User:Marshallsumter/Radiation astronomy2/Volcanoes

Def. a "burst, split, or break" is called a rupture.

Def. an "opening through which gases, especially air, can pass" is called a vent.

Def. "a [long, narrow] crack or opening [made by breaking or splitting, especially] in a rock [or earth] " is called a fissure.

Def. "melted rock ejected by a volcano from its crater or fissured sides" is called a lava.

Def. a "[vent or fissure on the surface of a planet (usually in a mountainous form) with] a magma chamber attached to the mantle of the [a] planet or moon, periodically erupts [erupting] forth lava and volcanic gases [onto the surface] " is called a volcano.

Muons
"The muons inherit the high energy of the parent cosmic rays, which enables them to penetrate and pass through the rock of the volcano and to be detected on the other side of the mountain. Because denser materials absorb more muons (just as dense materials such as bone absorb more X-rays), this provides a basis for producing shadow images of the volcano’s interior."

"Muon radiography was first used in 1971 – not for volcanoes, but for investigating the interior of the pyramid of Chefren at Giza, Egypt. The Nobel-prize winning physicist Louis Alvarez placed a muon detector inside the pyramid to pick up changes in muon flux (rate of muon flow) that could indicate the presence of a hidden burial chamber. However, none was found."

"In 2007, Hiroyuki Tanaka and collaborators from the University of Tokyo were the first to apply this technique to volcanoes. They carried out radiography of the top part of the Asama volcano in Honshu, Japan, which revealed a region with rock of low density under the bottom of the crater. The presence of low-density regions can be used in computer simulations that predict how possible eruptions could develop, indicating the most dangerous areas around the volcano. Their observations showed that muon radiography could indeed produce useful images of the internal structure of volcanoes."

"The really important advantages of muon radiography of volcanoes are two-fold. First, whereas current indirect methods can provide information to a spatial resolution of some 100 m, muon radiography can be up to ten times more specific, mapping internal structures to a resolution of some 10 m. Second, muon radiography offers the possibility of continuous monitoring, thus potentially revealing the evolution of structures over time. The time resolution depends on the thickness of the rock traversed by the muons: the thicker it is, the fainter the muon flux and the longer it takes to accumulate enough muons for a picture. The time needed can thus be weeks, months or years."

Vesuvius "is a special challenge, not only because it represents the highest volcanic risk in Europe, but also because of the mountain’s unusual structure. Vesuvius is in fact situated within the remnants of a much larger volcano, Mount Somma. Moreover, inside the summit of Vesuvius is a crater that is 500 m wide and 300 m deep: this means that, to look below the bottom of the crater, muons have to penetrate deep into the mountain, through almost two kilometres of rock, to reach the detector on the opposite side of the volcano. Only muons of very high energy travelling in a near-horizontal direction are able to pass through all this rock, so their flux at the detector is very low, making imaging extremely difficult."

Radars
"The recently active volcano Mt. Manaro is the dominant feature in this shaded relief image [on the right] of Ambae Island, part of the Vanuatu archipelago located 1400 miles northeast of Sydney, Australia. About 5000 inhabitants, half the island's population, were evacuated in early December from the path of a possible lahar, or mud flow, when the volcano started spewing clouds of steam and toxic gases 10,000 feet into the atmosphere."

"Last active in 1996, the 1496 meter (4908 ft.) high Hawaiian-style basaltic shield volcano features two lakes within its summit caldera, or crater. The ash and gas plume is actually emerging from a vent at the center of Lake Voui (at left), which was formed approximately 425 years ago after an explosive eruption."

"Two visualization methods were combined to produce the image: shading and color coding of topographic height. The shade image was derived by computing topographic slope in the northwest-southeast direction, so that northwest slopes appear bright and southeast slopes appear dark. Color coding is directly related to topographic height, with green at the lower elevations, rising through yellow and tan, to white at the highest elevations."

"Elevation data used in this image were acquired by the Shuttle Radar Topography Mission [SRTM] aboard the Space Shuttle Endeavour, launched on Feb. 11, 2000. SRTM used the same radar instrument that comprised the Spaceborne Imaging Radar-C/X-Band Synthetic Aperture Radar (SIR-C/X-SAR) that flew twice on the Space Shuttle Endeavour in 1994. SRTM was designed to collect 3-D measurements of the Earth's surface. To collect the 3-D data, engineers added a 60-meter (approximately 200-foot) mast, installed additional C-band and X-band antennas, and improved tracking and navigation devices."

"Location: 15.4 degree south latitude, 167.9 degrees east longitude; Orientation: North toward the top, Mercator projection; Size: 36.8 by 27.8 kilometers (22.9 by 17.3 miles); Image Data [is a] shaded and colored SRTM elevation model"

On the left is a space radar image of Klyuchevskaya sopka.

"This is an image of the area of the Kliuchevskoi volcano, Kamchatka, Russia, which began to erupt on September 30, 1994. Kliuchevskoi is the blue triangular peak in the center of the image, towards the left edge of the bright red area that delineates bare snow cover. The image was acquired by the Spaceborne Imaging Radar-C/X-Band Synthetic Aperture Radar (SIR-C/X-SAR) aboard the space shuttle Endeavour on its 88th orbit on October 5, 1994. The image shows an area approximately 75 kilometers by 100 kilometers (46 miles by 62 miles) that is centered at 56.07 degrees north latitude and 160.84 degrees east longitude. North is toward the bottom of the image. The radar illumination is from the top of the image. The Kamchatka volcanoes are among the most active volcanoes in the world. The volcanic zone sits above a tectonic plate boundary, where the Pacific plate is sinking beneath the northeast edge of the Eurasian plate. The Endeavour crew obtained dramatic video and photographic images of this region during the eruption [...]. The colors in this image were obtained using the following radar channels: red represents the L-band, HH (horizontally transmitted and received) channel; green represents the L-band, HV (horizontally transmitted and vertically received) channel; blue represents the C-band, HV (horizontally transmitted and vertically received) channel. In addition to Kliuchevskoi, two other active volcanoes are visible in the image. Bezymianny, the circular crater above and to the right of Kliuchevskoi, contains a slowly growing lava dome. Tolbachik is the large volcano with a dark summit crater near the upper right edge of the red snow covered area. The Kamchatka River runs from right to left across the bottom of the image. The 1994 eruption of Kliuchevskoi included massive ejections of gas, vapor and ash, which reached altitudes of 15,000 meters (50,000 feet). Melting snow mixed with volcanic ash triggered mud flows on the flanks of the volcano. Paths of these flows can be seen as thin lines in various shades of blue and green on the north flank in the center of the image."

Ashfalls
The mushroom-shaped plume rose from avalanches of hot debris that cascaded down the north flank of Mount Redoubt.

Bombs
Volcanic bombs are thrown into the sky and travel some distance before returning to the ground. Def. "distinctively shaped [natural] projectiles ... which acquired their shape essentially before landing" are called bombs.

Def. a bomb "ejected from a volcanic vent" is called a volcanic bomb.

Volcanic bombs can be thrown many kilometres from an erupting vent, and often acquire aerodynamic shapes during their flight.

The image at top right is an "[a]ccretionary lava ball [coming] to rest on the grass after rolling off the top of an ‘a‘a flow in Royal Gardens subdivision. Accretionary lava balls form as viscous lava is molded around a core of already solidified lava."

Volcanic bombs cool into solid fragments before they reach the ground. Because volcanic bombs cool after they leave the volcano, they do not have grains making them extrusive igneous rocks. Volcanic bombs can be thrown many kilometres from an erupting vent, and often acquire aerodynamic shapes during their flight.

Volcanic bombs can be extremely large; the 1935 eruption of Mount Asama in Japan expelled bombs measuring 5–6 m in diameter up to 600 m from the vent. A large volcanic bomb is shown in the third image at right from Strohn, Germany.

Volcanic bombs are known to occasionally explode from internal gas pressure as they cool, but explosions are rare. Bomb explosions are most often observed in 'bread-crust' type bombs.

Ribbon or cylindrical bombs form from highly to moderately fluid magma, ejected as irregular strings and blobs. The strings break up into small segments which fall to the ground intact and look like ribbons. Hence, the name "ribbon bombs". These bombs are circular or flattened in cross section, are fluted along their length, and have tabular vesicles.

Spherical bombs also form from high to moderately fluid magma. In the case of spherical bombs, surface tension plays a major role in pulling the ejecta into spheres.

Spindle, fusiform, or almond/rotational bombs are formed by the same processes as spherical bombs, though the major difference being the partial nature of the spherical shape. Spinning during flight leaves these bombs looking elongated or almond shaped; the spinning theory behind these bombs' development has also given them the name 'fusiform bombs'. Spindle bombs are characterised by longitudinal fluting, one side slightly smoother and broader than the other. This smooth side represents the underside of the bomb as it fell through the air.

Cow pie bombs are formed when highly fluid magma falls from moderate height; so the bombs do not solidify before impact (they are still liquid when they strike the ground). They consequently flatten or splash and form irregular roundish disks, which resemble cow-dung.

Bread-crust bombs are formed if the outside of the lava bombs solidifies during their flights. They may develop cracked outer surfaces as the interiors continue to expand.

Cored bombs are bombs that have rinds of lava enclosing a core of previously consolidated lava. The core consists of accessory fragments of an earlier eruption, accidental fragments of country rock or, in rare cases, bits of lava formed earlier during the same eruption.

Mars
The topographic map of Mars at right is from the Mars Global Surveyor laser altimeter North is at the top. Notable features include the Tharsis volcanoes in the west (including Olympus Mons), Valles Marineris to the east of Tharsis, and Hellas Basin in the southern hemisphere.

The geography of Mars, also known as areography, entails the delineation and characterization of regions on Mars. Martian geography is mainly focused on what is called physical geography on Earth; that is the distribution of physical features across Mars and their cartographic representations.

Io volcanoes
The image at right represents "[t]he Jovian magnetosphere [magnetic field lines in blue], including the Io flux tube [in green], Jovian aurorae, the sodium cloud [in yellow], and sulfur torus [in red]."

"Io may be considered to be a unipolar generator which develops an emf [electromotive force] of 7 x 105 volts across its radial diameter (as seen from a coordinate frame fixed to Jupiter)."

"This voltage difference is transmitted along the magnetic flux tube which passes through Io. ... The current [in the flux tube] must be carried by keV electrons which are electrostatically accelerated at Io and at the top of Jupiter's ionosphere."

"Io's high density (4.1 g cm-3) suggests a silicate composition. A reasonable guess for its electrical conductivity might be the conductivity of the Earth's upper mantle, 5 x 10-5 ohm-1 cm-1 (Bullard 1967)."

As "a conducting body [transverses] a magnetic field [it] produces an induced electric field. ... The Jupiter-Io system ... operates as a unipolar inductor" ... Such unipolar inductors may be driven by electrical power, develop hotspots, and the "source of heating [may be] sufficient to account for the observed X-ray luminosity".

"The electrical surroundings of Io provide another energy source which has been estimated to be comparable with that of the [gravitational] tides (7). A current of 5 x 106 A is ... shunted across flux tubes of the Jovian field by the presence of Io (7-9)."

"[W]hen the currents [through Io] are large enough to cause ohmic heating ... currents ... contract down to narrow paths which can be kept hot, and along which the conductivity is high. Tidal heating [ensures] that the interior of Io has a very low eletrical resistance, causing a negligible extra amount of heat to be deposited by this current. ... [T]he outermost layers, kept cool by radiation into space [present] a large resistance and [result in] a concentration of the current into hotspots ... rock resistivity [and] contact resistance ... contribute to generate high temperatures on the surface. [These are the] conditions of electric arcs [that can produce] temperatures up to ionization levels ... several thousand kelvins".

"[T]he outbursts ... seen [on the surface may also be] the result of the large current ... flowing in and out of the domain of Io ... Most current spots are likely to be volcanic calderas, either provided by tectonic events within Io or generated by the current heating itself. ... [A]s in any electric arc, very high temperatures are generated, and the locally evaporated materials ... are ... turned into gas hot enough to expand at a speed of 1 km/s."

"Field-aligned equatorial electron beams [have been] observed within Jupiter’s middle magnetosphere. ... the Jupiter equatorial electron beams are spatially and/or temporally structured (down to <20 km at auroral altitudes, or less than several minutes), with regions of intense beams intermixed with regions absent of such beams."

"Jovian electrons, both at Jupiter and in the interplanetary medium near Earth, have a very hard spectrum that varies as a power law with energy (see, e.g., Mewaldt et al. 1976). This spectral character is sufficiently distinct from the much softer solar and magnetospheric electron spectra that it has been used as a spectral filter to separate Jovian electrons from other sources ... A second Jovian electron characteristic is that such electrons in the interplanetary medium tend to consist of flux increases of several days duration which recur with 27 day periodicities ... A third feature of Jovian electrons at 1 AU is that the flux increases exhibit a long-term modulation of 13 months which is the synodic period of Jupiter as viewed from Earth".

Jovian electrons propagate "along the spiral magnetic field of the interplanetary medium [from Jupiter and its magnetosphere to the Sun]".

Hypotheses

 * 1) Two or more geographical observatories at opposite locations on Earth reporting the same phenomena may be observing source effects.

"It would be interesting to see the response of ESO detectors to a control group of known satellites, each having a different rotation rate."