Volcanoes are among the most influential forces of nature on Earth. They produce many types of hazards that can harm people and change the landscape. They also emit chemicals into the atmosphere, lithosphere and hydrosphere. These chemicals are part of the Earth’s chemical cycle.
The Biogeochemical Cycle
The Earth can be split up into two compartments: the biotic compartment and the abiotic compartment. The biotic compartment encompasses the biosphere, which is the sum of all living things. The abiotic compartment is made up of the lithosphere (crust), hydrosphere (oceans, rivers and lakes) and the atmosphere. Volcanoes play an important role in how chemicals and elements are recycled. In other words, volcanoes play an important role in the biogeochemical cycle of the Earth.
There are six cycles in the biogeochemical cycles that volcanoes impact:
- Carbon cycle
- Hydrogen cycle
- Nitrogen Cycle
- Oxygen Cycle
- Phosphorus Cycle
- Sulfur Cycle
- Water Cycle
Volcanic activities melt and create the lithosphere, emit gases into the atmosphere, and emit solids and gases into oceans. All the chemicals listed above, plus many more trace chemicals, are recycled through the abiotic compartment because of these volcanic activities.
The Role of Volcanoes in the Chemical Cycle of the Lithosphere
Volcanoes recycle chemicals in the lithosphere through activity at subduction zones. Subduction zones occur at plate boundaries where an oceanic plate is subducted underneath a continental plate. The weight of the water-saturated crust causes the oceanic plate be more dense than the continental plate. As the oceanic plate is buried, it melts within the mantle to form magma. This magma contains all the chemicals that were within the oceanic plate and it erupts through volcanoes at the surface.
Studying the chemical composition of igneous rocks erupted from these volcanoes confirms that the primary elements in these rocks are silicon and oxygen. These elements are also the most common in the Earth’s crust, which makes sense since the magma came from melted oceanic crust.
The Role of Volcanoes in the Chemical Cycle of the Atmosphere
Whether through large eruptions or through small events of passive degassing, volcanoes play a key role in injecting chemicals into the atmosphere. Large eruptions inject large amounts of carbon and sulfur dioxide gas high into the atmosphere. Passively degassing volcanoes are persistent emitters of these gases. Other gases injected into the atmosphere include the elements hydrogen, chlorine and fluorine.
The main gases that are emitted by volcanic activity – sulfur dioxide, carbon dioxide and water vapor – are also greenhouse gases that can cause global warming. For this reason, volcanoes have the potential to change the climate in the same way that anthropogenic pollution does. In fact, after some major volcanic eruptions, such as Mt. Pinatubo Volcano in 1991, climate researchers have recorded short-term changes in the Earth’s climate.
The Role of Volcanoes in the Chemical Cycle of the Hydrosphere
At plate boundaries below the ocean where plates are splitting apart, magma and magmatic gases are injected directly into ocean water. Because of the interaction of cold sea water with hot magma and gases, a lot of chemical reactions occur. Many of these reactions produce particles that are made up of molecules containing sulfur, iron, magnesium, zinc, copper, and many more elements. The deposition of these particles around the area of expulsion is what creates chimney structures called “black smokers”.
Magma is the source of all the elements on the planet except those brought by meteorites. There will never be more or less of these elements and they are only recycled through volcanic processes. By far the largest point source of volcanic activity’s role in the chemical cycle is the emission of gases into the atmosphere.
Related Articles:
Volcanoes are Natural Polluters
Subduction Zone Volcanoes of the United States
Sources:
Marc J. Defant & Mark S. Drummond, 1990. "Derivation of some modern arc magmas by melting of young subducted lithosphere," Nature, 347; 662-665.
M. M. Halmer, H. -U. Schmincke and H. -F. Graf, 2002. "The annual volcanic gas input into the atmosphere, in particular into the stratosphere: a global data set for the past 100 years." Journal of Volcanology and Geothermal Research, 115; 511-528.
Hydrothermal Venting, Noaa.gov. Accessed April 2010.
Alexandra Matiella Novak - With a PhD in Geology and expertise in science education, Alexandra is passionate about increasing the public's Earth science literacy.
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