Radiation astronomy/Rocks

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This Sin-Kamen (Blue Rock) near Lake Pleshcheyevo used to be a Meryan shrine Credit: Viktorianec.
This is a blue rock, probably various copper minerals, from the Berkeley hills near San Francisco, California. Credit: Looie496.
This is an approximately natural color picture of the asteroid 243 Ida on August 28, 1993. Credit: NASA/JPL.

Sin-Kamen (Синь-Камень, in Russian literally – Blue Stone, or Blue Rock) is a type of pagan sacred stones, widespread in Russia, in areas historically inhabited by both Eastern Slavic (Russian), and Uralic tribes (Merya, Muroma[1]).

While in the majority of cases, the stones belonging to the Blue Stones type, have a black, or dark gray color, this particular stone [in the image] does indeed look dark blue, when wet.[2]

"Several types of rock surface materials can be recognized at the two sites [Viking Lander 1 and Viking Lander 2]; dark, relatively 'blue' rock surfaces are probably minimally weathered igneous rock, whereas bright rock surfaces, with a green/(blue + red) ratio higher than that of any other surface material, are interpreted as a weathering product formed in situ on the rock."[3]

At second right is an approximately natural color image of the asteroid 243 Ida. "There are brighter areas, appearing bluish in the picture, around craters on the upper left end of Ida, around the small bright crater near the center of the asteroid, and near the upper right-hand edge (the limb). This is a combination of more reflected blue light and greater absorption of near infrared light, suggesting a difference in the abundance or composition of iron-bearing minerals in these areas."[4]

"The [Sloan Digital Sky Survey] SDSS “blue” asteroids are related to the C-type (carbonaceous) asteroids, but not all of them are C-type. They are a mixture of C-, E-, M-, and P-types."[5]

X-rays[edit]

The image contains a 27.70 g fragment of the Carancas meteorite fall. The scale cube is 1 cm3. Credit: Meteorite Recon.

On September 20, the X-Ray Laboratory at the Faculty of Geological Sciences, Mayor de San Andres University, La Paz, Bolivia, published a report of their analysis of a small sample of material recovered from the impact site. They detected iron, nickel, cobalt, and traces of iridium — elements characteristic of the elemental composition of meteorites. The quantitative proportions of silicon, aluminum, potassium, calcium, magnesium, and phosphorus are incompatible with rocks that are normally found at the surface of the Earth.[6]

In X-ray wavelengths, many scientists are investigating the scattering of X-rays by interstellar dust, and some have suggested that astronomical X-ray sources would possess diffuse haloes, due to the dust.[7]

Volcanic bombs[edit]

This is an accretionary lava ball. Credit: J. D. Griggs, USGS HVO.
This is a volcanic bomb found in the Mojave Desert National Preserve by Rob McConnell. Credit: Wilson44691.
This is a picture of a lavabomb at Strohn, Germany. Credit: Jhintzbe.

Def. "distinctively shaped [natural] projectiles ... which acquired their shape essentially before landing"[8] are called bombs.

Def. a bomb "ejected from a volcanic vent"[8] 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."[9]

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.

References[edit]

  1. И.Д. Маланин. Материалы разведки Синих камней Подмосковья в 2003 году // Краеведение и регионоведение. Межвузовский сборник научных трудов. ч.1. Владимир, 2004. (Russian)
  2. Бердников, В. Синий камень Плещеева озера // Наука и жизнь. – 1985. – № 1. – С. 134–139. (Russian)
  3. Lua error in Module:Citation/CS1 at line 3723: bad argument #1 to 'pairs' (table expected, got nil).
  4. Lua error in Module:Citation/CS1 at line 3723: bad argument #1 to 'pairs' (table expected, got nil).
  5. F Yoshida, T Nakamura (June 2007). "Subaru main belt asteroid survey (SMBAS)—size and color distributions of small main-belt asteroids". Planetary and Space Science 55 (9): 1113-25. doi:10.1016/j.pss.2006.11.016. http://www.sciencedirect.com/science/article/pii/S0032063306003357. Retrieved 2013-06-01. 
  6. Mario Blanco Cazas, "Informe Laboratorio de Rayos X — FRX-DRX" (in Spanish), Universidad Mayor de San Andres, Facultad de Ciencias Geologicas, Instituto de Investigaciones Geologicas y del Medio Ambiente, La Paz, Bolivia, September 20, 2007. Retrieved October 10, 2007.
  7. Smith RK, Edgar RJ, Shafer RA (Dec 2002). "The X-ray halo of GX 13+1". Ap J 581 (1): 562–69. doi:10.1086/344151. http://iopscience.iop.org/0004-637X/581/1/562. 
  8. 8.0 8.1 G. P. L. Walker (April 1969). "The breaking of magma". Geological Magazine 106 (02): 166-73. doi:10.1017/S0016756800051979. http://journals.cambridge.org/production/action/cjoGetFulltext?fulltextid=4626560. Retrieved 2012-10-13. 
  9. Lua error in Module:Citation/CS1 at line 3723: bad argument #1 to 'pairs' (table expected, got nil).