Satellites play a crucial role in monitoring volcanic hazards, offering a unique vantage point for observing volcanic activity and its impacts from space. They provide data on various aspects of volcanic eruptions, such as thermal anomalies indicating rising magma, gas emissions, and ash clouds. Satellites equipped with thermal imaging cameras can detect heat signatures from active volcanoes, often before an eruption becomes visible. This allows for early warnings and evacuation plans to be implemented. Additionally, satellites equipped with spectrometers can analyse volcanic gases, providing insights into the composition and quantity of gases like sulphur dioxide. This data is vital for assessing the potential climate impacts of eruptions. Furthermore, satellites are essential for tracking ash clouds, which is crucial for aviation safety. The ash can damage aircraft engines and reduce visibility, posing significant risks to air travel. By monitoring ash cloud movement, authorities can reroute flights to ensure safety. Satellite imagery also helps in assessing the aftermath of eruptions, including mapping lava flows and lahars, and evaluating environmental and property damage. This comprehensive monitoring is invaluable for disaster response and mitigation strategies.

Volcanic eruptions can have significant impacts on global climate, primarily through the injection of gases and ash into the atmosphere. The most notable effect is the cooling caused by sulphur dioxide (SO2), which converts to sulphate aerosols in the stratosphere. These aerosols reflect sunlight back into space, reducing the amount of solar radiation that reaches the Earth's surface. This can lead to a temporary global cooling effect. For example, the 1991 eruption of Mount Pinatubo in the Philippines led to a global temperature decrease of about 0.5°C over the following two years. Additionally, volcanic ash can also have a short-term cooling effect by blocking sunlight. However, in contrast, carbon dioxide released during eruptions can contribute to the greenhouse effect, potentially causing long-term warming, although this impact is relatively small compared to human-made CO2 emissions. The study of volcanic impacts on climate is a critical part of understanding natural climate variability, helping differentiate natural influences from human-induced climate change.

Volcanic eruptions can have profound long-term ecological impacts, shaping and altering ecosystems in several ways. Firstly, lava flows and pyroclastic deposits can destroy habitats, causing an immediate loss of flora and fauna. However, in the long run, these deposits can create new landforms and soils, which might eventually lead to the development of unique ecosystems. Secondly, volcanic ash can enrich soils with minerals, enhancing their fertility over time, which can benefit agricultural activities post-eruption. However, heavy ash fall can initially smother vegetation and disrupt photosynthesis, leading to a temporary decline in plant life. Thirdly, the introduction of new elements and compounds into the environment can lead to chemical changes in soil and water bodies, sometimes creating harsh conditions for existing species but also opening niches for new species to thrive. Additionally, volcanic eruptions can lead to climate changes due to the release of volcanic gases like sulphur dioxide, which can impact ecosystems indirectly by altering weather patterns and temperatures. These ecological changes underscore the importance of understanding the environmental consequences of volcanic activity in the context of conservation and habitat management.

Volcanic gases are a significant aspect of volcanic hazards, often overlooked compared to the more visible threats like lava flows and ash clouds. These gases, predominantly water vapour, carbon dioxide, sulphur dioxide, hydrogen sulphide, and hydrogen chloride, can have far-reaching impacts both close to the volcano and at a global scale. Near the volcano, these gases can be lethal, as they displace oxygen and lead to asphyxiation, or cause respiratory issues, skin irritation, and eye problems. Sulphur dioxide, in particular, can lead to acid rain formation, causing environmental damage and affecting water quality. Additionally, the release of large quantities of volcanic gases into the atmosphere can influence climate patterns. For instance, sulphur dioxide can lead to the formation of sulphate aerosols, which reflect solar radiation and can cause temporary global cooling, as evidenced by the eruption of Mount Pinatubo in 1991. The study of these gases is crucial for hazard assessment and mitigation, especially in densely populated regions near volcanoes.

Predicting volcanic eruptions is a complex but increasingly feasible task, involving the integration of various geological, geophysical, and geochemical monitoring techniques. One of the primary methods is the analysis of seismic activity. Most volcanic eruptions are preceded by an increase in seismicity, including small earthquakes and tremors, which indicate the movement of magma beneath the volcano. Seismographs are used to detect and analyse these seismic patterns. Another method involves ground deformation monitoring, which detects swelling or sinking of the volcano's surface, suggesting magma accumulation or movement. This is achieved using instruments like tiltmeters, GPS, and InSAR (Interferometric Synthetic Aperture Radar) technology.

Geochemical monitoring, which involves analysing volcanic gases and thermal springs, also provides critical clues. An increase in gas emissions, particularly sulphur dioxide, is often a sign of rising magma. Additionally, changes in the composition of gases can indicate changes in the magma chamber's conditions.

Remote sensing techniques, including satellite observations, are increasingly used to detect thermal anomalies and gas emissions from space, providing a broader, real-time view of volcanic activity.

Despite these advancements, predicting the exact timing and size of an eruption remains challenging. Volcanic systems are complex, and not all signs of unrest lead to an eruption. Thus, while scientists can often forecast an increased likelihood of an eruption, the precision of these predictions varies. Continuous monitoring and research are essential for improving prediction capabilities, contributing significantly to risk management and evacuation planning in vulnerable areas.