Does the Earth Smoke?

Vocabulary/new concepts:

Pyroclastic flow is a fast-moving, extremely hot, and highly destructive volcanic phenomenon. It is a mixture of hot toxic gases, ash, superheated volcanic rock, soot, and other pyroclastic materials that flows down the slopes of a volcano during its explosive eruption.

Magma is a hot mixture of molten rock lying beneath the earth’s surface.

Lava is when magma reaches the surface and exits the volcano.

Volcanic ash: small, fine particles of crushed rock, minerals, and glass that are ejected into the atmosphere during volcanic eruptions.

VOG (or volcanic smog) is a type of air pollution that is formed when sulphur dioxide (SO₂) and other pollutants released by volcanic activity chemically interact with atmospheric moisture, oxygen, dust, and sunlight.

Volcanoes: characteristics and manifestations

A volcano is a geological feature on the Earth’s surface. It occurs when superhot molten rock, called magma, rises from the earth’s mantle and erupts to the surface. The temperature of the magma at depth is between 600 °C and 870 °C, and it can rise to 1200–1300 °C as it rises to the surface due to oxidation processes resulting from contact with the atmosphere.

Volcanoes are usually found on tectonic plate boundaries or in areas where the Earth’s crust is relatively thin.

Tectonic plates are large, solid parts of the Earth’s lithosphere, which is the outermost layer of the planet. The lithosphere (also called the “mantle”) consists of the Earth’s crust and the uppermost part of the mantle. These plates fit together like a jigsaw puzzle and float on top of the semi-liquid asthenosphere beneath them—the uppermost part of the mantle.

The Earth’s surface is divided into several major tectonic plates as well as many smaller ones. These plates are in constant motion, albeit very slowly, at an average rate of a few centimeters per year. The movement of the tectonic plates is determined by the processes taking place in the Earth’s interior.

Figure 1. Map of the Earth’s 16 major tectonic plates Author. New maps of global geologic provinces and tectonic plates. American Institute of Physics – Phys.org. Retrieved March 27, 2023, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=130076176

When magma reaches the surface and comes out of the volcano during its eruption, it is called lava. The lava, along with gases and other materials, is ejected through holes in the Earth’s crust called vents. In the beginning, when lava erupts from the volcanic vent, its temperature is between 700 and 1200 °C. This eruption can be explosive, sending ash, rock, and gases high into the atmosphere, or it can be more effusive, with lava flowing steadily from side vents and fissures of the volcano along the lower parts of the topography and covering vast areas. Lava can travel tens of kilometres and spill directly into the ocean.

Figure 2. Plate tectonics. Endless cycle of carbon sequestration and release. Source: adapted from https://skepticalscience.com/volcanoes-and-global-warming.htm [accessed 01.02.2024]

Types of volcanoes

There are different types of volcanoes. They can have different shapes and sizes, being either conical mountains with a central vent, such as Mount Fuji in Japan or Mount Vesuvius in Italy, or they can form as fissures, where cracks in the earth’s crust allow lava to flow out over a large area, as seen in volcanic activity in Iceland.

Figure 3. Mount Fuji. Photograph taken in winter from a private plane at 28,000 feet at 1:30 p.m. on February 24, 2007. Public domain, https://commons.wikimedia.org/w/index.php?curid=1711534 

Figure 4. Vesuvius from a plane. Author: I, Pastorius, CC BY 2.5, https://commons.wikimedia.org/w/index.php?curid=2530370

Figure 5. A volcano in Iceland erupted on 3 August 2022, 40 km from the capital Reykjavik. Source: https://depositphotos.com/similar-images/593311418.html?qview=547424752

Impact of volcanic eruptions on Earth

Volcanic eruptions can have a significant impact on the Earth’s environment and population. They can release ash and toxic gases into the atmosphere, which can affect air quality and even the global climate. Volcanic eruptions can also cause pyroclastic flows, lahars (mudflows), and volcanic ash, which can lead to the destruction of landscapes and pose a risk to populations and settlements.

● A pyroclastic flow is a fast-moving, extremely hot, and highly destructive volcanic phenomenon. It is a mixture of hot gas, ash, volcanic rock, and other pyroclastic materials that flows down the slopes of a volcano during an explosive eruption. Pyroclastic flows are one of the most dangerous aspects of volcanic activity and pose a significant risk to human life and infrastructure. They can travel hundreds of kilometres and cause death through the super-heated gas that destroys the respiratory system. Pyroclastic flows are formed when a volcanic eruption releases huge amounts of gas, ash, and fragmented volcanic material into the atmosphere. Initially, these materials are ejected explosively, forming a dense, turbulent plume that rapidly descends the slopes of the volcano under the action of gravity. They can pass through pools of water and uplands and cause tsunamis.

● Lahar is a highly destructive type of mudflow or debris flow that occurs on the slopes of a volcano, usually triggered by volcanic activity. Lahars consist of a mixture of water, volcanic ash, rock, and other debris that can move rapidly down the slopes of a volcano, often following river valleys and channels. Lahars are usually caused by the melting of snow and ice on the volcano during its eruption or by the rapid mixing of volcanic ash and debris with water, for example, during heavy rainfall or the sudden release of a lake from a volcanic crater. The water combines with the loose volcanic material to form a thick slurry that cascades down with great force.

● Volcanic ash refers to small, fine particles of crushed rock, minerals, and glass that are ejected into the atmosphere during volcanic eruptions. It is formed when explosive volcanic activity breaks and pulverises solid volcanic material, such as lava and pyroclastic deposits, into small fragments.

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To download: Does the Earth smoke (presentation)

Are volcanoes harmful or beneficial?

Some of how a volcanic eruption can harm the planet are:

1. Gases. Volcanoes emit many gases during an eruption, including water vapour (_H2O), carbon dioxide (_CO2), sulphur dioxide (_SO2 ), hydrogen sulphide (_H2S), carbon monoxide (CO) and nitrogen oxides (NOX ). These gases can have direct and indirect impacts on air quality and climate. For example, sulphur dioxide can combine with water vapour in the atmosphere to form sulphate aerosols, which can affect visibility and contribute to the formation of acid rain.
2. Fine particulate matter. Volcanic eruptions release significant amounts of fine particles known as volcanic ash into the atmosphere. The size of these particles can range from microscopic to larger fragments. Volcanic ash can affect air quality by reducing visibility, causing respiratory problems when inhaled and settling on surfaces. Ash particles can also scatter and absorb sunlight, thereby affecting the temperature and climate of the atmosphere.
3. Volcanic smog (VOG). When volcanic emissions, especially sulphur dioxide, interact with sunlight, oxygen, and other atmospheric components, they can form a type of air pollution known as volcanic smog, or “VOG.” VOG contains aerosols of sulphuric acid and sulphates, which can have adverse effects on human health, especially for people with respiratory diseases.
4. Volatile organic compounds (VOCs). These compounds, such as methane and benzene, can contribute to the formation of ground-level ozone, a pollutant that can harm human health and vegetation.
5. Climate impact. Volcanic emissions can affect the Earth’s climate by introducing large amounts of gases and particles into the atmosphere. Sulphur dioxide, for example, can form sulphate aerosols that reflect sunlight into space, temporarily cooling the climate. In the process, plants die, crops are destroyed and animals that depend on these food resources suffer. Unlike volcanic emissions, greenhouse gases such as carbon dioxide contribute to long-term warming.

In addition to the negative consequences, it is important to note that volcanoes also have positive impacts; they play a significant role in shaping the earth’s surface and creating new lands –  islands, mountains, and plains. Over time, the accumulation of volcanic materials can form fertile soils, and volcanic activity can create unique ecosystems that support diverse plant and animal life.