Xenolith. Although the term xenolith is most commonly associated with igneous inclusions, a broad definition could include rock fragments which have become encased in sedimentary rock.
Xenoliths are sometimes found in recovered meteorites. To be considered a true xenolith, the included rock must be identifiably different from the rock in which it is enveloped; an included rock of similar type is called an autolith or a cognate inclusion. The large scale inclusion of foreign rock strata at the margins of an igneous intrusion is called a roof pendant. Examples Large and rather unusual xenolith of sandstone (probably from the Albee Fm.) within the Fairlee Pluton in VermontPeridotite (green) mantle xenolith within a (dark) volcanic bomb from the Vulkan-Eifel, Germany. References Geomorphology. A natural arch produced by erosion of differentially weathered rock in Jebel Kharaz (Jordan) Surface of the Earth, showing higher elevations in red color.
Geomorphology (from Greek: γῆ, ge, "earth"; μορφή, morfé, "form"; and λόγος, logos, "study") is the scientific study of the origin and evolution of topographic and bathymetric features created by physical or chemical processes operating at or near Earths surface. Geomorphologists seek to understand why landscapes look the way they do, to understand landform history and dynamics and to predict changes through a combination of field observations, physical experiments and numerical modeling. Geomorphology is practiced within physical geography, geology, geodesy, engineering geology, archaeology and geotechnical engineering. This broad base of interest contributes to many research styles and interests within the field.
Overview Wave action and water chemistry lead to structural failure in exposed rocks History Processes Model theory. This article is about the mathematical discipline.
For the informal notion in other parts of mathematics and science, see Mathematical model. Model theory recognises and is intimately concerned with a duality: It examines semantical elements (meaning and truth) by means of syntactical elements (formulas and proofs) of a corresponding language. To quote the first page of Chang and Keisler (1990): universal algebra + logic = model theory. Model theory developed rapidly during the 1990s, and a more modern definition is provided by Wilfrid Hodges (1997): although model theorists are also interested in the study of fields. Mathematical logic. For Quine's theory sometimes called "Mathematical Logic", see New Foundations.
Mathematical logic is a subfield of mathematics exploring the applications of formal logic to mathematics. It bears close connections to metamathematics, the foundations of mathematics, and theoretical computer science. The unifying themes in mathematical logic include the study of the expressive power of formal systems and the deductive power of formal proof systems. Mathematical logic is often divided into the fields of set theory, model theory, recursion theory, and proof theory. These areas share basic results on logic, particularly first-order logic, and definability. In computer science (particularly in the ACM Classification) mathematical logic encompasses additional topics not detailed in this article; see Logic in computer science for those. Universal algebra. Universal algebra (sometimes called general algebra) is the field of mathematics that studies algebraic structures themselves, not examples ("models") of algebraic structures.
For instance, rather than take particular groups as the object of study, in universal algebra one takes "the theory of groups" as an object of study. Basic idea where J is an infinite index set, thus leading into the algebraic theory of complete lattices.
Lithos. Lithos is a glyphic sans-serif typeface designed by Carol Twombly in 1989 for Adobe Systems.
Lithos is inspired by the unadorned, geometric letterforms of the engravings found on Ancient Greek public buildings. The typeface consists of only capital letters, and comes in five weights, with no italics. Publications associated with African, African-American and Southwestern cultures have used Lithos for its "ethnic" feel, even if it is the wrong ethnicity. Lithos has also become something of a generic stand-in whenever a "primitive" feel is desired. For this reason, Lithos has been compared to Rudolf Koch's typeface, Neuland, which was originally intended to be a modern reinterpretation of blackletter, but received similarly broad use. Lithos Pro Lithosphere. The tectonic plates of the lithosphere on Earth Earth's lithosphere Earth's lithosphere includes the crust and the uppermost mantle, which constitute the hard and rigid outer layer of the Earth.
The lithosphere is subdivided into tectonic plates. Silicon. Not to be confused with the silicon-containing synthetic polymer silicone.
Silicon is a chemical element with symbol Si and atomic number 14. A hard and brittle crystalline solid with a blue-gray metallic luster, it is a tetravalent metalloid. It is a member of group 14 in the periodic table, along with carbon above it and germanium, tin, lead, and flerovium below. It is rather unreactive, though less so than germanium, and has great chemical affinity for oxygen; as such, it was first prepared and characterized in pure form only in 1823 by Jöns Jakob Berzelius. Silicon is the eighth most common element in the universe by mass, but very rarely occurs as the pure element in the Earth's crust.
Elemental silicon also has a large impact on the modern world economy.