the North Atlantic, travelling to Britain, Ireland, Iceland, Greenland and eventually Newfoundland. These voyages were not random acts of bravery. They required reliable methods of finding direction at sea, often far from any coastline and frequently in poor weather. The sailors possessed no magnetic compass; that instrument, developed in China, did not reach European waters until later. Instead they combined observation of the sun and stars with a detailed understanding of wind, waves, birds and other natural signs. Their approach was not written down but was passed from one generation to the next by word of mouth.

For most everyday journeys, coastal navigation was sufficient. Sailors followed the shape of the shore, watched for distinctive cliffs, islands and river mouths, and used simple landmarks to check their position. Aids such as cairns and beacons may have marked some routes. The sagas describe voyages that moved in short stages along the Norwegian coast, from harbour to harbour, before setting out across open water. This kind of sailing demanded excellent local knowledge rather than any instrument, and in clear weather a familiar mountain could be recognised from a considerable distance.

In the open ocean, the sun was the primary reference. Norse navigators probably used a bearing dial, a device based on the shadow cast by a central pin. A fragment of a wooden disc, discovered in Greenland in the mid-twentieth century and known as the Uunartoq disc, has been interpreted by some archaeologists as part of such a sun compass. The disc carries marks that may correspond to points on the horizon or to annual changes in the sun's path. By aligning the disc with compass directions and reading the shadow, a helmsman could hold a chosen course when the sun was visible.

Cloudy skies presented an obvious problem, and this is where the so-called sunstone may have been used. The sagas mention a stone that allowed a navigator to find the sun even when the sky was overcast. Scholars have suggested that certain transparent crystals, such as Iceland spar, a form of calcite, can be used to locate the sun because they split light into two beams, a property known as double refraction. By rotating the crystal and observing the changing brightness of the two images, a practised user could determine the direction of the sun behind the clouds. Direct archaeological evidence is scarce, but experiments have shown that the technique works.

At night, particularly in northern latitudes, the stars offered another guide. The Norsemen knew how to locate the North Star, which remains almost fixed in the sky, and used its height above the horizon to estimate how far north or south they had travelled. In the far north, summer nights are short or entirely absent, so stellar navigation was less useful during the main sailing season. During the long winter nights it may have mattered more, although few captains would willingly risk open water in winter storms.

Natural signs of land were also vital. Norse sailors watched for sea birds returning to their nests in the evening, and released ravens to detect islands beyond the horizon, a practice attributed to the explorer Flóki Vilgerðarson. Whales and seals could indicate productive fishing grounds rather than land, but their behaviour sometimes betrayed the presence of a coast. A change in the colour of the sea, floating seaweed or drifting timber could all signal that land was near. Such observations were especially valuable in fog, when celestial methods failed.

The sea itself carried information. Experienced navigators read the direction and size of ocean swells, which are produced by distant storms and travel across great distances. Passing near an island can reflect or bend waves, creating a confused pattern that a skilled helmsman could feel through the steering oar. Currents, such as those that flow around Iceland and along the Greenland coast, were learned through repeated voyages. The glow of an ice field, called ice blink, could be seen on the horizon long before the ice itself appeared. These signs were unreliable on a first voyage, but on familiar routes they provided a continuous record of position.

Seasonal timing was also part of the system. North Atlantic crossings were normally attempted only in summer, when daylight was long and the weather less dangerous. Winter brought storms, ice and prolonged darkness, so ships were laid up and voyages postponed. The length of a voyage was estimated from remembered distances and from the number of days at sea, an inexact measure that nevertheless allowed a captain to know when land should be near. If no land appeared, the safest response was to turn back along the known route.

Norse navigation was therefore not a single instrument but a whole set of skills and observations. It was well suited to the conditions of the North Atlantic, and it allowed small open vessels to make repeated, regular crossings. Although modern navigators rely on satellites and precise charts, the Viking achievement remains a remarkable example of human observation applied to one of the world's most difficult environments.

Iceland owes its geothermal wealth to its unusual geology. The island lies across the Mid-Atlantic Ridge, where the Eurasian and North American tectonic plates are moving apart, and it is one of the few places on Earth where the deep ocean floor rises above sea level. Volcanic activity is widespread, and magma lies relatively close to the surface. As rainwater and meltwater percolate down through cracked basalt, they are heated by these hot rocks and often return to the surface as steam or hot springs. Because the plates spread slowly, fissures and faults allow water to circulate deeply, and the rock is unusually young and permeable. This geothermal gradient means that heat can be reached at depths that are economically drillable, an advantage that few other countries share.

People have used this natural heat since the island was first settled in the ninth century. Early Icelanders bathed in hot springs and used them for washing clothes, and medieval records mention pools where communities gathered. For centuries, however, geothermal energy remained a small-scale convenience rather than a source of power. Before the Second World War, the naturally rising hot water could not be distributed over long distances because it cooled too quickly. The first attempts to pump hot water for heating began in the Reykjavík area in the early twentieth century, but the real change came after the war, when improvements in drilling and pipe technology made it possible to transport hot water over considerable distances.

Today the most visible use of geothermal energy is in district heating. Boreholes are drilled into high-temperature fields near the capital, and the hot water or steam is piped to homes, schools, hospitals and businesses. Once cooled, excess water is returned to the ground through reinjection wells. District heating systems now supply the great majority of Icelandic households, replacing oil and coal heating in most urban areas. The result has been a dramatic improvement in urban air quality, since burning fossil fuels in individual homes was one of the main sources of winter smoke. The shift required large public investment, but it has protected consumers from fluctuations in fuel prices and has reduced the country's dependence on imported energy.

Geothermal energy also produces electricity. Iceland's hydroelectric stations generate most of the country's power, but geothermal plants provide a significant and growing share, and they have the advantage of not depending on rainfall. Steam from deep wells drives turbines at plants such as Hellisheiði, on the outskirts of Reykjavík, and Nesjavellir, in the Hengill volcanic area. Hellisheiði, a combined heat and power station, is among the largest geothermal plants in the world. Geothermal reservoirs must be managed sustainably, because over-extraction can cool the rocks and reduce output over decades, so operators carefully monitor underground temperatures and pressure. When managed carefully, the resource is renewable on a human timescale, and geothermal electricity can operate almost continuously.

Beyond heating and power, geothermal resources support a range of economic activities. Hot water is used in greenhouses to grow tomatoes, cucumbers and flowers, which is remarkable at a latitude where outdoor growing seasons are short. Fish farms use warm water to speed the growth of young fish, and many towns keep streets and pavements clear of snow with pipes laid beneath them. Swimming pools, which are an important part of Icelandic culture, are heated geothermally. In addition, the reliable hot water supply has encouraged businesses that need controlled temperatures, such as drying facilities for fish and wood. One of the country's most famous tourist attractions, the Blue Lagoon, is fed by mineral-rich water released from the Svartsengi geothermal plant, and its appearance was an unintended side effect of power production.

Geothermal power is not free of environmental problems. Some high-temperature fields release hydrogen sulfide, a gas with a noticeable smell of rotten eggs, and this occasionally causes complaints in nearby communities. A more serious technical challenge is the falling pressure that can occur in underground reservoirs if more fluid is withdrawn than is naturally replaced. Operators therefore monitor wells closely and reinject treated water to maintain pressure. Compared with burning coal or oil, these emissions are minor, but they still need to be controlled, and local sensitivity to odour has led to improved gas scrubbing systems. Although the amount of greenhouse gas released per unit of electricity is far lower than for fossil fuels, geothermal plants still require careful management to remain sustainable.

Research is pushing the technology further. Engineers have drilled experimental wells to depths of several kilometres, where temperatures exceed 400 degrees Celsius and the energy available from each well is much greater. Icelandic scientists have also developed a method known as CarbFix, in which carbon dioxide dissolved in water is pumped into porous basalt and reacts with the rock to form solid carbonate minerals. This process, which imitates natural weathering but speeds it up, has attracted international attention as a possible way of permanently storing carbon. The success of CarbFix has led to experimental projects elsewhere, and it illustrates how geothermal resources can be used not only for energy but also for environmental protection.

Iceland's experience is now exported. Icelandic companies and consultants work on geothermal projects in countries that have similar volcanic geology, helping to build district heating systems and power plants. The Icelandic government has supported training programmes for engineers and technicians from other nations, and visitors regularly come to study how a small island transformed its energy system. The main lesson is that geothermal development requires large upfront costs, careful mapping of underground resources and long-term political commitment. As more countries search for stable low-carbon sources of electricity and heat, Iceland's long experiment with geothermal energy offers both a model and a warning about the need for patient investment and careful resource management.

One of the largest population movements in human history is the shift from countryside to city. The United Nations estimates that more than half of the world's people now live in urban areas, and this proportion is still rising. Behind this statistic lie hundreds of millions of personal decisions. Some people leave rural areas to escape poverty, conflict or a changing climate; others are attracted by better jobs, schooling and services. Public discussion often treats this migration as either an engine of opportunity or a recipe for overcrowding. In my view, such blanket judgements are misleading. The real question is how cities manage growth.

Rural communities push people out for reasons that are difficult to separate. In many agricultural regions, land is divided into plots too small to support a family, and crop prices are unstable. Environmental pressures, including drought and soil degradation, add to the strain. At the same time, cities pull people in. Urban labour markets are larger and more varied, offering work in manufacturing, construction, retail and services. Even a first job that is informal and poorly paid often brings a more reliable income than farming. Young people may also see the city as a place to continue their education and learn new skills.

The money sent home by migrants, known as remittances, is one of the clearest benefits of this movement. In many low- and middle-income countries, remittances exceed foreign development aid and are a vital source of income for rural households. Families use the money to buy food, pay school fees, build houses and start small businesses. Because it goes directly to households, it reaches places that formal aid often misses. Critics sometimes argue that remittances create dependency, but the evidence suggests that they more often reduce poverty and improve children's education.

Economists also point to the productivity gains that arise when workers and firms concentrate in one place, a phenomenon known as agglomeration economies. A city business can share suppliers, recruit from a deeper pool of skilled workers and learn quickly from competitors and customers. These advantages lower costs and encourage innovation. They help to explain why cities remain attractive even when rents and wages are high: the benefits of proximity frequently outweigh the costs. This is not automatic, however. Poor transport, scarce housing and burdensome regulations can erase the gains.

The difficulties of rapid urban growth are real and often severe. Housing construction rarely keeps pace with new arrivals, so many migrants settle in informal neighbourhoods with inadequate water, sanitation and electricity. Roads become congested, and schools and clinics are overcrowded. In such conditions, the gains that brought people to the city can be undermined. Poor families spend a large share of their income on rent and commuting, and the risk of injury or illness increases. Public services, if built after the fact, cost more than they would if planned in advance.

Population density, however, does not have to lead to greater environmental damage. Compact cities can use land, energy and materials more efficiently than sprawling low-density settlements. Buildings share walls, reducing the energy needed for heating and cooling; public transport becomes viable; and services such as waste collection are cheaper to provide per household. By contrast, suburban growth that depends on private cars tends to increase emissions and destroy farmland. The environmental outcome therefore depends less on whether people live in cities than on how those cities are designed.

Social integration is another important variable. New arrivals are often blamed for increases in crime and pressure on public housing, but studies of migrant neighbourhoods show that they can strengthen urban life by opening businesses, filling labour shortages and supporting older residents. Where integration fails, it is usually because governments have underinvested in affordable housing, language classes and anti-discrimination laws. A city that treats migrants as temporary workers will struggle; a city that treats them as future citizens is more likely to benefit from their energy and enterprise.

Some commentators call for restrictions on rural-to-urban migration, arguing that cities are already too big to be manageable. I find this advice unpersuasive. Attempts to stop migration rarely work; they simply push people into informal settlements and unprotected work. More importantly, a ban would ignore the wider benefits that migration brings to both migrants and the places they leave. The sensible response is not to close city gates but to plan for growth, by investing in public transport and utilities, reforming land markets and supporting labour rights.

Migration also transforms rural areas. When young people leave, villages can lose workers and schools, but they also receive remittances and ideas. Returning migrants often bring savings, skills and contacts, and they may invest in local businesses or introduce new farming methods. Rural decline is not inevitable; it is made worse by policies that concentrate public services in cities and neglect rural roads, electricity and internet access. A balanced strategy would improve conditions in the countryside while accepting that many people will still choose urban life.

In the end, the movement of people into cities is not a temporary problem to be solved but a long-term reality to be managed. Cities can become engines of opportunity if they are planned, funded and governed well; they can also become centres of poverty and pollution if growth is ignored. The difference lies not in migration itself but in the decisions of governments, employers and citizens.