The force with the most powerful potential on earth is found within it. The earth is getting hotter with depth, reaching about 7000°C in the center of its core which is hotter than the surface of the sun. This heat which is generated from the decay of radioactive materials in the core, heats the rocky surrounding layer called the mantle. The heat creates a movement in the mantle which causes a movement of the earth’s crust (the surface of the earth which is the layer above the mantle). The crust is not a continuance shell but is built of giant pieces called tectonic plates, and the mantle movement causes these plates to move.
The plates’ movement involves several types of interactions between them with several different geological outcomes. Two of them involve volcanism:
Plates Divergence – Is when two plates diverge from one another due the mentioned movement in the mantle. This movement also causes hot material from the mantle to rise and as it does, this rocky material melts creating magma (molten rock). The magma emerges through the crack that was formed by the separation of the two plates and fills it. When the magma reaches the surface of the earth it is called lava.
An example for tectonic plates divergence, is a mid-oceanic ridge, such as the Mid-Atlantic Ridge, which contains volcanoes caused by divergent tectonic plates pulling apart.
Plate Convergence – Is when two plates are moving towards each other. When the two plates are continental ones they collide creating mountains, but when an oceanic plate meets another oceanic plate or a continental plate, it moves beneath it creating what is called a subduction zone.
The sinking oceanic plate is full of water and when it reaches a certain depth, this water lowers the melting point of the surrounding solid mantle (a process called flux melting), which creates magma (molten rock). This magma, hotter and less dense than the surrounding rocks, rises up towards the surface and erupts as an intense volcano.
An example for tectonic plates convergence, and probably the most interesting and relevant area for our mission, is the volcanoes in the Ring of Fire which encircle the basin of the Pacific Ocean.
There is another volcanic activity, which is not caused by the tectonic plates movement (and so doesn’t form next to tectonic plates interaction) called a HOTSPOT. In this case hot material rises fast from the deep mantle or even the core-mantle boundary, towards the earth’s crust. This hot mantle plume is so intense that it burns a hole in the crust and tremendous volumes of lava erupt.
The most famous Hotspots on earth are the state of Hawaii, a group of islands which are acutely volcanoes and the Yellowstone volcano in Wyoming USA.
There are around 1510 active volcanoes in the world. About 75% of them are located in the mentioned Ring of Fire since the Pacific Ocean basin is comprised of active tectonic plate boundaries.
As powerful as volcanic eruptions are, it is not the destruction potential held by the bursting but rather the global climatic aftereffect that is relevant.
The desirable worldwide impact of an eruption is largely the result of the gases release. It appears that eruptions of global effects, at first lead to an instant cooling period and then to a warming period.
The global cooling is a result of global dimming, which is caused mostly by sulfur compounds that are released from the volcano to the atmosphere and simply block the sun. The warming effect that follows is caused mostly by the CO2 gas that is released during the eruption and acts as greenhouse gas.
The reason that the warming effect follows the cooling period even though the effecting compounds are released at the same time, is that the sulfuric compounds stay in the atmosphere for a limited time while CO2 stays in the atmosphere and accumulates.
The Indian volcanic outburst can set as an example for the global destructive potential of volcanism, as some scientists claim today, it caused the extinction of the dinosaurs around 65 million years ago, and not an asteroid hit which its impact was only the trigger that set off a volcanic outburst which was the main element that drove to the extinction of almost 75% of the species alive at that time.
Approximately 251 million years ago, the vastest extinction known to paleontology had occurred when up to 95% of all species had gone extinct. This unprecedented proportion of extinction is largely ascribed to a volcanic event called the Siberian Flood Basalts during which vast quantities of magma and gases were poured out of a chain of volcanoes in Siberia. The Siberian eruption presumably contributed at first to an enormous cooling effect (caused by sulfur dioxide emission) and then to global warming (due to greenhouse gases as CO2). Most of the species were probably killed at that phase. Since the water temperature rose gently, marine creatures lived relatively calmly. But only until the seas released their frozen methane (for further explanation please read Methane Hydrates) and there was massive extinction of species from the world's oceans.
The volume of lava that erupted in Siberia, is thought to have been about 2 million cubic kilometers (480,000 cubic miles), but volcanic activities don’t have to involve such huge volumes of lava to cause such a strong impact. There is a second type of volcanic activity, more of an explosive one (in comparison to the flood type as the Siberian eruption) that is known to affect the entire planet. They are called ultra Plinian eruptions, and they erupt from what are known as super volcanoes.
The nature of volcanic eruptions is determined by the magma that forms it, which is determined mostly by its chemical composition. The type of magma that generates Plinian eruptions is called Rhyolitic magma, and is characterized by High SiO2 (silica) content (about 65-75%), comparatively lower temperature (650 - 800°C) and high viscosity which keeps the gases in, not allowing them to escape (as with basaltic magma) and so holds high amounts of gases within the magma.
The composition of the gases in the Rhyolitic magma is mostly H2O (water vapor) and some CO2 (carbon dioxide) as well as Sulfur, Chlorine, and Fluorine gases.
An Ultra Plinian eruption occurs after the pressurized magma (which builds over time as more magma collects under the enormous weight of overlying rock) raises overlying crust, enough to create vertical fractures that extend to the planet's surface.
As pressure is reduced the volume of gas expands, making the magma burst in an explosive way (inside the magma chamber the gas is dissolved in the liquid, but when pressure is decreased as magma rises toward the surface of the earth, the gas forms a separate vapor phase, just like a shaken bottle of soda as it is opened).
Ultra Plinian eruptions are apparently the largest, most destructive kinds of eruptions on Earth. They are marked by the ejection of large amount of ash at hundreds of feet per second and very powerful continuous gas blast eruptions that rise as a massive column, as high as 30 miles (48 km), into the atmosphere. The force of a single super volcanic explosion, which propels this column of gas and ash sky-high, is million times stronger than the Hiroshima nuclear bomb.
This kind of an eruption would erase virtually all life within a radius of hundreds of kilometers from the site and entire continental regions further out can be buried meters deep in ash, as tremendous currents of superheated gas and rock flow down from the volcano called pyroclastic flows, along with toxic particles spread, and acid rain falls after Hydrochloric acid condenses with water vapor. But of course what we are interested in is their severe global impacts, and in what is referred to as their "cataclysmic effect on life".
The world-wide effects occur when the eruption is powerful enough to reach the stratosphere (the second layer of the atmosphere) because in the first layer (the troposphere) rain clouds continually form and rain so that the sun blocking material gets washed out by the rain after a short period of time. Sulfur dioxide (SO2) is one of the two most significant components of Ultra Plinian eruptions, and of the varied other gases that make up the eruption, it causes the strongest immediate effect on the environment (as oppose to CO2 which will cause a very strong effect in the long run). Sulfur dioxide reacts with oxygen and water to produce tiny droplets of sulfuric acid (H2SO4) which condenses rapidly in the stratosphere and reflect sunlight directly back into space. Stratospheric winds spread the sulfuric acid particles until they practically cover the globe, where they can linger for a couple of years. By reflecting the sunlight, they reduce the amount of energy reaching the lower atmosphere and so the earth's surface is getting cooler.
About 74,000 years ago, the Toba eruption in Indonesia led to such global cooling that caused massive population reduction among animals all over the planet. The eruption column, tens of kilometers high, spouted billions of tons of ash and gases into the stratosphere which quickly scattered all across the globe. The Billions of tons of sulfuric acid caused a yellow haze that clothed the planet for about 6 years, blocking the sun's radiation, causing a complete deforestation in Southeast Asia and cooling of sea temperatures by 3–3.5°C. The eruption caused an instant Ice Age on Earth (some scientists claim it accelerated one by accelerating the glaciers expansion) so even after the sulfuric acid cloud was scattered the ice cover reflected back the sun radiation (for more information about sun radiation reflection please read our article called Albedo). The Toba eruption drove the Earth into what is called a volcanic winter. On the whole, average global temperatures were reduced by 5 to 15°C.
"It was like flipping the switch on the global climate system from hot to cold" said Michael Rampino, Professor of Earth and Environmental Sciences.
One recent example for eruptions’ climatic effect is the 1991 eruption of Mount Pinatubo in the Philippines. The eruption injected nearly 20 million tons of SO2 into the stratosphere that spread around the globe in about 3 weeks. The recorded effect was a 0.5°C (0.9°F) drop in temperature for the following two years. It might sound like a small temperature decrease, but as for global average it is considered significant, especially in a climate system like the earth’s that is highly dominated by positive feedbacks so that even the slightest temperature change can affect entire weather systems. One year after the eruption, the U.S. experienced its third coldest and wettest summer in 77 years, and major flooding of the Mississippi River occurred. These observations are consistent with predictions made by climate models of Pinatubo’s effect.
The much larger eruption of Tambora, Indonesia, in 1815 produced the greatest volcanic effects on climate in recorded history, with a 1°C (1.8°F) global temperature decrease. Even in Europe, over the other side of the globe, that year was referred as “the year without a summer.”
Super volcano eruptions would release thousands of times more energy than the Pinatubo and Tambora eruptions. The 5 to 15°C decrease in global temperature attributed to super volcano eruptions is enough to have a major impact on the climate, and ecosystems.
Under natural conditions only about 1% of the magma beneath volcanoes is estimated to ever burst to the surface of the earth. Since much more magma is already there, there may be processes that can not only trigger an eruption but also intensify it.
Cracking of the earth’s crust might influence the magma's dynamics. New cracks allow, otherwise trapped magma, to flow from the deep or to extract heat and boost the upwards flow of magma.
It is said that intense and severe seismic activity (earthquakes) might lead to the cracking of the crust. There are geologists who argue that severe seismic activity can trigger and intensify an eruption by allowing more magma to escape from deep within the planet. Underground explosions can generate seismic waves. This technique is in use for decades for research purposes, at low magnitude and with caution, there are actual machines that are designed for that. Deeply buried large amount of explosives, several kilometers down (modern drilling equipment can reach thousands of meters below the earth’s surface) at the right spots along the planet’s crust, seems like an idea worth exploring.
It seems likely that with the right amount of geological research and tools, a way to unleash this enormous force can be found or maybe while exploring this topic, new and more interesting phenomena over the 510,065,000 square kilometer surface of the earth, below it or above it, would be found.