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Though obsidian is usually dark in color, similar to mafic rocks such as basalt, the composition of obsidian is extremely felsic. Obsidian consists mainly of SiO 2 ( silicon dioxide ), usually 70% by weight or more; the remainder consists of variable amounts of other oxides, mostly oxides of aluminum, iron, potassium, sodium and calcium.
Satellite photograph of a mesa in the Cydonia region of Mars, often called the "Face on Mars" and cited as evidence of extraterrestrial habitation. Pareidolia (/ ˌ p ær ɪ ˈ d oʊ l i ə, ˌ p ɛər-/; [1] also US: / ˌ p ɛər aɪ-/) [2] is the tendency for perception to impose a meaningful interpretation on a nebulous stimulus, usually visual, so that one detects an object, pattern, or ...
The prehistoric rock engravings of the Fontainebleau Forest are an abundant collection of rock art discovered among the sandstone boulders of the Fontainebleau Forest. Several thousand petroglyphs have been discovered in the forest, with earliest dating to the Paleolithic (very few examples), roughly 2000 to the early Mesolithic and almost 300 ...
The undated photo was likely taken awhile ago, since The Rock has sported a more clean-shaven look in recent months. Check out that Blackberry. We're guessing 2007, maybe 2008.
Sailing stones (also called sliding rocks, walking rocks, rolling stones, and moving rocks) are part of the geological phenomenon in which rocks move and inscribe long tracks along a smooth valley floor without animal intervention. The movement of the rocks occurs when large, thin sheets of ice floating on an ephemeral winter pond break up in ...
Rocks formations and the Dedo de Deus (God's Finger) peak in the background, Serra dos Órgãos National Park, Rio de Janeiro state, Brazil Raouché or Pigeons' Rock in Beirut, Lebanon Druid Arch, Canyonlands National Park, Utah, US View of Meteora, Greece Rock formations in Ongamira Valley, Sierras de Córdoba, Argentina Belogradchik Rocks, Balkan Mountains, Bulgaria "Jaws", an erosional fin ...
The areas that underwent glaciation were approximately those where the Great Unconformity is located today. When glaciers move, they drag and erode sediment away from the underlying rock. This would explain how a large section of rock was taken away from widespread areas around the same time. [citation needed]
The following is a list of rock types recognized by geologists.There is no agreed number of specific types of rock. Any unique combination of chemical composition, mineralogy, grain size, texture, or other distinguishing characteristics can describe a rock type.