A form of cross-bedding in which the direction of slope alternates, as a result of oscillatory flow. Chemical symbol for the element hafnium. A pillar of rock produced by erosion. A distinct layer in a soil , formed by pedogenetic processes. Article : Soils and paleosols. A large group of metamorphic rocks produced from sedimentary rocks by contact metamorphism.
A stationary point of high volcanic activity above which plates pass, creating an aseismic ridge. Decaying organic matter in soil. Coal produced by the deposition of land plants in swamps, as opposed to sapropelic coal. Having to do with hot water. A time at which sheet glaciers are present on some regions of the Earth's surface. Synonym for continental glacier.
Rock formed by the cooling of lava in which case the rock is said to be extrusive or magma in which case the rock is said to be intrusive. A fossil of a species that was sufficiently widely distributed that its fossils can be used to correlate the deposition of fossils and sediments in widely separated locations. Articles : Index fossils , Fossils and absolute dating. Any mineral which forms only at certain temperatures and pressures, and which can therefore be used as an index to the conditions under which certain metamorphic rocks were formed.
A species suitable for the production of index fossils. Article : Index fossils. Of an element , unable to participate in chemical reactions. Article : K-Ar dating. A synonym for chain silicate. The quantity per area of solar radiation reaching a given location. Articles : Milankovitch cycles , Climate models. Incapable of becoming dissolved.
Ripples caused by two currents flowing one after the other at or near right-angles to one another. A time of glacial retreat during an ice age. A complex pattern of sediments in which different sedimentary types e. A drainage pattern typical of deserts , in which rivers flow into the desert and evaporate. Rock formed by magma penetrating country rock but not reaching the surface as lava.
As the magma will cool slowly, intrusive rock can be distinguished from extrusive rock by the relatively large size of the crystals of which the former is composed. Such rock is said to intrude into the country rock. Grading where the size of clasts varies from small clasts at the bottom of a layer to large clasts at the top. An atom which has gained or lost electrons , giving it a negative or positive charge respectively.
A bond between atoms in which one atom donates electrons to another. Minerals containing both iron and oxygen, as the name suggests: examples include hematite and goethite. A form of radiometric dating involving the construction of an isochron diagram.
Articles : Rb-Sr dating , Other isochron methods. A graph showing the isotope ratios of various minerals found in the same rock , used in isochron dating. The process whereby land which has formerly been depressed by overlying weight for example of an ice sheet rises when the weight is removed. Atoms are classified into isotopes according to their atomic number and their atomic weight.
Chemical symbol for the element potassium. Articles : Chemistry for geologists , K-Ar dating. Potassium-argon dating, a form of radiometric dating.
The distinctive landscape produced by the chemical weathering of limestone. Article : Other isochron methods. A small lake formed by glacial outwash being deposited around a largish chunk of ice left behind by a retreating glacier ; when the residual chunk of ice melts, this leaves a depression which will typically fill with water, producing a kettle. Chemical symbol for the element lanthanum. Lanthanum-barium dating, a form of radiometric dating. Lanthanum-cerium dating, a form of radiometric dating.
An intrusion between two strata , similar to a sill but thicker and lens-shaped. Having to do with lakes.
Article : Lakes. An inland body of water fed by rivers, streams, or sometimes by seepage of groundwater. A very thin bed , no more than a few millimeters thick.
Sediment which accumulates along the sides of a valley glacier , having fallen or been scraped off the walls of the valley. A soil type characteristic of a tropical climate alternating between a monsoon season and a dry season. Article : Sediments and climate. Silicate minerals in which the silicate tetrahedra are bonded together to form a three-dimensional lattice.
Molten rock which has reached the surface, as opposed to magma , which is sill trapped beneath it. Igneous rock formed by lava flowing on the surface. Ions dissolved in water as a result of chemical weathering ; as opposed to residual minerals. The side of a mountain, dune , antidune , or generally any hill-shaped geological feature, which is on the down-stream side of a current of wind or water.
The opposite of stoss. Abbreviation for last glacial maximum. The softest form of coal ; the next stage in the formation of coal from peat after peat itself. Rock formed from calcium carbonate , usually in the form of calcite. Trees the growth of which we would expect to be limited by a single factor such as temperature because they grow in an environment with an abundant supply of other factors necessary for growth such as rainfall.
Article : Dendroclimatology. The arrangement of chain silicates in parallel lines in certain metamorphic rocks formed under pressure: the pressure forces these silicates to orientate themselves at right-angles to the direction of pressure. The conversion of sediment into a sedimentary rock by such processes as compaction and cementation.
The Earth's crust together with that portion of the mantle which, like the crust, is brittle and elastic rather than plastic and ductile. Having to do with the coast. Fine wind-borne sediment produced by the action of glaciers. Bars of sediment running parallel to a beach. The component of a nearshore current that flows parallel to the shoreline.
The motion of sediment along the shore as a result of the fact that waves that approach the shore obliquely will recede from it at right-angles to the shoreline. A type of seismic wave which travels along the surface of the Earth rather than through it. Chemical symbol for the element lutetium.
Lutetium-hafnium dating, a form of radiometric dating. A rock rich in magnesium and iron, and poor in quartz and feldspar. Molten rock which has not reached the surface, as opposed to lava. Some authors will define magma as any molten rock , in which case it would be proper to say that " lava is magma on the surface". However, in this text I have preferred the usage which makes magma and lava two distinct non-overlapping categories of molten rock.
A zone of ultramafic rock lying below the Earth's crust and above its core. A column of hot rock rising in the mantle below a hotspot. A metamorphic rock formed by the metamorphism of limestone. Rock which does not display bedding in the case of sedimentary rocks or foliation in the case of metamorphic rocks , giving the rock a uniform and homogeneous appearance.
This term is not used in our articles, so as to avoid confusion with the common use of "massive" to mean "very big"; we have instead used more transparent terms such as "unbedded". Erosion caused by gravity. A synonym for groundmass. A broad loop in a stream or river. A stream which flows in a series of meanders. Weathering caused by mechanical processes that break up a rock, as opposed to chemical weathering.
A moraine formed by the union of two lateral moraines when two valley glaciers flow together to forms a single glacier.
The degree of metamorphism undergone by a metamorphic rock. The gas C H 4 , a potent greenhouse gas. Chemical symbol for the element magnesium. A group of sheet aluminosilicate minerals. Articles : Igneous rocks , Metamorphic rocks. Elevated sea-floor on either side of a mid-ocean rift. Articles : Sea floor spreading , Sea level variations.
The rift between two plates at which sea floor spreading occurs. Periodic changes in the inclination of the Earth's axis and the shape of its orbit. A solid with a particular chemical composition and structure.
Articles : Minerals , Silicate minerals. Anything which is like a mineral in some respects but doesn't quite fit the definition. A graph showing the composition of a rock on which the plotted points will fall in a straight line if the rock was produced by the mixing of different sources of magma.
Article : Rb-Sr dating. A fossil formed when sediment is packed around organic remains, which are then destroyed, leaving a void in the sediment in the shape of the remains. A collection of atoms bonded together. A deposit of till. A small-scale geological structures produced in mud as it dries.
Rock formed from clay or silt which is not bedded : lithified mud which is bedded is known as shale. A rock produced at depth by the ation of two sides of a fault rubbing against one another, having a distinctive "grain" indicating the direction of motion of the fault.
Chemical symbol for the element sodium. Chemical symbol for the element neodymium. Chemical symbol for the element neon. The zone in which the sea bed is affected by waves. A silicate mineral in which the silicate tetrahedra are isolated from one another. A particle with no charge and approximately the same mass as a proton ; together with protons , neutrons make up the nucleus of an atom.
An unconformity in which the older rocks are igneous or metamorphic. A dip-slip fault in which the hanging wall moves downwards relative to the foot wall. The polarity of the Earth's magnetic field as it is at present. Note that there is nothing particularly normal about this state of affairs. The opposite of reversed polarity. A fragment of shell or stone around which an ooid forms. Article : Ooids and oolite. The core of an atom , consisting of protons and neutrons.
Chemical symbol for the element oxygen. Articles : Chemistry for geologists , Banded iron formations. A small lake found in a desert. A process in which one platecolliding with another is thrust over it instead of beneath it; the opposite of subduction.
Article : Ophiolites. A fault which combines elements of a dip-slip fault and a strike-slip fault. Felsic volcanic glass. A silicate mineral with the chemical formula Mg , Fe 2 Si O 4 and an orthorhombic crystal system.
Articles : Minerals , Igneous rocks , Structure of the Earth. A small roughly spherical particle consisting of calcium carbonate layers formed around a nucleus of sand or shell. Required the action of waves for formation, and is therefore formed in shallow seas. Limestone composed of ooids cemented together. Either a rock formed from ooids , or a single ooid , depending on context.
Synonym for oolite. Amorphous hydrated silica , of which the precious stone known as opal is only one particularly pretty example. The depth at which siliceous material will dissolve faster than it is deposited; hence, the depth below which marine chert will not form. A section of oceanic crust which has been thrust up above sea-level. A synonym for neosilicate. The formation of mountains; or the faulting and folding of a large area by lateral pressure; or the formation of mountains by this process.
Article : Orogeny. Chemical symbol for the element osmium. The washing back and forth of water on the foreshore as a result of the action of the tide. Light sediment carried by meltwater from the ablation zone of a glacier. A flat area of outwash sediment in front of a glacier. A crescent-shaped lake formed when a meandering stream changes its course, leaving one of its meanders cut off from the stream.
A reef -forming bivalve. The chemical symbol for the element protactinium. A type of lava flow, or the cooled and solidified rock produced by it, characterized by a ropey and billowy surface texture. The study of ancient climates. Ancient currents of wind and water the direction of which can be deduced from the analysis of sedimentary rocks.
Article : Paleocurrents. A form of absolute dating based on analysis of the paleomagnetic data in the rocks. Article : Paleomagnetic dating. The geological record of the past history of the Earth's magnetic field. Articles : Geomagnetic reversals , Sea floor spreading , Paleomagnetic dating.
Fossilized soil. The last supercontinent to exist, prior to its rifting and the formation of the Atlantic Ocean. A supercontinent that existed before Pangea. An unconformity without an erosional surface.
A radioactive isotope which undergoes radioactive decay to produce a daughter isotope. The original rock from which a metamorphic rock is formed by metamorphism. Chemical symbol for the element lead. Lead-lead dating, a form of radiometric dating. Waterlogged and partially decomposed vegetable matter.
Note that in geological usage peat does not just refer to gardeners' peat formed from sphagnum moss but to any vegetable matter that has undergone peatification. Peat is the sediment from which coal is formed. The partial decomposition of waterlogged vegetable matter, turning it into peat. The process of turning sediment into soil by chemical weathering and the activity of organisms plants growing in it, burrowing animals such as worms, the addition of humus etc.
Having to do with the open sea. Articles : Marine sediments , Index fossils. Fine-textured sediment deposited on the abyssal plain. An ultramafic igneous rock consisting mainly of olivine with a little pyroxene and amphibole. A tabular arrangement of the elements which gives insight into their chemical properties.
A process forming mineralized fossils in which the voids in the original material are filled by minerals. A process forming mineralized fossils in which they undergo both replacement and permineralization. An igneous rock is said to be phaneritic if the crystals in it are large enough to be seen with the naked eye. The opposite of aphenatic. Whether a substance is solid, liquid, or gas; if solid, its crystal structure or lack thereof.
A large crystal embedded in the more finely-grained ground mass of a porphyritic rock. The rejection a priori of the existence of the supernatural; a position completely unnecessary to the practice of geology. Article : Actualism. A synonym for sheet silicate. Basalt with a distinctive shape consisting of a set of "pillows"; formed underwater as a result of the more rapid cooling of lava on contact with water. Articles : Igneous rocks , Ophiolites. A very thin lamina of very fine clasts , formed in and characteristic of aeolian sand dunes.
A material is said to be plastic if it does not recover from stress : that is, having been squeezed by stress into a given form, it retains that form when the stress is removed. The opposite of elastic. A flat-bottomed basin in a desert which periodically fills with water to form a shallow temporary lake. Alternative term for intrusive rock. A piece of the lithosphere bounded by faults. The study of the motion of the Earth's plates. The Paleoclimate Modeling Intercomparison Project, a project comparing results from climate models with the evidence from paleoclimatic proxies.
A bar of sediment formed on the inner bank of a meander. Two minerals having the same chemical formula but a different crystal structure are said to be polymorphs. A small lake. Of a rock , containing some large crystals embedded in a more finely-grained ground mass.
When a chemical formerly dissolved in water settles out of it as a solid sediment , this is called precipitation. Preceding written human history; the fairly arbitrary line before which organic remains are considered to be fossils. Term sometimes used for igneous rock. The principle that when one geological feature cuts through another, the former is the younger and the latter is the older of the two features.
Roughly speaking, the principle that if the fauna and flora in one location are found in one stratigraphic order, the same species will not be found in a different order in another location. The principle in physics that a wave traveling through a medium will take the quickest route between two points. The principle that when sediment is laid down, it will extend continuously until either it meets an obstacle or tapers off with increasing distance from the source of the sediment.
The principle that when sediment is laid down, it is usually laid down more or less flat. The principle that when sediment is laid down, the sediment most recently deposited will be on the top. A lake fed by meltwater from a glacier. It is on these humid fertile areas that the Veiled Chameleon thrives. Most of the rain is deposited before reaching the top of the mountain region, making the plateau much drier and less humid.
Also the temperatures are cooler with frost sometimes occurring in the winter months. In Western Yemen the three main areas Veiled Chameleons can be found are:. The narrow coastal plains of Western Yemen, bordering the Red Sea are primarily hot with little or no rainfall less than 50mm annually , and are prone to sandstorms. Temperatures often exceed F 38 C with high humidity.
In these semi-desert conditions Calyptratus can be found next to the main watercourses Waddi's of which there are many. Although many of the Waddi's dry out during the hotter months the damp soil along the edges makes the. Picture above is a typical waddi in Western Yemen. Notify me of new posts via email. This site uses Akismet to reduce spam. Learn how your comment data is processed. Wild Horse Freedom Federation, Inc.
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A reef -forming bivalve. No, I love getting all No.2 in D Major - Schubert* / Imogen Cooper - Schubert Live • Volume Two and sweaty, covered in dirt and smelling like a hippo. An outdated and inaccurate term for felsic rock. Articles : Geomagnetic La Bomba - Various - Playa Total 3: Todos Los Éxitos Del VeranoSea floor spreadingPaleomagnetic dating. Sediment which accumulates along the sides of a valley glacierhaving fallen or been scraped off the walls of the valley. Occasionally someone would joke about wanting a cheeseburger or a cold beer or a shower. A group of marine organisms. Article : Ice ages. Articles : DendrochronologyDendroclimatology.
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