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105-634: The Big Dan Shear Zone was contemporaneous to volcanism due to the higher density of felsic dikes situated at the shear zone. These dikes are only present north of the Link Lake Deformation Zone , therefore they may be subvolcanic feeders to the felsic lava flows to the south. Renewed tectonism along the Big Dan Shear Zone displaced sediments east of the Ontario Northland Railway . This phase of tectonic activity along

210-467: A discharge tube allowed researchers to study the emission spectrum of the captured particles, and ultimately proved that alpha particles are helium nuclei. Other experiments showed beta radiation, resulting from decay and cathode rays , were high-speed electrons . Likewise, gamma radiation and X-rays were found to be high-energy electromagnetic radiation . The relationship between the types of decays also began to be examined: For example, gamma decay

315-787: A mid-ocean ridge , such as the Mid-Atlantic Ridge , has volcanoes caused by divergent tectonic plates whereas the Pacific Ring of Fire has volcanoes caused by convergent tectonic plates. Volcanoes can also form where there is stretching and thinning of the crust's plates, such as in the East African Rift and the Wells Gray-Clearwater volcanic field and Rio Grande rift in North America. Volcanism away from plate boundaries has been postulated to arise from upwelling diapirs from

420-410: A billion years. This Ontario location article is a stub . You can help Misplaced Pages by expanding it . This article about a specific Canadian geological feature is a stub . You can help Misplaced Pages by expanding it . This article about structural geology is a stub . You can help Misplaced Pages by expanding it . Volcanism Volcanism , vulcanism , volcanicity , or volcanic activity

525-490: A chemical bond. This effect can be used to separate isotopes by chemical means. The Szilard–Chalmers effect was discovered in 1934 by Leó Szilárd and Thomas A. Chalmers. They observed that after bombardment by neutrons, the breaking of a bond in liquid ethyl iodide allowed radioactive iodine to be removed. Radioactive primordial nuclides found in the Earth are residues from ancient supernova explosions that occurred before

630-493: A common feature at explosive volcanoes on Earth. Pyroclastic flows have been found on Venus, for example at the Dione Regio volcanoes. A phreatic eruption can occur when hot water under pressure is depressurised. Depressurisation reduces the boiling point of the water, so when depressurised the water suddenly boils. Or it may happen when groundwater is suddenly heated, flashing to steam suddenly. When water turns into steam in

735-551: A final section, is bound state beta decay of rhenium-187 . In this process, the beta electron-decay of the parent nuclide is not accompanied by beta electron emission, because the beta particle has been captured into the K-shell of the emitting atom. An antineutrino is emitted, as in all negative beta decays. If energy circumstances are favorable, a given radionuclide may undergo many competing types of decay, with some atoms decaying by one route, and others decaying by another. An example

840-422: A given total number of nucleons . This consequently produces a more stable (lower energy) nucleus. A hypothetical process of positron capture, analogous to electron capture, is theoretically possible in antimatter atoms, but has not been observed, as complex antimatter atoms beyond antihelium are not experimentally available. Such a decay would require antimatter atoms at least as complex as beryllium-7 , which

945-467: A ground energy state, also produce later internal conversion and gamma decay in almost 0.5% of the time. The daughter nuclide of a decay event may also be unstable (radioactive). In this case, it too will decay, producing radiation. The resulting second daughter nuclide may also be radioactive. This can lead to a sequence of several decay events called a decay chain (see this article for specific details of important natural decay chains). Eventually,

1050-425: A lava flow to cool rapidly. This splinters the surface of the lava, and the magma then collects into sacks that often pile up in front of the flow, forming a structure called a pillow. A’a lava has a rough, spiny surface made of clasts of lava called clinkers. Block lava is another type of lava, with less jagged fragments than in a’a lava. Pahoehoe lava is by far the most common lava type, both on Earth and probably

1155-409: A mechanical standpoint it is a water filled crevasse turned upside down. As magma rises into the vertical crack, the low density of the magma compared to the wall rock means that the pressure falls less rapidly than in the surrounding denser rock. If the average pressure of the magma and the surrounding rock are equal, the pressure in the dike exceeds that of the enclosing rock at the top of the dike, and

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1260-564: A million years), any traces of it have long since vanished. There are small traces of unstable isotopes in common minerals, and all the terrestrial planets , and the Moon, experience some of this heating. The icy bodies of the outer solar system experience much less of this heat because they tend to not be very dense and not have much silicate material (radioactive elements concentrate in silicates). On Neptune's moon Triton , and possibly on Mars, cryogeyser activity takes place. The source of heat

1365-537: A moon of Saturn . The ejecta may be composed of water, liquid nitrogen , ammonia , dust, or methane compounds. Cassini–Huygens also found evidence of a methane-spewing cryovolcano on the Saturnian moon Titan , which is believed to be a significant source of the methane found in its atmosphere. It is theorized that cryovolcanism may also be present on the Kuiper Belt Object Quaoar . A 2010 study of

1470-414: A neutrino and a gamma ray from the excited nucleus (and often also Auger electrons and characteristic X-rays , as a result of the re-ordering of electrons to fill the place of the missing captured electron). These types of decay involve the nuclear capture of electrons or emission of electrons or positrons, and thus acts to move a nucleus toward the ratio of neutrons to protons that has the least energy for

1575-436: A nuclear excited state , the decay is a nuclear transmutation resulting in a daughter containing a different number of protons or neutrons (or both). When the number of protons changes, an atom of a different chemical element is created. There are 28 naturally occurring chemical elements on Earth that are radioactive, consisting of 35 radionuclides (seven elements have two different radionuclides each) that date before

1680-455: A partially molten core. However, the Moon does have many volcanic features such as maria (the darker patches seen on the Moon), rilles and domes . The planet Venus has a surface that is 90% basalt , indicating that volcanism played a major role in shaping its surface. The planet may have had a major global resurfacing event about 500 million years ago, from what scientists can tell from

1785-480: A phreatic eruption, it expands at supersonic speeds, up to 1,700 times its original volume. This can be enough to shatter solid rock, and hurl rock fragments hundreds of metres. A phreatomagmatic eruption occurs when hot magma makes contact with water, creating an explosion. One mechanism for explosive cryovolcanism is cryomagma making contact with clathrate hydrates . Clathrate hydrates, if exposed to warm temperatures, readily decompose. A 1982 article pointed out

1890-447: A radioactive nuclide with a half-life of only 5700(30) years, is constantly produced in Earth's upper atmosphere due to interactions between cosmic rays and nitrogen. Nuclides that are produced by radioactive decay are called radiogenic nuclides , whether they themselves are stable or not. There exist stable radiogenic nuclides that were formed from short-lived extinct radionuclides in

1995-403: A reduction of summed rest mass , once the released energy (the disintegration energy ) has escaped in some way. Although decay energy is sometimes defined as associated with the difference between the mass of the parent nuclide products and the mass of the decay products, this is true only of rest mass measurements, where some energy has been removed from the product system. This is true because

2100-494: A rigid open channel, in the lithosphere and settles at the level of hydrostatic equilibrium . Despite how it explains observations well (which newer models cannot), such as an apparent concordance of the elevation of volcanoes near each other, it cannot be correct and is now discredited, because the lithosphere thickness derived from it is too large for the assumption of a rigid open channel to hold. Unlike silicate volcanism, where melt can rise by its own buoyancy until it reaches

2205-528: A stable nuclide is produced. Any decay daughters that are the result of an alpha decay will also result in helium atoms being created. Some radionuclides may have several different paths of decay. For example, 35.94(6) % of bismuth-212 decays, through alpha-emission, to thallium-208 while 64.06(6) % of bismuth-212 decays, through beta-emission, to polonium-212 . Both thallium-208 and polonium-212 are radioactive daughter products of bismuth-212, and both decay directly to stable lead-208 . According to

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2310-399: A third-life, or even a (1/√2)-life, could be used in exactly the same way as half-life; but the mean life and half-life t 1/2 have been adopted as standard times associated with exponential decay. Those parameters can be related to the following time-dependent parameters: These are related as follows: where N 0 is the initial amount of active substance — substance that has

2415-446: A uniform subsurface ocean, may instead take place from discrete liquid reservoirs. The first way these can form is a plume of warm ice welling up and then sinking back down, forming a convection current. A model developed to investigate the effects of this on Europa found that energy from tidal heating became focused in these plumes, allowing melting to occur in these shallow depths as the plume spreads laterally (horizontally). The next

2520-529: Is copper-64 , which has 29 protons, and 35 neutrons, which decays with a half-life of 12.7004(13) hours. This isotope has one unpaired proton and one unpaired neutron, so either the proton or the neutron can decay to the other particle, which has opposite isospin . This particular nuclide (though not all nuclides in this situation) is more likely to decay through beta plus decay ( 61.52(26) % ) than through electron capture ( 38.48(26) % ). The excited energy states resulting from these decays which fail to end in

2625-497: Is internal conversion , which results in an initial electron emission, and then often further characteristic X-rays and Auger electrons emissions, although the internal conversion process involves neither beta nor gamma decay. A neutrino is not emitted, and none of the electron(s) and photon(s) emitted originate in the nucleus, even though the energy to emit all of them does originate there. Internal conversion decay, like isomeric transition gamma decay and neutron emission, involves

2730-592: Is a switch from vertical to horizontal propagation of a fluid filled crack. Another mechanism is heating of ice from release of stress through lateral motion of fractures in the ice shell penetrating it from the surface, and even heating from large impacts can create such reservoirs. When material of a planetary body begins to melt, the melting first occurs in small pockets in certain high energy locations, for example grain boundary intersections and where different crystals react to form eutectic liquid , that initially remain isolated from one another, trapped inside rock. If

2835-423: Is also a valuable tool in estimating the absolute ages of certain materials. For geological materials, the radioisotopes and some of their decay products become trapped when a rock solidifies, and can then later be used (subject to many well-known qualifications) to estimate the date of the solidification. These include checking the results of several simultaneous processes and their products against each other, within

2940-450: Is considered radioactive . Three of the most common types of decay are alpha , beta , and gamma decay . The weak force is the mechanism that is responsible for beta decay, while the other two are governed by the electromagnetic and nuclear forces . Radioactive decay is a random process at the level of single atoms. According to quantum theory , it is impossible to predict when a particular atom will decay, regardless of how long

3045-447: Is driven by exsolution of volatiles that were previously dissolved into the cryomagma, similar to what happens in explosive silicate volcanism as seen on Earth, which is what is mainly covered below. Silica-rich magmas cool beneath the surface before they erupt. As they do this, bubbles exsolve from the magma. As the magma nears the surface, the bubbles and thus the magma increase in volume. The resulting pressure eventually breaks through

3150-598: Is entirely in the form of water, which freezes into ice on the frigid surface. This process is known as cryovolcanism , and is apparently most common on the moons of the outer planets of the Solar System . In 1989, the Voyager 2 spacecraft observed cryovolcanoes (ice volcanoes) on Triton , a moon of Neptune , and in 2005 the Cassini–Huygens probe photographed fountains of frozen particles erupting from Enceladus ,

3255-462: Is external (heat from the Sun) rather than internal. Decompression melting happens when solid material from deep beneath the body rises upwards. Pressure decreases as the material rises upwards, and so does the melting point. So, a rock that is solid at a given pressure and temperature can become liquid if the pressure, and thus melting point, decreases even if the temperature stays constant. However, in

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3360-477: Is formed when fluids and gases under pressure erupt to the surface, bringing mud with them. This pressure can be caused by the weight of overlying sediments over the fluid which pushes down on the fluid, preventing it from escaping, by fluid being trapped in the sediment, migrating from deeper sediment into other sediment or being made from chemical reactions in the sediment. They often erupt quietly, but sometimes they erupt flammable gases like methane. Cryovolcanism

3465-503: Is much more than the ambient pressure. Not only that, but any volatiles in the water will exsolve. The combination of these processes will release droplets and vapor, which can rise up the fracture, creating a plume. This is thought to be partially responsible for Enceladus's ice plumes. On Earth, volcanoes are most often found where tectonic plates are diverging or converging , and because most of Earth's plate boundaries are underwater, most volcanoes are found underwater. For example,

3570-487: Is partially due to the fact that melted material tends to be more mobile and less dense than the materials from which they were produced, which can cause it to rise to the surface. There are multiple ways to generate the heat needed for volcanism. Volcanism on outer solar system moons is powered mainly by tidal heating . Tidal heating caused by the deformation of a body's shape due to mutual gravitational attraction, which generates heat. Earth experiences tidal heating from

3675-460: Is pressurised in the same way. For a crack in the ice shell to propagate upwards, the fluid in it must have positive buoyancy or external stresses must be strong enough to break through the ice. External stresses could include those from tides or from overpressure due to freezing as explained above. There is yet another possible mechanism for ascent of cryovolcanic melts. If a fracture with water in it reaches an ocean or subsurface fluid reservoir,

3780-461: Is the eruption of volatiles into an environment below their freezing point. The processes behind it are different to silicate volcanism because the cryomagma (which is usually water-based) is normally denser than its surroundings, meaning it cannot rise by its own buoyancy. Sulfur lavas have a different behaviour to silicate ones. First, sulfur has a low melting point of about 120 degrees Celsius. Also, after cooling down to about 175 degrees Celsius

3885-418: Is the lightest known isotope of normal matter to undergo decay by electron capture. Shortly after the discovery of the neutron in 1932, Enrico Fermi realized that certain rare beta-decay reactions immediately yield neutrons as an additional decay particle, so called beta-delayed neutron emission . Neutron emission usually happens from nuclei that are in an excited state, such as the excited O* produced from

3990-461: Is the phenomenon where solids, liquids, gases, and their mixtures erupt to the surface of a solid-surface astronomical body such as a planet or a moon. It is caused by the presence of a heat source, usually internally generated, inside the body; the heat is generated by various processes, such as radioactive decay or tidal heating . This heat partially melts solid material in the body or turns material into gas. The mobilized material rises through

4095-574: The Big Bang theory , stable isotopes of the lightest three elements ( H , He, and traces of Li ) were produced very shortly after the emergence of the universe, in a process called Big Bang nucleosynthesis . These lightest stable nuclides (including deuterium ) survive to today, but any radioactive isotopes of the light elements produced in the Big Bang (such as tritium ) have long since decayed. Isotopes of elements heavier than boron were not produced at all in

4200-457: The Moon , deforming by up to 1 metre (3 feet), but this does not make up a major portion of Earth's total heat . During a planet's formation , it would have experienced heating from impacts from planetesimals , which would have dwarfed even the asteroid impact that caused the extinction of dinosaurs . This heating could trigger differentiation , further heating the planet. The larger a body is,

4305-684: The U.S. National Cancer Institute (NCI), International Agency for Research on Cancer (IARC) and the Radiation Effects Research Foundation of Hiroshima ) studied definitively through meta-analysis the damage resulting from the "low doses" that have afflicted survivors of the atomic bombings of Hiroshima and Nagasaki and also in numerous accidents at nuclear plants that have occurred. These scientists reported, in JNCI Monographs: Epidemiological Studies of Low Dose Ionizing Radiation and Cancer Risk , that

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4410-436: The contact angle of the melted material allows the melt to wet crystal faces and run along grain boundaries , the melted material will accumulate into larger quantities. On the other hand, if the angle is greater than about 60 degrees, much more melt must form before it can separate from its parental rock. Studies of rocks on Earth suggest that melt in hot rocks quickly collects into pockets and veins that are much larger than

4515-578: The core–mantle boundary , 3,000 kilometers (1,900 mi) deep within Earth. This results in hotspot volcanism , of which the Hawaiian hotspot is an example. Volcanoes are usually not created where two tectonic plates slide past one another. In 1912–1952, in the Northern Hemisphere, studies show that within this time, winters were warmer due to no massive eruptions that had taken place. These studies demonstrate how these eruptions can cause changes within

4620-514: The exoplanet COROT-7b , which was detected by transit in 2009, suggested that tidal heating from the host star very close to the planet and neighboring planets could generate intense volcanic activity similar to that found on Io. Radioactivity Radioactive decay (also known as nuclear decay , radioactivity , radioactive disintegration , or nuclear disintegration ) is the process by which an unstable atomic nucleus loses energy by radiation . A material containing unstable nuclei

4725-405: The grain size, in contrast to the model of rigid melt percolation . Melt, instead of uniformly flowing out of source rock, flows out through rivulets which join to create larger veins. Under the influence of buoyancy , the melt rises. Diapirs may also form in non-silicate bodies, playing a similar role in moving warm material towards the surface. A dike is a vertical fluid-filled crack, from

4830-600: The röntgen unit, and the International X-ray and Radium Protection Committee (IXRPC) was formed. Rolf Sievert was named chairman, but a driving force was George Kaye of the British National Physical Laboratory . The committee met in 1931, 1934, and 1937. After World War II , the increased range and quantity of radioactive substances being handled as a result of military and civil nuclear programs led to large groups of occupational workers and

4935-483: The 1930s, after a number of cases of bone necrosis and death of radium treatment enthusiasts, radium-containing medicinal products had been largely removed from the market ( radioactive quackery ). Only a year after Röntgen 's discovery of X-rays, the American engineer Wolfram Fuchs (1896) gave what is probably the first protection advice, but it was not until 1925 that the first International Congress of Radiology (ICR)

5040-408: The Big Bang, and these first five elements do not have any long-lived radioisotopes. Thus, all radioactive nuclei are, therefore, relatively young with respect to the birth of the universe, having formed later in various other types of nucleosynthesis in stars (in particular, supernovae ), and also during ongoing interactions between stable isotopes and energetic particles. For example, carbon-14 ,

5145-560: The Big Dan Shear Zone also displaced felsic dikes north of the shear zone . However, considerable displacement of the dikes at this location is unknown. The most recent tectonic activity of the Big Dan Shear Zone displaced a Proterozoic dike composed of diabase , which intersects the zone. A similar abundance of felsic dikes are adjacent to Arsenic Lake just west of Highway 11 , indicating that similar tectonism also occurred along that structural zone. Therefore, these north-trending shear zones may have been tectonically active for at least

5250-402: The Earth's atmosphere or crust . The decay of the radionuclides in rocks of the Earth's mantle and crust contribute significantly to Earth's internal heat budget . While the underlying process of radioactive decay is subatomic, historically and in most practical cases it is encountered in bulk materials with very large numbers of atoms. This section discusses models that connect events at

5355-460: The Earth's atmosphere. Large eruptions can affect atmospheric temperature as ash and droplets of sulfuric acid obscure the Sun and cool Earth's troposphere . Historically, large volcanic eruptions have been followed by volcanic winters which have caused catastrophic famines. Earth's Moon has no large volcanoes and no current volcanic activity, although recent evidence suggests it may still possess

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5460-554: The European Mars Express spacecraft has found evidence that volcanic activity may have occurred on Mars in the recent past as well. Jupiter 's moon Io is the most volcanically active object in the Solar System because of tidal interaction with Jupiter. It is covered with volcanoes that erupt sulfur , sulfur dioxide and silicate rock, and as a result, Io is constantly being resurfaced. There are only two planets in

5565-563: The United States Nuclear Regulatory Commission permits the use of the unit curie alongside SI units, the European Union European units of measurement directives required that its use for "public health ... purposes" be phased out by 31 December 1985. The effects of ionizing radiation are often measured in units of gray for mechanical or sievert for damage to tissue. Radioactive decay results in

5670-486: The atom has existed. However, for a significant number of identical atoms, the overall decay rate can be expressed as a decay constant or as a half-life . The half-lives of radioactive atoms have a huge range: from nearly instantaneous to far longer than the age of the universe . The decaying nucleus is called the parent radionuclide (or parent radioisotope ), and the process produces at least one daughter nuclide . Except for gamma decay or internal conversion from

5775-408: The atomic level to observations in aggregate. The decay rate , or activity , of a radioactive substance is characterized by the following time-independent parameters: Although these are constants, they are associated with the statistical behavior of populations of atoms. In consequence, predictions using these constants are less accurate for minuscule samples of atoms. In principle a half-life,

5880-664: The beta decay of N. The neutron emission process itself is controlled by the nuclear force and therefore is extremely fast, sometimes referred to as "nearly instantaneous". Isolated proton emission was eventually observed in some elements. It was also found that some heavy elements may undergo spontaneous fission into products that vary in composition. In a phenomenon called cluster decay , specific combinations of neutrons and protons other than alpha particles (helium nuclei) were found to be spontaneously emitted from atoms. Other types of radioactive decay were found to emit previously seen particles but via different mechanisms. An example

5985-506: The biological effects of radiation due to radioactive substances were less easy to gauge. This gave the opportunity for many physicians and corporations to market radioactive substances as patent medicines . Examples were radium enema treatments, and radium-containing waters to be drunk as tonics. Marie Curie protested against this sort of treatment, warning that "radium is dangerous in untrained hands". Curie later died from aplastic anaemia , likely caused by exposure to ionizing radiation. By

6090-437: The body's interior and may break through the solid surface. For volcanism to occur, the temperature of the mantle must have risen to about half its melting point. At this point, the mantle's viscosity will have dropped to about 10 Pascal-seconds . When large scale melting occurs, the viscosity rapidly falls to 10 Pascal-seconds or even less, increasing the heat transport rate a million-fold. The occurrence of volcanism

6195-457: The carbon-14 in individual tree rings, for example). The Szilard–Chalmers effect is the breaking of a chemical bond as a result of a kinetic energy imparted from radioactive decay. It operates by the absorption of neutrons by an atom and subsequent emission of gamma rays, often with significant amounts of kinetic energy. This kinetic energy, by Newton's third law , pushes back on the decaying atom, which causes it to move with enough speed to break

6300-455: The case of water, increasing pressure decreases melting point until a pressure of 0.208 GPa is reached, after which the melting point increases with pressure. Flux melting occurs when the melting point is lowered by the addition of volatiles, for example, water or carbon dioxide. Like decompression melting, it is not caused by an increase in temperature, but rather by a decrease in melting point. Cryovolcanism , instead of originating in

6405-416: The cryomagma less dense), or with the presence of a densifying agent in the ice shell. Another is to pressurise the fluid to overcome negative buoyancy and make it reach the surface. When the ice shell above a subsurface ocean thickens, it can pressurise the entire ocean (in cryovolcanism, frozen water or brine is less dense than in liquid form). When a reservoir of liquid partially freezes, the remaining liquid

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6510-467: The dangers involved in the careless use of X-rays were not being heeded, either by industry or by his colleagues. By this time, Rollins had proved that X-rays could kill experimental animals, could cause a pregnant guinea pig to abort, and that they could kill a foetus. He also stressed that "animals vary in susceptibility to the external action of X-light" and warned that these differences be considered when patients were treated by means of X-rays. However,

6615-441: The dark after exposure to light, and Becquerel suspected that the glow produced in cathode-ray tubes by X-rays might be associated with phosphorescence. He wrapped a photographic plate in black paper and placed various phosphorescent salts on it. All results were negative until he used uranium salts. The uranium salts caused a blackening of the plate in spite of the plate being wrapped in black paper. These radiations were given

6720-409: The decay energy is transformed to thermal energy, which retains its mass. Decay energy, therefore, remains associated with a certain measure of the mass of the decay system, called invariant mass , which does not change during the decay, even though the energy of decay is distributed among decay particles. The energy of photons, the kinetic energy of emitted particles, and, later, the thermal energy of

6825-424: The decay energy must always carry mass with it, wherever it appears (see mass in special relativity ) according to the formula E  =  mc . The decay energy is initially released as the energy of emitted photons plus the kinetic energy of massive emitted particles (that is, particles that have rest mass). If these particles come to thermal equilibrium with their surroundings and photons are absorbed, then

6930-538: The density of impact craters on the surface. Lava flows are widespread and forms of volcanism not present on Earth occur as well. Changes in the planet's atmosphere and observations of lightning have been attributed to ongoing volcanic eruptions, although there is no confirmation of whether or not Venus is still volcanically active. However, radar sounding by the Magellan probe revealed evidence for comparatively recent volcanic activity at Venus's highest volcano Maat Mons , in

7035-532: The difference in height between the basin and the height of the surrounding terrain could allow eruption of magma which otherwise would have stayed beneath the surface. A 2011 article showed that there would be zones of enhanced magma ascent at the margins of an impact basin. Not all of these mechanisms, and maybe even none, operate on a given body . Silicate volcanism occurs where silicate materials are erupted. Silicate lava flows, like those found on Earth, solidify at about 1000 degrees Celsius. A mud volcano

7140-423: The discovery of the positron in cosmic ray products, it was realized that the same process that operates in classical beta decay can also produce positrons ( positron emission ), along with neutrinos (classical beta decay produces antineutrinos). In electron capture, some proton-rich nuclides were found to capture their own atomic electrons instead of emitting positrons, and subsequently, these nuclides emit only

7245-428: The early Solar System. The extra presence of these stable radiogenic nuclides (such as xenon-129 from extinct iodine-129 ) against the background of primordial stable nuclides can be inferred by various means. Radioactive decay has been put to use in the technique of radioisotopic labeling , which is used to track the passage of a chemical substance through a complex system (such as a living organism ). A sample of

7350-433: The enrichment of magma at the top of a dike by gas which is released when the dike breaches the surface, followed by magma from lower down than did not get enriched with gas. The reason the dissolved gas in the magma separates from it when the magma nears the surface is due to the effects of temperature and pressure on gas solubility . Pressure increases gas solubility, and if a liquid with dissolved gas in it depressurises,

7455-528: The first to realize that many decay processes resulted in the transmutation of one element to another. Subsequently, the radioactive displacement law of Fajans and Soddy was formulated to describe the products of alpha and beta decay . The early researchers also discovered that many other chemical elements , besides uranium, have radioactive isotopes. A systematic search for the total radioactivity in uranium ores also guided Pierre and Marie Curie to isolate two new elements: polonium and radium . Except for

7560-427: The form of ash flows near the summit and on the northern flank. However, the interpretation of the flows as ash flows has been questioned. There are several extinct volcanoes on Mars , four of which are vast shield volcanoes far bigger than any on Earth. They include Arsia Mons , Ascraeus Mons , Hecates Tholus , Olympus Mons , and Pavonis Mons . These volcanoes have been extinct for many millions of years, but

7665-515: The formation of the Solar System . They are the fraction of radionuclides that survived from that time, through the formation of the primordial solar nebula , through planet accretion , and up to the present time. The naturally occurring short-lived radiogenic radionuclides found in today's rocks , are the daughters of those radioactive primordial nuclides. Another minor source of naturally occurring radioactive nuclides are cosmogenic nuclides , that are formed by cosmic ray bombardment of material in

7770-605: The gas in the ash as it expands chills the magma fragments, often forming tiny glass shards recognisable as portions of the walls of former liquid bubbles. In more fluid magmas the bubble walls may have time to reform into spherical liquid droplets. The final state of the colloids depends strongly on the ratio of liquid to gas. Gas-poor magmas end up cooling into rocks with small cavities, becoming vesicular lava . Gas-rich magmas cool to form rocks with cavities that nearly touch, with an average density less than that of water, forming pumice . Meanwhile, other material can be accelerated with

7875-432: The gas will tend to exsolve (or separate) from the liquid. An example of this is what happens when a bottle of carbonated drink is quickly opened: when the seal is opened, pressure decreases and bubbles of carbon dioxide gas appear throughout the liquid. Fluid magmas erupt quietly. Any gas that has exsolved from the magma easily escapes even before it reaches the surface. However, in viscous magmas, gases remain trapped in

7980-462: The gas, becoming volcanic bombs . These can travel with so much energy that large ones can create craters when they hit the ground. A colloid of volcanic gas and magma can form as a density current called a pyroclastic flow . This occurs when erupted material falls back to the surface. The colloid is somewhat fluidised by the gas, allowing it to spread. Pyroclastic flows can often climb over obstacles, and devastate human life. Pyroclastic flows are

8085-433: The lava rapidly loses viscosity, unlike silicate lavas like those found on Earth. When magma erupts onto a planet's surface, it is termed lava . Viscous lavas form short, stubby glass-rich flows. These usually have a wavy solidified surface texture. More fluid lavas have solidified surface textures that volcanologists classify into four types. Pillow lava forms when a trigger, often lava making contact with water, causes

8190-418: The limit of measurement) to radioactive decay. Radioactive decay is seen in all isotopes of all elements of atomic number 83 ( bismuth ) or greater. Bismuth-209 , however, is only very slightly radioactive, with a half-life greater than the age of the universe; radioisotopes with extremely long half-lives are considered effectively stable for practical purposes. In analyzing the nature of the decay products, it

8295-426: The magma even after they have exsolved, forming bubbles inside the magma. These bubbles enlarge as the magma nears the surface due to the dropping pressure, and the magma grows substantially. This fact gives volcanoes erupting such material a tendency to ‘explode’, although instead of the pressure increase associated with an explosion, pressure always decreases in a volcanic eruption. Generally, explosive cryovolcanism

8400-429: The name "Becquerel Rays". It soon became clear that the blackening of the plate had nothing to do with phosphorescence, as the blackening was also produced by non-phosphorescent salts of uranium and by metallic uranium. It became clear from these experiments that there was a form of invisible radiation that could pass through paper and was causing the plate to react as if exposed to light. At first, it seemed as though

8505-411: The names alpha , beta , and gamma, in increasing order of their ability to penetrate matter. Alpha decay is observed only in heavier elements of atomic number 52 ( tellurium ) and greater, with the exception of beryllium-8 (which decays to two alpha particles). The other two types of decay are observed in all the elements. Lead, atomic number 82, is the heaviest element to have any isotopes stable (to

8610-437: The new epidemiological studies directly support excess cancer risks from low-dose ionizing radiation. In 2021, Italian researcher Sebastiano Venturi reported the first correlations between radio-caesium and pancreatic cancer with the role of caesium in biology, in pancreatitis and in diabetes of pancreatic origin. The International System of Units (SI) unit of radioactive activity is the becquerel (Bq), named in honor of

8715-431: The new radiation was similar to the then recently discovered X-rays. Further research by Becquerel, Ernest Rutherford , Paul Villard , Pierre Curie , Marie Curie , and others showed that this form of radioactivity was significantly more complicated. Rutherford was the first to realize that all such elements decay in accordance with the same mathematical exponential formula. Rutherford and his student Frederick Soddy were

8820-672: The other terrestrial planets. It has a smooth surface, with mounds, hollows and folds. A volcanic eruption could just be a simple outpouring of material onto the surface of a planet, but they usually involve a complex mixture of solids, liquids and gases which behave in equally complex ways. Some types of explosive eruptions can release energy a quarter that of an equivalent mass of TNT . Volcanic eruptions on Earth have been consistently observed to progress from erupting gas rich material to gas depleted material, although an eruption may alternate between erupting gas rich to gas depleted material and vice versa multiple times. This can be explained by

8925-443: The possibility that the production of pressurised gas upon destabilisation of clathrate hydrates making contact with warm rising magma could produce an explosion that breaks through the surface, resulting in explosive cryovolcanism. If a fracture reaches the surface of an icy body and the column of rising water is exposed to the near-vacuum of the surface of most icy bodies, it will immediately start to boil, because its vapor pressure

9030-509: The pressure of the rock is greater than that of the dike at its bottom. So the magma thus pushes the crack upwards at its top, but the crack is squeezed closed at its bottom due to an elastic reaction (similar to the bulge next to a person sitting down on a springy sofa). Eventually, the tail gets so narrow it nearly pinches off, and no more new magma will rise into the crack. The crack continues to ascend as an independent pod of magma. This model of volcanic eruption posits that magma rises through

9135-678: The public being potentially exposed to harmful levels of ionising radiation. This was considered at the first post-war ICR convened in London in 1950, when the present International Commission on Radiological Protection (ICRP) was born. Since then the ICRP has developed the present international system of radiation protection, covering all aspects of radiation hazards. In 2020, Hauptmann and another 15 international researchers from eight nations (among them: Institutes of Biostatistics, Registry Research, Centers of Cancer Epidemiology, Radiation Epidemiology, and also

9240-435: The radioactivity of radium, the chemical similarity of radium to barium made these two elements difficult to distinguish. Marie and Pierre Curie's study of radioactivity is an important factor in science and medicine. After their research on Becquerel's rays led them to the discovery of both radium and polonium, they coined the term "radioactivity" to define the emission of ionizing radiation by some heavy elements. (Later

9345-446: The release of energy by an excited nuclide, without the transmutation of one element into another. Rare events that involve a combination of two beta-decay-type events happening simultaneously are known (see below). Any decay process that does not violate the conservation of energy or momentum laws (and perhaps other particle conservation laws) is permitted to happen, although not all have been detected. An interesting example discussed in

9450-530: The same sample. In a similar fashion, and also subject to qualification, the rate of formation of carbon-14 in various eras, the date of formation of organic matter within a certain period related to the isotope's half-life may be estimated, because the carbon-14 becomes trapped when the organic matter grows and incorporates the new carbon-14 from the air. Thereafter, the amount of carbon-14 in organic matter decreases according to decay processes that may also be independently cross-checked by other means (such as checking

9555-467: The scientist Henri Becquerel . One Bq is defined as one transformation (or decay or disintegration) per second. An older unit of radioactivity is the curie , Ci, which was originally defined as "the quantity or mass of radium emanation in equilibrium with one gram of radium (element)". Today, the curie is defined as 3.7 × 10 disintegrations per second, so that 1  curie (Ci) = 3.7 × 10  Bq . For radiological protection purposes, although

9660-417: The shallow crust, in cryovolcanism, the water (cryomagmas tend to be water based) is denser than the ice above it. One way to allow cryomagma to reach the surface is to make the water buoyant, by making the water less dense, either through the presence of other compounds that reverse negative buoyancy, or with the addition of exsolved gas bubbles in the cryomagma that were previously dissolved into it (that makes

9765-416: The slower it loses heat. In larger bodies, for example Earth, this heat, known as primordial heat, still makes up much of the body's internal heat, but the Moon, which is smaller than Earth, has lost most of this heat. Another heat source is radiogenic heat, caused by radioactive decay . The decay of aluminium-26 would have significantly heated planetary embryos, but due to its short half-life (less than

9870-442: The solar system where volcanoes can be easily seen due to their high activity, Earth and Io. Its lavas are the hottest known anywhere in the Solar System, with temperatures exceeding 1,800 K (1,500 °C). In February 2001, the largest recorded volcanic eruptions in the Solar System occurred on Io. Europa , the smallest of Jupiter's Galilean moons , also appears to have an active volcanic system, except that its volcanic activity

9975-429: The substance is synthesized with a high concentration of unstable atoms. The presence of the substance in one or another part of the system is determined by detecting the locations of decay events. On the premise that radioactive decay is truly random (rather than merely chaotic ), it has been used in hardware random-number generators . Because the process is not thought to vary significantly in mechanism over time, it

10080-415: The surface, and the release of pressure causes more gas to exsolve, doing so explosively. The gas may expand at hundreds of metres per second, expanding upward and outward. As the eruption progresses, a chain reaction causes the magma to be ejected at higher and higher speeds. The violently expanding gas disperses and breaks up magma, forming a colloid of gas and magma called volcanic ash . The cooling of

10185-541: The surrounding matter, all contribute to the invariant mass of the system. Thus, while the sum of the rest masses of the particles is not conserved in radioactive decay, the system mass and system invariant mass (and also the system total energy) is conserved throughout any decay process. This is a restatement of the equivalent laws of conservation of energy and conservation of mass . Early researchers found that an electric or magnetic field could split radioactive emissions into three types of beams. The rays were given

10290-927: The term was generalized to all elements.) Their research on the penetrating rays in uranium and the discovery of radium launched an era of using radium for the treatment of cancer. Their exploration of radium could be seen as the first peaceful use of nuclear energy and the start of modern nuclear medicine . The dangers of ionizing radiation due to radioactivity and X-rays were not immediately recognized. The discovery of X‑rays by Wilhelm Röntgen in 1895 led to widespread experimentation by scientists, physicians, and inventors. Many people began recounting stories of burns, hair loss and worse in technical journals as early as 1896. In February of that year, Professor Daniel and Dr. Dudley of Vanderbilt University performed an experiment involving X-raying Dudley's head that resulted in his hair loss. A report by Dr. H.D. Hawks, of his suffering severe hand and chest burns in an X-ray demonstration,

10395-492: The time of formation of the Solar System . These 35 are known as primordial radionuclides . Well-known examples are uranium and thorium , but also included are naturally occurring long-lived radioisotopes, such as potassium-40 . Each of the heavy primordial radionuclides participates in one of the four decay chains . Radioactivity was discovered in 1896 by scientists Henri Becquerel and Marie Curie , while working with phosphorescent materials. These materials glow in

10500-439: The water to exsolve into gas. The elastic nature of the ice shell would likely prevent the fracture reaching the surface, and the crack would instead pinch off, enclosing the gas and liquid. The gas would increase buoyancy and could allow the crack to reach the surface. Even impacts can create conditions that allow for enhanced ascent of magma. An impact may remove the top few kilometres of crust, and pressure differences caused by

10605-459: The water would rise to its level of hydrostatic equilibrium, at about nine-tenths of the way to the surface. Tides which induce compression and tension in the ice shell may pump the water farther up. A 1988 article proposed a possibility for fractures propagating upwards from the subsurface ocean of Jupiter's moon Europa. It proposed that a fracture propagating upwards would possess a low pressure zone at its tip, allowing volatiles dissolved within

10710-515: Was almost always found to be associated with other types of decay, and occurred at about the same time, or afterwards. Gamma decay as a separate phenomenon, with its own half-life (now termed isomeric transition ), was found in natural radioactivity to be a result of the gamma decay of excited metastable nuclear isomers , which were in turn created from other types of decay. Although alpha, beta, and gamma radiations were most commonly found, other types of emission were eventually discovered. Shortly after

10815-570: Was held and considered establishing international protection standards. The effects of radiation on genes, including the effect of cancer risk, were recognized much later. In 1927, Hermann Joseph Muller published research showing genetic effects and, in 1946, was awarded the Nobel Prize in Physiology or Medicine for his findings. The second ICR was held in Stockholm in 1928 and proposed the adoption of

10920-442: Was obvious from the direction of the electromagnetic forces applied to the radiations by external magnetic and electric fields that alpha particles carried a positive charge, beta particles carried a negative charge, and gamma rays were neutral. From the magnitude of deflection, it was clear that alpha particles were much more massive than beta particles . Passing alpha particles through a very thin glass window and trapping them in

11025-683: Was the first of many other reports in Electrical Review . Other experimenters, including Elihu Thomson and Nikola Tesla , also reported burns. Thomson deliberately exposed a finger to an X-ray tube over a period of time and suffered pain, swelling, and blistering. Other effects, including ultraviolet rays and ozone, were sometimes blamed for the damage, and many physicians still claimed that there were no effects from X-ray exposure at all. Despite this, there were some early systematic hazard investigations, and as early as 1902 William Herbert Rollins wrote almost despairingly that his warnings about

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