Volcanic Activity (Leaving Cert Geography): Revision Notes

Human Interaction with Volcanoes

Humans have lived alongside volcanoes for thousands of years, learning to harness their benefits while managing their risks. This relationship between people and volcanic activity demonstrates how natural forces can both support and threaten human communities. Understanding these interactions helps us appreciate why millions of people choose to live in volcanic regions despite the potential dangers.

Positive effects of volcanic activity

Volcanic regions offer several significant advantages that have attracted human settlement throughout history. These benefits explain why some of the world's most densely populated areas are found near active volcanoes.

Creation of new land

Volcanic activity continuously creates new land through the cooling and solidification of lava flows. When molten rock reaches the surface, it cools rapidly to form basalt rock. Over extended periods, these layers accumulate and can eventually break through the ocean surface, forming entirely new islands.

This process shaped major landmasses we see today. Japan's entire archipelago formed approximately 60 million years ago through volcanic activity resulting from tectonic plate movement. The subduction of the Pacific Plate beneath the Eurasian Plate created the magma that built these islands over geological time.

More recently, in November 2013, underwater volcanic activity created a new island 1000 kilometres south of Tokyo. Although only 200 metres in diameter, this formation demonstrates how volcanic processes continue to generate new land. While ocean erosion may eventually wear away smaller formations, continued eruptions can help new islands become permanent additions to a nation's territory.

Iceland provides another excellent example of land creation through volcanic activity. This island nation formed 16-18 million years ago from basalt rock accumulation along the Mid-Atlantic Ridge. Iceland continues expanding today as the North American and Eurasian plates separate, while a hotspot beneath the island adds additional volcanic material to its landmass.

Development of fertile soils

Volcanic regions often feature some of the world's most productive agricultural land. This fertility results from the weathering of volcanic materials, particularly ash and tephra, which break down to release essential nutrients and minerals into the soil.

The area surrounding Mount Vesuvius in southern Italy demonstrates this agricultural benefit perfectly. Eruptions from this volcano have deposited thick layers of tephra across the Bay of Naples region. As this material weathered over time, it created exceptionally fertile soil that supports intensive farming throughout the year. Local farmers successfully grow vines, vegetables, fruits, and flowers, taking advantage of the nutrient-rich volcanic deposits.

However, this fertility has geographical limits. Areas located too far from volcanic sources lack these beneficial deposits, making crop cultivation much more challenging. The contrast between fertile volcanic soils and surrounding barren land clearly shows the agricultural advantages of volcanic activity.

Mount Merapi in Java, Indonesia, supports over one million people within 30 kilometres of its slopes precisely because of these fertile volcanic soils. The intensive rice cultivation possible in this region demonstrates how volcanic soil fertility can support dense population centres. Similarly, Hawaii's successful pineapple and sugar plantations operate on volcanic soils that provide the necessary nutrients for these crops.

Tourism opportunities

Volcanic landscapes have become increasingly popular tourist destinations, generating substantial economic benefits for local communities. This growth in 'volcanic tourism' accelerated after several well-publicised eruptions brought global attention to these dramatic natural phenomena.

Iceland exemplifies successful volcanic tourism development. Despite having over 130 active volcanoes, the country attracts approximately 600,000 tourists annually, earning €700 million from tourism activities. The 2010 Eyjafjallajökull eruption, while initially disruptive, ultimately increased international interest in Iceland's volcanic features.

Tourist activities in volcanic regions include hiking around volcanic mountains, taking sightseeing flights over volcanic craters, and cycling through volcanic landscapes. Many visitors are also drawn to volcanically heated waters, such as Iceland's Blue Lagoon Spa. These geothermal pools, heated by volcanic activity, maintain temperatures of 37-39°C and contain minerals like silica and sulphur that many people believe benefit their skin.

Yellowstone National Park in the United States attracts 3.6 million tourists yearly, drawn primarily by its geothermal features. The park sits above a 'super volcano' that creates numerous geysers and hot springs. Old Faithful, the park's most famous geyser, erupts every 45-110 minutes, shooting water and steam 35-55 metres high. These regular eruptions, lasting approximately four minutes each, provide visitors with predictable and spectacular natural displays.

Geothermal energy production

Regions with active volcanic activity can harness geothermal energy as a clean, renewable power source. This technology uses the intense heat generated by volcanic processes to produce electricity and provide heating for homes and businesses.

Iceland leads the world in geothermal energy utilisation. Magma rising through underground fissures heats surrounding rock formations, which in turn heat groundwater. This creates underground reservoirs of superheated water and steam that can be accessed through drilling.

The geothermal energy process involves several stages. Wells are drilled into heated rock formations where water temperatures exceed 200°C at depths around 1000 metres. Hot water is then pumped to the surface, where it decompresses and turns into steam. This steam powers turbines that generate electricity. After passing through the turbines, the steam moves to another facility where it heats water to 80°C for distribution to homes and businesses through central heating systems.

Currently, 25% of Iceland's electricity comes from geothermal sources, with 90% of homes and businesses heated using this volcanic energy. The Iceland Deep Drilling Project aims to increase geothermal electricity production to 50% by 2030 by accessing water heated to 450°C at greater depths.

Beyond electricity generation, Iceland uses geothermal energy for agricultural purposes. Approximately 50% of the heated water goes to greenhouses, enabling year-round cultivation of vegetables and fruits. An additional 26% supports potted plant production, while 24% supplies nurseries and forest plant cultivation.

Negative effects of volcanic activity

While volcanic regions offer many advantages, volcanic eruptions remain among nature's most dangerous phenomena. Understanding these risks helps explain the complex relationship between human communities and volcanic environments.

Loss of life

Volcanic eruptions can cause fatalities through both direct and indirect means. Direct deaths result from immediate volcanic hazards like lava flows, pyroclastic material, and toxic gases. Indirect deaths occur from secondary effects such as lahars, building collapses, and disease outbreaks.

Mount Sinabung in Indonesia demonstrates the sudden danger volcanic eruptions can pose. On 1st February 2014, this volcano erupted unexpectedly after a build-up of gas pressure. The eruption sent pyroclastic material over 1.5 kilometres into the sky before it fell back onto surrounding areas. Fifteen people within a 3-kilometre radius of the crater were killed by ash and lava as these materials flowed down the volcano's slopes.

Gas emissions from volcanic craters present another deadly hazard. In 1986, Lake Nyos in Cameroon released toxic gases that killed people in surrounding communities, demonstrating how volcanic dangers can extend far beyond visible lava flows.

Disruption to air travel

Volcanic eruptions can severely impact aviation by ejecting ash, dust, and other materials several kilometres into the atmosphere. This airborne material poses serious risks to aircraft engines, which can become clogged and fail when flying through volcanic ash clouds.

Airlines must cancel flights that would pass near potential ash clouds to ensure passenger safety. The 2010 eruption of Eyjafjallajökull in Iceland created one of the most significant air travel disruptions in aviation history. This eruption generated massive ash clouds that affected airspace across 20 countries, reaching an extraordinary height of 9 kilometres.

Flight disruptions lasted from 14th to 20th April 2010, forcing the cancellation of flights for over 8 million passengers. The widespread nature of this disruption demonstrated how a single volcanic eruption can have global consequences for international travel and commerce.