Glossary
- Page ID
- 21369
\( \newcommand{\vecs}[1]{\overset { \scriptstyle \rightharpoonup} {\mathbf{#1}} } \)
\( \newcommand{\vecd}[1]{\overset{-\!-\!\rightharpoonup}{\vphantom{a}\smash {#1}}} \)
\( \newcommand{\id}{\mathrm{id}}\) \( \newcommand{\Span}{\mathrm{span}}\)
( \newcommand{\kernel}{\mathrm{null}\,}\) \( \newcommand{\range}{\mathrm{range}\,}\)
\( \newcommand{\RealPart}{\mathrm{Re}}\) \( \newcommand{\ImaginaryPart}{\mathrm{Im}}\)
\( \newcommand{\Argument}{\mathrm{Arg}}\) \( \newcommand{\norm}[1]{\| #1 \|}\)
\( \newcommand{\inner}[2]{\langle #1, #2 \rangle}\)
\( \newcommand{\Span}{\mathrm{span}}\)
\( \newcommand{\id}{\mathrm{id}}\)
\( \newcommand{\Span}{\mathrm{span}}\)
\( \newcommand{\kernel}{\mathrm{null}\,}\)
\( \newcommand{\range}{\mathrm{range}\,}\)
\( \newcommand{\RealPart}{\mathrm{Re}}\)
\( \newcommand{\ImaginaryPart}{\mathrm{Im}}\)
\( \newcommand{\Argument}{\mathrm{Arg}}\)
\( \newcommand{\norm}[1]{\| #1 \|}\)
\( \newcommand{\inner}[2]{\langle #1, #2 \rangle}\)
\( \newcommand{\Span}{\mathrm{span}}\) \( \newcommand{\AA}{\unicode[.8,0]{x212B}}\)
\( \newcommand{\vectorA}[1]{\vec{#1}} % arrow\)
\( \newcommand{\vectorAt}[1]{\vec{\text{#1}}} % arrow\)
\( \newcommand{\vectorB}[1]{\overset { \scriptstyle \rightharpoonup} {\mathbf{#1}} } \)
\( \newcommand{\vectorC}[1]{\textbf{#1}} \)
\( \newcommand{\vectorD}[1]{\overrightarrow{#1}} \)
\( \newcommand{\vectorDt}[1]{\overrightarrow{\text{#1}}} \)
\( \newcommand{\vectE}[1]{\overset{-\!-\!\rightharpoonup}{\vphantom{a}\smash{\mathbf {#1}}}} \)
\( \newcommand{\vecs}[1]{\overset { \scriptstyle \rightharpoonup} {\mathbf{#1}} } \)
\( \newcommand{\vecd}[1]{\overset{-\!-\!\rightharpoonup}{\vphantom{a}\smash {#1}}} \)
\(\newcommand{\avec}{\mathbf a}\) \(\newcommand{\bvec}{\mathbf b}\) \(\newcommand{\cvec}{\mathbf c}\) \(\newcommand{\dvec}{\mathbf d}\) \(\newcommand{\dtil}{\widetilde{\mathbf d}}\) \(\newcommand{\evec}{\mathbf e}\) \(\newcommand{\fvec}{\mathbf f}\) \(\newcommand{\nvec}{\mathbf n}\) \(\newcommand{\pvec}{\mathbf p}\) \(\newcommand{\qvec}{\mathbf q}\) \(\newcommand{\svec}{\mathbf s}\) \(\newcommand{\tvec}{\mathbf t}\) \(\newcommand{\uvec}{\mathbf u}\) \(\newcommand{\vvec}{\mathbf v}\) \(\newcommand{\wvec}{\mathbf w}\) \(\newcommand{\xvec}{\mathbf x}\) \(\newcommand{\yvec}{\mathbf y}\) \(\newcommand{\zvec}{\mathbf z}\) \(\newcommand{\rvec}{\mathbf r}\) \(\newcommand{\mvec}{\mathbf m}\) \(\newcommand{\zerovec}{\mathbf 0}\) \(\newcommand{\onevec}{\mathbf 1}\) \(\newcommand{\real}{\mathbb R}\) \(\newcommand{\twovec}[2]{\left[\begin{array}{r}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\ctwovec}[2]{\left[\begin{array}{c}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\threevec}[3]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\cthreevec}[3]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\fourvec}[4]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\cfourvec}[4]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\fivevec}[5]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\cfivevec}[5]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\mattwo}[4]{\left[\begin{array}{rr}#1 \amp #2 \\ #3 \amp #4 \\ \end{array}\right]}\) \(\newcommand{\laspan}[1]{\text{Span}\{#1\}}\) \(\newcommand{\bcal}{\cal B}\) \(\newcommand{\ccal}{\cal C}\) \(\newcommand{\scal}{\cal S}\) \(\newcommand{\wcal}{\cal W}\) \(\newcommand{\ecal}{\cal E}\) \(\newcommand{\coords}[2]{\left\{#1\right\}_{#2}}\) \(\newcommand{\gray}[1]{\color{gray}{#1}}\) \(\newcommand{\lgray}[1]{\color{lightgray}{#1}}\) \(\newcommand{\rank}{\operatorname{rank}}\) \(\newcommand{\row}{\text{Row}}\) \(\newcommand{\col}{\text{Col}}\) \(\renewcommand{\row}{\text{Row}}\) \(\newcommand{\nul}{\text{Nul}}\) \(\newcommand{\var}{\text{Var}}\) \(\newcommand{\corr}{\text{corr}}\) \(\newcommand{\len}[1]{\left|#1\right|}\) \(\newcommand{\bbar}{\overline{\bvec}}\) \(\newcommand{\bhat}{\widehat{\bvec}}\) \(\newcommand{\bperp}{\bvec^\perp}\) \(\newcommand{\xhat}{\widehat{\xvec}}\) \(\newcommand{\vhat}{\widehat{\vvec}}\) \(\newcommand{\uhat}{\widehat{\uvec}}\) \(\newcommand{\what}{\widehat{\wvec}}\) \(\newcommand{\Sighat}{\widehat{\Sigma}}\) \(\newcommand{\lt}{<}\) \(\newcommand{\gt}{>}\) \(\newcommand{\amp}{&}\) \(\definecolor{fillinmathshade}{gray}{0.9}\)| Words (or words that have the same definition) | The definition is case sensitive | (Optional) Image to display with the definition [Not displayed in Glossary, only in pop-up on pages] | (Optional) Caption for Image | (Optional) External or Internal Link | (Optional) Source for Definition |
|---|---|---|---|---|---|
| (Eg. "Genetic, Hereditary, DNA ...") | (Eg. "Relating to genes or heredity") |  |
The infamous double helix | https://bio.libretexts.org/ | CC-BY-SA; Delmar Larsen |
| Word(s) | Definition | Image | Caption | Link | Source |
|---|---|---|---|---|---|
| earthquake weather | An informal term for a phenomenon which does not exist; there is no connection between weather conditions and earthquakes | ||||
| three layer cake | An informal term to describe the soil disrupted by the 1700 Cascadia quake | ||||
| abrasion | The grinding and scarping of a rock surface by the friction and impact of rock particles carried by water, wind, and/or ice. | ||||
| accreted terrane | An island arc or microcontinent that has been accreted to a continent. | ||||
| accretion | The accumulation of material onto another object. In geology: the accretion of material to the overriding plate during subduction. | ||||
| accretionary wedge | A mass of material accreted from the top of the subducting slab at a suduction zone. | ||||
| accretionary prism | A mass of material accreted from the top of the subducting slab at a suduction zone. | ||||
| active margin | A plate boundary close to a continental margin | ||||
| age | The smallest geochronologic unit by which the geologic time scale is divided. | ||||
| alkalinity | The measure of the pH of material. pH = 7 is neutral. Materials with pH>7 are alkaline. | ||||
| allochthon | A block of rocks that have been transported a great distance from where they formed. | ||||
| alluvial fan | A triangle-shaped deposit of gravel, sand, and even smaller pieces of sediment. |  |
Alluvial fans developing in a half-graben. | CC BY-SA 3.0; Mikenorton | |
| alluvium | A deposit of clay, silt, sand, and gravel left by flowing streams in a river valley or delta, typically producing fertile soil. | ||||
| Alquist-Priolo Act (AP Act) | California legislation involving restrictions in building near faults; enacted following the 1971 San Fernando Valley quake | ||||
| amphibolite | A rock composed largely or dominantly of minerals of the amphibole group; can be applied to rocks of either igneous or metamorphic origin | ||||
| amu | (atomic mass unit); A unit of mass used for expressing atomic and molecular weights. | ||||
| Andean type subduction | Oceanic lithosphere subducts beneath continental lithosphere producing a continental arc mountain range. | ||||
| andesite | An intermediate, extrusive igneous rock. | ||||
| andesitic | Of a composition similar to andesite. | ||||
| angle of repose | The steepest angle of descent or dip relative to the horizontal plane on which the material can be piled without slumping | ||||
| angular unconformity | Where horizontally parallel strata of sedimentary rock are deposited on tilted and eroded layers, producing an angular discordance with the overlying horizontal layers. | ||||
| anthropogenic | Caused by Homo sapiens | ||||
| anticline | A fold that is generally convex upward, whose core contains the stratigraphically older rocks. | ||||
| antiform | A fold that is convex upward and for which the ages of the rocks are unknown. | ||||
| aphanitic | Fine grained igneous texture; the mineral crystals are too small to be seen with the naked eye. | ||||
| aquifer | A body of permeable rock which can contain or transmit groundwater. | ||||
| Arctodus simus | The "short-faced bear," an extinct Pleistocene bear much larger than modern grizzly or polar bears | ||||
| arete | A sharp ridge left by the erosion of glaciers on either side. | ||||
| ARkstrom | A term used by the USGS to describe giant atmospheric river events, such as the flooding of 1861-1862 | ||||
| arokosic | A sandstone with a considerable amount of feldspar (at least 25%). | ||||
| artificially induced seismicity | earthquakes created by human activity (e.g., injection of fluids into hot rock in petroleum fracking) | ||||
| aseismic creep | ground movement along faults without corresponding earthquakes | ||||
| ash | The smallest size of particle ejected from a volcanic eruption; particles less than 2mm in diameter, composed of rock, mineral and glass particles. | ||||
| assimilation | In geology: country rock with a different composition is added to magma. | ||||
| asthenosphere | A layer in Earth's mantle known for its ductility and thought to be a key to the mechanics of plate tectonics | ||||
| atmospheric river | A weather phenomenon involving multiple successive storms flowing into the West Coast, often resulting in flooding in California | ||||
| atoll | A ring-shaped island or series of islands, made of coral, surrouding a lagoon. | ||||
| atomic mass | The total number of protons and neutrons in an atom. | ||||
| atomic mass unit | (amu); A unit of mass used for expressing atomic and molecular weights. | ||||
| atomic number | The number of protons in an atom. | ||||
| axial plane | See axial surface. A planar surface that connects the hinge lines of the strata in a fold | ||||
| axial surface | See axial plane. A surface that connects the hinge lines of the strata in a fold. | ||||
| back-arc | Located adjacent to a volcanic arc, on the side away from the subduction zone. | ||||
| bajada | A broad slope of alluvial material at the foot of an escarpment or mountain. | ||||
| basalt | A mafic, extrusive igneous rock. | ||||
| basaltic | Of a composition similar to basalt. | ||||
| batholith | A very large body of intrusive igneous rock, composed of multiple plutons of similar composition and appearance. | ||||
| bedload | The discharge of sediment particles which are too heavy to be suspended by the turbulent action water or wind flow. | ||||
| biochemical sedimentary rocks | Sedimentary rocks formed from biologic processes; examples range from pieces of clam shells fused together into a solid mass to microscopic radiolaria fusing into chert | ||||
| biozone | An interval of geological strata that are defined on the basis of their characteristic fossil taxa. | ||||
| blind thrust fault | A thrust fault in which the surface exposure is obscured by fault movement | ||||
| blueschist | A rare metamorphic rock formed in subductionn zones under high pressure but low temperature, allowing the growth of distinctively-blue glaucophane; often called a glaucophane schist; found in metamorphosed former oceanic crust in the Franciscan Complex; notable California exposures include Ring Mountain, Tiburon. | ||||
| boiling pool | A type of hot spring that exhibits bubbling behavior | ||||
| boulder | A rock fragment greater than 256 mm in diameter | ||||
| braided fluvial environment | A river system comprised of multi-threaded channels that branch and merge to create the characteristic braided pattern. Braided channels are highly dynamic with mid-channel bars which are formed, consumed, and re-formed continuously. Such channels form on relatively steep slopes when compared ot meandering rivers, and have a higher capacity to move sediment in the bedload, suspended load, and disolved load of the stream. | ||||
| breakwater | A structure built parallel to the shore, some distance away from the shore, to effect a wave calming area between it and the beach | ||||
| breccia | Angular framents of rock. | ||||
| brittle Failure | Deformation by fracturing (discontinous deformation) | ||||
| caldera | A large hollow basin that forms from the evacuation of a magma chamber during a large volcanic eruption. | ||||
| cap rock | A layer of hard impervious rock overlying and often sealing in a deposit of oil, gas, or coal. | ||||
| carbon capture and sequestration | The process of capturing and storing atmospheric carbon dioxide. It is one method of reducing the amount of carbon dioxide in the atmosphere with the goal of reducing global climate change. | ||||
| carbonate | A mineral with the CO32- anion complex. | ||||
| carbonate reef | A coral reef is made of thin layers of calcium carbonate and/or magnesium carbonate. | ||||
| carbonatite | A type of intrusive or extrusive igneous rock defined by mineralogic composition consisting of greater than 50% carbonate minerals. | ||||
| Cascadia Subduction Zone | The location where the Juan de Fuca Plate suducts beneath the North American Plate; extends from Cape Menocio to Britsh Columbia. | ||||
| cataclasite | A fine grained, cohesive metamorphic rock, formed due to the local metamorphism in fault zones. | ||||
| chemical sedimentary rocks | Sedimentary rocks formed abiologically from chemical precipitates, often forming in hot water (e.g., geyserite formed from hot spring containing water saturated with dissolved silica) | ||||
| chert | A hard sedimentary rock formed from microcrystalline silica; in the California Franciscan context, chert is often biogenic in origin, deriving from the recrystallized remains of silica-shelled radiolaria, a single-celled organism that thrives in equatorial waters | ||||
| cinder cone | Volcano formed from the accumulation of scoria (cinders) around a single eruptive vent; steep conical hill with a prominent crater. | ||||
| cirque | A bowl-shaped, amphitheater-like depression that a glacier carves into a mountain or valley sidewall at high elevations. | ||||
| clast | An individual constituent, grain, or fragment of rock produced by the weathering of a larger rock mass. | ||||
| clastic | Pertaining to a rock or sediment composed of fragments derived from pre-existing rocksor minerals. | ||||
| Clear Lake volcanic field | A region north of San Francisco noted for its recent volcanic activity and current geothermal energy production. | ||||
| climate | A statistical pattern in long-term conditions of precipitation, temperature, etc. | ||||
| climate change | Long-term variations in climate; in the contemporary world, due to anthropogenic gases. | ||||
| climate forcing | An external factor exerting an influence on climate, such as orbital variation and changes in greenhouse gases. | ||||
| climate response | The complex and sometimes nonlinear reaction to climate forcing. | ||||
| coal | A black or dark brown rock composed of carbonized plant matter, often used as fuel due to it's combustibility. | ||||
| cobble | A fragment of rock greater than 64 mm and less than 256 mm in diameter. | ||||
| coeval | Having the same age or date of origin; rocks forming at the same time in different places. | ||||
| composite cone | An alternate term for composite volcano. | ||||
| composite volcano | A large volcanic edifice consisting of multiple vents formed over thousands or millions of years and composed of a variety of volcanic materials of a varitey of compositions. | ||||
| conchoidal fracture | A break along a curved surface which has the properties of a conchoid (a specific mathmatically defined curve), which resembles a scallop shell. | ||||
| continent-continent convergent boundary | A tectonic environment where two continents collide (e.g., the Indian Plate converging into the Eurasian plate) | ||||
| continental crust | Thicker, less dense crust which forms earth's continents and continental shelves. | ||||
| continental drift | A term now supplanted by the theory of plate tectonics describing relative movement of the crust of the Earth; Alfred Wegener first used the term continental drift (Kontinentalverschiebung). | ||||
| continental rift | A region within a continent where continental crust begins to thin and split apart. | ||||
| continental shelf | A portion of a continent that is submerged under an area of relatively shallow water. | ||||
| continental volcanic arc | A chain of volcanoes found on continental plate margins that are located along subduction zones. | ||||
| convergent boundary | A boundary where tectonic plates move toward each other. | ||||
| coral | A sedentary aquatic invertibrate which secretes a carbonate external skeleton; can also refer to the structure produced by the carbonate secretions, such as a coral reef. | ||||
| Coriolis effect | The phenomenon of warping/bending due to the rotation of the Earth | ||||
| country rock | The rock surrounding and igneous intrusion that was in place before the magma intruded. | ||||
| craton | An old and stable part of the continental lithosphere that is often at the core of a continent. | ||||
| crescent dune | Mounds of sand that are generally are wider than long and concave on the leeward side. | ||||
| cross bedding | Layering within a stratum and at an angle to the main bedding plane. | ||||
| dacite | An extrusive igneous rock with composition between feslsic and intermediate. | ||||
| dacitic | A rock with a composition similar to dacite. | ||||
| debris flow | Water-laden masses of soil and fragmented rock that are carried down mountainsides and funneled into stream channels. | ||||
| deflation | Lifting and removal of loose material from the surface by wind turbulence | ||||
| deformation | General process for folding, faulting, shearing, comrpession, or extension of rocks as a result of various natrual forces (such as confining pressure and temperature) | ||||
| delta | A landform shaped like a triangle, created by the deposition of sediment that is carried by a river and enters slower-moving or stagnant water. This occurs when a river enters an ocean, sea, estuary, lake, reservoir, or another river that cannot carry away the supplied sediment. | ||||
| dendrochronology | The study and dating of tree rings; particularly useful for climate studies. | ||||
| density | Mass per unit volume; a physical property calculated by the division of mass by volume; SI units are kg/m3 but usually expressed as g/cm3 | ||||
| desert pavement | A desert surface covered with closely packed, interlocking angular or rounded rock fragments of pebble and cobble size. | ||||
| desert varnish | Orange-yellow to black coating found on exposed rock surfaces in arid environments. | ||||
| detachment fault | Gently dipping normal faults associated with large scale extension; also referred to as “low angle normal faults” | ||||
| detrital sedimentary rock | see clastic sedimentary rock | ||||
| detritus | An individual constituent, grain, or fragment of rock produced by the weathering of a larger rock mass. | ||||
| diabase | a mafic igneous rock with a small but visible crystal size indicating medium cooling rates; diabase's crystal size falls between aphanitic (microscoping) basalt and phaneritic (easily visible) gabbro | ||||
| diamictite | a general term for a sedimentary rock consisting of nonsorted to poorly sorted terrigenous sediment. Particle sizes may range from clay to boulders, and are suspended within a matrix of mudstone or sandstone. | ||||
| diapir | a domed formation in which a core of rock or magma has moved upward to pierce the overlying strata. | ||||
| diatom | A microscopic, single-celled alga of the class Bacillariphyceae (ochrophytes), which lives in freshwater or marine environments. Diatoms secrete walls of silica, called fustules. Although diatoms are known from the Jurassic Perid, they first became abundant in the Cretaceous, ranging to the present. | ||||
| differential erosion | The unequal erosion occurring at shorelines, primarily due to wave refraction | ||||
| dike | 1) A sheetlike igneous intrusion that does not follow existing bedding structures; 2) A wall or embankment built to prevent flooding. | ||||
| dip | The angle that a planar feature makes with the horizontal, measured perpendicualr to the strike and in the vertical plane. | AGI | |||
| dip-slip fault | A fault on which the movement is parallel to the dip of the fault. | AGI | |||
| disconformity | A boundary between parallel layers of sedimentary rocks which represents a period of erosion or nondeposition | ||||
| divergent boundary | A boundary where tectonic plates move away from each other | ||||
| drainage basin | a region or area occupied by a drainage system, such as a river or stream | ||||
| drainage divide | a boundary between drainage basins | ||||
| dropstones | isolated rock fragments that are found within finer layers; often distorts the layers below as if dropped into soft sediment. | ||||
| ductile Failure | Visable solid-state deformation produces a change in the size and shape of a rock body without fracturing. Usually occurs where temperatures and pressures are high. | ||||
| earthquake | a motion or trembling of the Earth caused by the abrupt release of accumalated strain energy | ||||
| eclogite | A metamorphic rock consisting of pyroxene omphacite and pyrope-rich garnet. | ||||
| edifice | A building or structure; in geology: the structure of a volcano; usually a mountain or hill. | ||||
| effusive | In geology: nonexplosive ourpouring of lava. | ||||
| emergent shoreline | A shoreline in which processes of tectonic uplift and/or sea level drop exceed the tendency of fierce wave erosion to level shorelines; typical of California coasts | ||||
| eolian | Wind blown | ||||
| eon | The largest (formal) geochronologic time unit. | ||||
| epoch | The smallest geochronologic unit which subdivides Periods. | ||||
| era | The second largest geochronologic time unit. | ||||
| erosion | The removal or soil, rock and other material from an area. | ||||
| erratic | See glacial erratic. | ||||
| escarpment | a steep slope or long cliff that results from faulting. | ||||
| evaporite | Water-soluble sedimentary mineral deposit that results from concentration and crystallization by evaporation from an aqueous solution. | ||||
| exotic | Originating from far away. | ||||
| explosive | Able or likely to shatter violently or burst apart. | ||||
| extrusive | Erupted at the surface of the earth and cooled to solid above ground. | ||||
| fault | a boundary between two bodies of rock along which there has been relative motion. | ||||
| felsic | Low in iron and magnesium and high in silica. | ||||
| Field Act | California legislation involving restrictions in unreinforced masonry school buildings; enacted following the 1933 Long Beach quake | ||||
| fire fountain | A jet of lava sprayed into the air by the rapid formation and expansion of gas. | ||||
| flank | In the context of volcanoes: the slope of side of the volcanic edifice. | ||||
| flash floods | A rapid flooding of low-lying areas: washes, rivers, dry lakes and depressions. | ||||
| fluvial environment | A continental environment that is closely connected to the erosive and depositional activity of rivers, streams and are associated with gravity flow processes. | ||||
| flux melting | Melting that results when a chemical compound is added which lowers the melting temperature of the material. | ||||
| fold mountain range | Orogenic belt | ||||
| footwall | The footwall of a fault contains the rocks on the lower side of an inclined/tilted fault plane. | ||||
| forearc | The location between the suduction zone and the resulting magmatic arc. | ||||
| fractionation | Minerals crystallize and settle to the bottom of the magma chamber, leaving the remaining melt depleted of those ions. | ||||
| Franciscan Complex | a complicated, mutli-facted rock unit found in western California, typically made of metamorphosed sea floor rocks accreted onto North America | ||||
| fumerole | A vent in the surface of the Earth or another rocky planet from which hot volcanic gases and vapors are emitted, without any accompanying liquids or solids. | ||||
| fusulinid | An extinct order of single-celled organisms, which produced calcareous hard parts. | ||||
| gabbro | Mafic, intrusive igneous rock. | ||||
| gabbro | a mafic igneous rock with phaneritic (large, visible) crystals, indicating a slow coolilng rate | ||||
| Geographically Weighted Regression | A spatial analysis technique that takes non-stationary variables into consideration (e.g., climate; demographic factors; physical environment characteristics) and models the local relationships between these predictors and an outcome of interest. | ||||
| geosphere | The rocky part of planet Earth | ||||
| geothermal | Related to heat within the earth. | ||||
| ghost forest | a phenomenon associated with the 1700 Cascadia quake, where land dropped in such a way that living trees were inundated with salt water, killing them | ||||
| glacial erratic | Rocks that have been transported by ice and deposited elsewhere. | ||||
| glacial outwash | Sediment transported by the meltwater from a glacier. | ||||
| glaciation | A episode of relatively cold climate and glacial advance. | ||||
| glacier | A persistent body of dense ice, formed by the the accumulation and compaction of snow, which is constantly moving under its own weight. | ||||
| glass | A brittle, transparent or translucent noncystalline solid, usually consisting of silicates. | ||||
| Global Positioning System (GPS) | A global system of U.S. navigational satellites developed to provide precise positional and velocity data and global time synchronization for travel; it is widely used in earth sciences to measure ground motion. | ||||
| global warming | a problematic term that implies every place in the world is warming; climate change may, in fact, create some colder areas | ||||
| graben | Aa fault block, generally elongate, that has been lowered relative to the blocks on either side without major disturbance or pronounced tilting. | ||||
| graben | An elongate, depressed crustal unit or block bounded by faults on its long sides. | ||||
| granite | A plutonic rock which contains 10-50% quartz. | ||||
| granule | A rock fragment having a diameter in the range of 2-4 mm. | ||||
| greenhouse gasses | Gasses that easily absorb longwave radiation and contribute to the greenhouse effect. | ||||
| greywacke | a sedimentary rock with sandstone-range clasts often found in the Franciscan Complex, consisting of significant amount of clay and rock fragments, which indicate a relative immaturity of the rock | ||||
| groin | A structure built perpendicular to the beach, which acts to trap sand on one side and erode sand on the other | ||||
| groundmass | The majority of smaller mineral crystals that surround the larger phenocrysts in a porphyritic igneous rock. | ||||
| halide | A mineral whose anion is one of the halogen elements: chlorine, fluorine, bromine, etc. | ||||
| hanging wall | The hanging wall of a fault contains the rocks on the upper side of an inclined/tilted fault plane. | ||||
| hazard | A geologic process which may present a threat to human civilization. | ||||
| headland | A shoreline feature jutting out into the ocean | ||||
| high-grade | High-grade metamorphic rocks are formed by high temperatures and pressures and are characterized by the creation of new minerals. | ||||
| hinge | The locus of maximum curvature in a fold. | ||||
| horst | A type of valley and range topography created when the earth's crust is pulled apart. | ||||
| horst | An elongate, relatively uplifted crustal block that is bounded by faults on its long sides. | ||||
| hot spring | A location where geothermally heated groundwater emerges at the surface of the earth. | ||||
| hotspot | A volcanic center that persists for at least a few tens of millions of years that is thought to be the surface expression of a rising mantle plume. They are not associated with volcanic arcs. They may or may not be associated with oceanic ridges. | ||||
| hummock | A small knoll or mound above ground, typically less than 15 meters in height, which tend to appear in groups or fields. | ||||
| hummocky | An area with small knolls or mounds which may have been formed along a mass of ice. | ||||
| hydrocarbons | Compounds of hydrogen and carbon, such as those which are the chief components of petroleum and natural gas. | ||||
| hydrothermal | Related to hot water. | ||||
| igneous rock | Rock formed from the cooling and solidification of molten magma or lava. | ||||
| immature (sediment) | Asediment that s not uniform in appearance because the sediment grains are of varied sizes and shapes, and may have a large range of compositions | ||||
| index-fossil | The fossilized remains or traces of particular plants or animals that are characteristic of a particular span of geologic time or environment, and can be used to identify and date the containing rocks. | ||||
| inselberg | An isolated rock hill, knob, ridge, or small mountain that rises abruptly from a gently sloping or virtually level surface. | ||||
| instrusive | Cooled to solid within the earth. | ||||
| intensity | A measure of the effects of an earthquake at a particular place. It depends on the earthquake magnitude, distance from the epicenter, and local geology. | ||||
| intraplate | Within a tectonic plate | ||||
| island arc | A curved chain of islands rising from the deep ocean floor. | ||||
| isoclinal | denoting a fold of strata so acute that the two limbs are parallel. | ||||
| jetty | A structure built perpendicular to the beach, often in pairs protecting the mouths of rivers or harbors. | ||||
| joint | a boundary between two bodies of rock along which there has not been relative motion. | ||||
| Juan de Fuca Plate | A small tectonic plate consisting entirely of oceanic lithosphere formed at the Juan de Fuca Ridge and subducting beneath the North American Plate at the Cascadia Subduction Zone. | ||||
| Kerogen | A complex fossilized organic material, found in oil shale and other sedimentary rock, which is insoluble in common organic solvents and yields petroleum products on distillation. | ||||
| King Tides | an informal term for tidal phenomenon involving exceptional ranges of highs and lows; involves gravitational influence of moon and sun aligned with their elliptical orbits. | ||||
| lagoon | A body of water seperated from the sea by a sandbank or coral reef. | ||||
| lahar | An Indonesian term that describes a hot or cold mixture of water, volcanic ash, rock fragments, and other debris that flows down the slopes of a volcano and typically enters a river valley. | ||||
| land subsidence | a gradual settling or sudden sinking of the Earth's surface owing to subsurface movement of earth materials. Usually occurs due to fluid extraction, such as water or oil, in fine-grained materials. | ||||
| lava | Molten rock erupted from a volcano or vent above the surface of the earth. | ||||
| lava dome | See volcanic dome. | ||||
| lava tube | A natural conduit formed by flowing lava from a volcanic vent that moves beneath the hardened surface of a lava flow. | ||||
| left-lateral | a description of fault movement, where when one stands on one side of an offset fault and looks to the opposite side, the sense of offset is to one's left; this is a relative definition and does not indicate which side is actually moving. | ||||
| limb | The area of a fold between adjacent fold hinges. | ||||
| limestone | A sedimentary rock made chiefly of the mineral calcite. | ||||
| linear dune | Straight or slightly sinuous sand ridges typically much longer than they are wide. | ||||
| liquefaction | the phenomenon of loose, wet soil losing its strength when subjected to seismic movement | ||||
| lithic | Containing abundant fragments of previously formed rocks. | ||||
| lithosphere | The outermost layer of the solid earth based on mechanical properties, which deforms brittly; includes the crust a small part of the mantle. | ||||
| loess | Deposits of fine-grained wind-blown dust. | ||||
| longshore current | The movement of water parallel to a beach, generated by the zig-zag motion of wave swash and wave backwash | ||||
| longshore drift | The movement of sand parallel to a beach, driven by longshore currents | ||||
| low grade | Low-grade metamorphic rocks are formed at low temperatures and pressures and are not as altered. | ||||
| lower mantle | The part of the mantle below about 1,000 km in which the seismic velocity increases slowly with depth. | ||||
| mafic | Rich in iron and magnesium and low in silica. | ||||
| magma | Molten rock below the surface of the earth. | ||||
| magmatic differentiation | Separation of molten rock into distinct chemical compositions. | ||||
| magnitude | measure of the ground motion caused by an earthquake as measured on seismograms | ||||
| Mammuthus columbi | A columbian mammoth, an extinct animal closely related to modern elephants, prevalent in North America until the end of the last Ice Age; not to be confused with wooly mammoths, which lived at much higher latitudes than California; columbian mammoths had much longer tusks than modern elephants, as well as a distinct prominence the crest of their heads | ||||
| Mariana type subduction | Oceanic lithosphere subducts beneath oceanic lithosphere with an island arc and a back-arc spreading center. | ||||
| marine incursion | Flooding of a continent by the ocean. This could be due to sea level rise or tectonic subsidence. | ||||
| marine terraces | A series of former wave-cut platforms now exposed on land through a combination of tectonic uplift and/or sea level drop | ||||
| mass extinction | A short period of geologic time in which a large percentage of species become extinct (or die out). | ||||
| Mc | The minimum magnitude above which all earthquakes within a certain region are reliably recorded. | ||||
| Mediterranean climate | A climate pattern characterized by wet, temperate winters punctuated by long, dry summers | ||||
| megadrought | An informal term describing exceptionally dry conditions lasting over a period of many decades | ||||
| mélange | A mixture of rock types which lacks continuous bedding and contains rock fragments of all sizes; results from tectonic shearing forces, usually at convergent plate boundaries. | ||||
| Mendocino Triple Junction | the northern tectonic end of the San Andreas fault, where three plates (North American, Pacific, Juan de Fuca) meet in one spot; currently located offshore from Cape Mendocino | ||||
| Mercalli Intensity Scale | a scale to measure the damage caused by an earthquake from observing its effect on people, the environment, and Earth’s surface; reported as a Roman numerial from I to XII | ||||
| metamorphic core complex | exposures of deep crust exhumed in association with extension via low angle normal faults.. | ||||
| metasediments | A metamorphic rocks of sedimentary origin. | ||||
| mid-ocean ridge | A continuous mountain range extending through the North and South Atlantic Oceans, the Indian Ocean, and the South Pacific Ocean. It is the source of new crustal material. | ||||
| Milankovitch cycles | three orbital parameters (eccentricity, obliquity, precession), which in combination can exert climate forcing observable in the geologic record | ||||
| mineral | A naturally occuring, inorganic, crystalline solid with a defined chemical composition. | ||||
| miogeocline | Marine sedimentation along a passive margin. | ||||
| ML | The symbol for local magnitude. Local magnitudes are based on the maximum amplitude of the ground shaking, without distinguishing the different seismic waves. | ||||
| Moho | Informal name for the Mohorovičič discontinuity | ||||
| Mohorovičič discontinuity | The boundary between the crust and the mantle; the location within Earth where P-wave velocities abruptly change from a range of 6.7 to 7.2 km/s to greater than 7.6 to 8.1 km/s | ||||
| moment magnitude scale | A logarithmic scale to measure of the relative size of an earthquake based on ground motion, area ruptured, fault slip, and properties of the rock; now the standard way to report the magnitude of an earthquake | ||||
| monocline | A local steepening in an otherwise flat or shallowly dipping area. | ||||
| moraine | A mass of rocks and sediment carried and deposited by a glacier, typically as ridges at its edges or front. | ||||
| moraine | An accumulation of till in currently or formerly glaciated regions, typically forming a ridge. | ||||
| mud pot | A type of acidic hot spring that takes the form of a pool of bubbling mud as a result of the acid and microorganisms decomposing surrounding rock into clay and mud. | ||||
| mudstone | A sedimentary rock primarily composed of mud-sized clasts. It contains no laminations. | ||||
| Mw | The symbol for Moment Magnitude, a logarithmic scale to measure of the relative size of an earthquake based on ground motion, area ruptured, fault slip, and properties of the rock; now the standard way to report the magnitude of an earthquake | ||||
| mylonite | a foliated and often lineated rock with evidence for ductile deformation. | ||||
| native mineral | A mineral with only one element such as gold, copper, sulfur, or carbon. | ||||
| niche | The specific environmental condtions for which a species is adapted. | ||||
| nonconformity | A boundary between sedimentary rocks and metamorphic or igneous rocks when the sedimentary rock lies above and was deposited on the pre-existing and eroded metamorphic or igneous rock. | ||||
| normal fault | a dip-slip fault in which the block above the fault (the hanging wall) has moved downward relative to the block below (the footwall). | ||||
| normal fault | A fault in which the hanging wall has moved downward relative to the footwall. | ||||
| North American Plate | The tectonic plate that inlcudes most of North America and part of the Atlantic Ocean. | ||||
| North Pacific High | an area of long-lasting high atmospheric pressure that develops off the California coast and is responsible for diverting clouds and precipitation | ||||
| obduction | The process by which oceanic lithosphere is thrusted above or into continental lithosphere; not to be consfused with the common word, "abduction". | ||||
| oblique slip fault | A fault on which the slip is has components of both strike-slip and dip-slip. | ||||
| obsidian | A rock consisting of volcanic glass. | ||||
| ocean acidification | Increased carbon dioxide in the atmosphere dissolves in the ocean producing carbonic acid and decreasing ocean pH. | ||||
| ocean-continent convergent boundary | A convergent plate boundary where an oceanic plate and a continental plate are colliding. | ||||
| oceanic crust | The crustal rocks that underlie the ocean basins. | ||||
| oil reserves | An estimate of the amount of crude oil located in a particular economic region with the potential of being extracted. Reserves are calculated based on a proven probable basis and oil pools situated in unattainable depths are not considered part of a nation's reserves. | ||||
| Olenelloidea | Superfamily of trilobites, a group of extinct marine arthropods. | ||||
| olistostrome | A sedimentary deposit resulting from a submarine landslide. | ||||
| oncoids | A coated grain of algal (but not red algal) or microbial origin that is coarser than 2 mm in diameter. | ||||
| ophiolite | A terrane or part of a terrane that consists of oceanic lithosphere. | ||||
| orogenic belt | A region subjected to folding and other deformation during an orogenic cycle. | ||||
| orogeny | a mountain-building event | ||||
| orographic | Relating to mountains. | ||||
| orographic precipitation | the phenomenon of precipitation falling as clouds are forced to higher altitudes as they pass over mountains | ||||
| oxide | A mineral with oxygen as its anion. This excludes minerals with oxygen complexes such as carbonate, sulfate, or silicate. | ||||
| P wave | The type of seismic wave that involves alternating compression and expansion in the direction of propagation. | ||||
| Pacific plate | the largest of Earth's tectonic plates, spanning Asia to the west and California to the east | ||||
| paleoearthquake | Old earthquakes that have happened 1000's of years ago. | ||||
| paleoseismic | The study of past earthquakes using soil and rock records. | ||||
| palinspastic | a reconstruction of past tectonic movement that recreates the original position of rock units before they were displaced | ||||
| Pangea | A supercontinent existing from approximately 335 million years ago to 175 million years ago | ||||
| passive continental margin | The transition from continental crust to oceanic crust within a plate (as opposed to active margins which coincide with the edge of a plate. | ||||
| passive margin | The edge of a continent that does not experience tectonic activity (e.g. subduction, collision). | ||||
| pebble | A rock fragment having a diameter in the range of 2-4 mm. | ||||
| pediment | Very gently sloping inclined bedrock surface. | ||||
| peridotite | Ultramafic, intrusive igneous rock; the rock that makes up Earth's mantle. | ||||
| Period | A major rank below an Era and above an epoch. | ||||
| permeability | The state or quality of a material or membrane that causes it to allow liquids or gases to pass through it. | ||||
| Petroleum System | Encompasses a pod of active source rock and all genetically related oil and gas accumulations defined by the essential elements (source, reservoir, seal) and processes (generation-migration-accumulation). | ||||
| Petroleum System | A genetic relationship lining s source rock to all oil and gas it has genrated. It consists of all the geologic elements (carbon) and processes (heat, pressure and time) that re essential for the formation of a petroleum accumulation | ||||
| Phanerozoic | Phanerozoic means ‘visible life’ and is the current Eon on the geologic time scale having started 541 million years ago. | ||||
| phenocryst | A mineral crystal in a porphrytic igenous rock wich is larger than a surrounding groundmass of smaller mineral crystals. | ||||
| phosphate | A mineral with the PO44- anion complex. | ||||
| plagioclase feldspar | one of the major rock forming silicate minerals, consisting of a range of Na to Ca with a core of aluminium and silicate | ||||
| plankton | The small and microscopic organisms drifting or floating in the sea or fresh water, consisting chiefly of diatoms, protozoans, small crustaceans, and the eggs and larval stages of larger animals. | ||||
| plate boundary | Zone of seismic and tectonic activity along the edges of lithospheric plates. | ||||
| plate tectonics | the theory that the outer layers of Earth move relative to each other | ||||
| plateau | An region of high, flat topography. | ||||
| playa | A dry, vegetation-free, flat area at the lowest part of an undrained desert basin. | ||||
| plug dome | See volcanic dome. | ||||
| plunging fold | A fold in which the hing line is inclined (not horizontal). | ||||
| pluton | A body of intrusive igneous rock. | ||||
| plutonic | Of an intrusive igneous nature. | ||||
| porosity | The quality or degree of having minute spaces or holes through which liquid or air may pass. | ||||
| porphyritic | An ingneous texture in which some mineral grains, called phenocrysts, are much larger than the majority of the grains, called the groundmass. | ||||
| Prevailing Westerlies | Prevailing winds that blow from the west at midlatitudes. | ||||
| primary wave | The type of seismic wave that involves alternating compression and expansion in the direction of propagation. | ||||
| Principle of Baked Contacts | The principle stating that the heat of an intrusion will bake (metamorphose) the rocks in close proximity to the intrusion. | ||||
| Principle of Chilled Margins | A principle that states that the portion of an intrusion that has cooled and crystallized next to cold surrounding rock will form smaller crystals than the portion of the intrusion that cooled more slowly deeper in the intrusion, which will form larger crystals. | ||||
| Principle of Cross-cutting relationships | A principle of geology that states that the geologic feature which cuts another is the younger of the two features. | ||||
| Principle of Faunal Succession | A principle of geology that states that fossilized flora and fauna preserved in sedimentary rocks succeed each other vertically in a specific, reliable order that can be identified over wide horizontal distances. | ||||
| Principle of Inclusion | A geologic principle that states that clasts in a rock are older than the rock itself. | ||||
| Principle of Lateral Continuity | A principle of geology that states that layers of sediment initially extend laterally in all directions; in other words, they are laterally continuous | ||||
| Principle of Original Horizontality | A principle of geology that states that layers of sediment are originally deposited horizontally under the action of gravity | ||||
| Principle of Superposition | A principle of geology that states that in undeformed stratigraphic sequences, the oldest strata will lie at the bottom of the sequence, while newer material stacks upon the surface to form new deposits over time. | ||||
| pseudomorph | A mineral whose outward crystal form is that of another mineral; it is described as being "after" the mineral whose outward from it has, e.g. quartz after fluorite. | ||||
| pull-apart basin | a structural basin where two overlapping (en echelon) strike-slip faults or a fault bend creates an area of crustal extension undergoing tension, which causes the basin to sink down. | ||||
| pumice | A highly vesicular rock composed of volcanic glass. | ||||
| pyroclastic | A volcanic texture composed of fragments of a variety of volcanic materials. | ||||
| pyroclastic flow | A dense, destructive mass of very hot ash, lava fragments, and gases ejected explosively from a volcano and typically flowing downslope at great speed. | ||||
| quartzite | a hard, non-foliated metamorphic rock which was originally pure quartz sandstone. | ||||
| radiative forcing | the net balance of solar energy entering and exiting Earth; positive radiative forcing means that more energy is coming in than leaving, which is the current condition due to anthropogenic gases | ||||
| radioisotope | An isotope that has excess nuclear energy, usually due to the number of neutrons in its nucleus, making it unstable. | ||||
| radiolaria | a singled-celled marine organism which constructs a shell from silica extracted from sea water; radiolaria prefer warm, equatorial waters | ||||
| radiolarian chert | a silica-rich rock compared of recrystallized fossils of microscopic radiolaria | ||||
| radiometric dating | The fundamental method of geochronology. | ||||
| rain shadow | An area of significantly reduced rainfall behind a mountainous region, on the side facing away from prevailing winds, known as its leeward side. | ||||
| rare earth element | One of 17 metallic elements that include nclude the fifteen lanthanides on the periodic table plus scandium and yttrium | ||||
| reef | A ridge of jagged rock or coral near the surface of the ocean or other body of water. | ||||
| relative dating | A process by which the age of one geologic unit is determined relative to that of another. | ||||
| releasing bend | a curve in a strike-slip fault that creates areas of tension and normal faults; associated with land being lowered, sometimes resulting in sag ponds | ||||
| reservoir rock | In petroleum geology, any porous or permeable rock that yields oil or gas. Sandstone, limestone, and dolomite are common reservoir rocks, but in California, high-porosity, low permeability diatomite can also be a good reservoir rock. | ||||
| restraining bend | a curve in a strike-slip fault that creates areas of compression and reverse faults; associated with ridges and mountains being raised | ||||
| reverse fault | a fault in which the hanging wall moves up relative to the foot wall; this is a relative definition and does not specific which wall is actuall moving | ||||
| rhyolite | A felsic, extrusive igneous rock. | ||||
| rhyolitic | Of a composition similar to rhyolite. | ||||
| Ridiculously Resilient Ridge | a tongue-in-cheek term for exceptionally strong atmospheric pressure formations (see North Pacific High) | ||||
| right-lateral | a description of fault movement, where when one stands on one side of an offset fault and looks to the opposite side, the sense of offset is to one's right; this is a relative definition and does not indicate which side is actually moving; many major faults in California, such as the San Andreas, Calaveras, and Hayward, are right-lateral faults | ||||
| rip current | The phenomenon of water moving swiftly away from the beach, perpendicular to the beach, in a narrow flow; a common cause of drowning | ||||
| rip-rap | An anti-erosion construction composed of large boulders | ||||
| Rivera Triple Junction | the southern tectonic end of the San Andreas fault, where three plates (North American, Pacific, Cocos) meet in one spot; currently located offshore south of Baja California | ||||
| rock gypsum | A chemical sedimentary rock that forms from evaporation. It is composed of many crystals of the mineral gypsum. | ||||
| rock salt | A chemical sedimentary rock that forms from evaporation. It is composed of many crystals of the mineral halite. | ||||
| Rodinia | A supercontinent that incorporated almost all the landmasses on Earth for about 450 million years during the Proterozoic Eon (2.5 billion to 541 million years ago). | ||||
| roof pendant | A mass of country rock that projects downward into and is entirely surrounded by an igneous intrusion such as a batholith or pluton. | ||||
| roundness | The degree of abrasion of a clastic particle. | ||||
| runoff | The draining away of water (or substances carried in it) from the surface of an area of land, a building or structure, etc. | ||||
| salinity | concentration of dissolved solids (salts) in a solution. | ||||
| saltation | A means of particle transport by fluids such as wind or water that occurs when loose materials are removed from a bed and carried by the fluid, before being transported back to the surface. | ||||
| sand | A clast smaller than a granule (pebble) and larger than a silt grain, with a diameter of 1/16 to 2 mm. | ||||
| sand ramps | An accumulations of sand sized sediment along the front of mountain ranges. | ||||
| sand sheets | Flat or gently undulating sandy deposits with only small surface ripples | ||||
| sandstone | A clastic sedimentary rock composed of grains of sand size. | ||||
| scoria | A mafic rock with vesicular texture in which more than 50% of the rock is composed of vesicles. | ||||
| sea arch | A semi-curved cut in the rock of a headland, formed by wave refraction creating differential erosion on the sides of the headland | ||||
| sea caves | An indentation in a headland or a rocky coast created by wave erosion | ||||
| sea stack | A remnant of a former headland, now disconnected from the mainland, isolated through differential erosion | ||||
| sea-floor spreading | The movement of ocean crust away from one another at 1-10 mm per year. | ||||
| seal rock | A rock whose petrophysical properties, mainly low permeability, make it capable of impeding the upward migration of oil or gas. | ||||
| seawall | A structure built on land, parallel to the beach, intended to take the impact of waves and forestall wave erosion | ||||
| secondary wave (S-wave) | a seismic shear wave where the particle motion is perpendicular, or at right angles, to the direction of wave propagation | ||||
| sedimentary basin | A circular downfolded structure that has been filled with sediment and contains sedimentary rocks. | ||||
| seismic moment | a measure of the size of an earthquake based upon properties of the rock, the area ruptured when a fault breaks, and the slip or displacement caused by the fault | ||||
| seismic wave | a general term for energy waves caused by earthquakes, explosions, or machines used to artifically generate energy waves | ||||
| seismogram | a recording of data from the arrival of earthquake waves or seismic waves | ||||
| seismograph | a device that records data from the arrival of earthquake waves or seismic waves; seismographs have largely been replaced by computers directly recording data digitally | ||||
| seismologist | a person who studies earthquakes or the movement of seismic wave energy | ||||
| seismology | the study of earthquakes or of the movement of seismic wave energy | ||||
| seismometer | a device to detect data from the arrival of earthquake waves or seismic wave energy; the data detected are now usually recorded on computers, but used to be recorded on seismographs | ||||
| serpentine soil | Soil that develops where serpentinite or similar rocks are the dominant parent material; rich in heavy-metals relative to other elements. | ||||
| serpentinite | a metamorphosed ultramafic rock which often presents in a variety of green colors, and has much lower density than its parent rock; serpentinite contains small amounts of chrysotile asbestos, in addition to minerals such as lizardite and antigorite; serpentinite is frequently weakk and easily fractured, making hills underlain by serpentinite particularly vulneralbe to landslides; serpentinite is the rock name, while serpentine is an adjective; California's official state rock | ||||
| shale | A fine-grained clastic sedimentary rock, formed by the compaction of clay, silt, or mud. It is finly laminated. | ||||
| shield volcano | A large volcanic edifice consisting of multiple vents formed over thousands or millions of years and composed mainly of basalt and having a broad, flat profile. | ||||
| silica | A chemical compound of silicon and oxygen. | ||||
| silicate | A compound whose crystal structure contains SiO4 tetrahedra. | ||||
| sill | A sheetlike igneous intrusion that intrudes between existing stratigraphic layers. | ||||
| siltstone | a clastic sedimentary rock made mostly of silt and fine mud. | ||||
| slab window | A gap in a subducted plate that forms when a spreading ridge intersects a trench. | ||||
| slickenfibers | Linear mineral growths on a fault surface, formed during movement of the fault. | ||||
| slickenlines | Linear striations on a smooth fault surface, formed by the movment of the fault. | ||||
| slip rate | The average speed of the relative motion between footwall and hanging wall within a specified period | ||||
| Smilodon californicus | an extinct Pleistocene predatory large cat, found in great numbers in California's La Brea Tar Pits | ||||
| Smilodon fatalis | an extinct Pleistocene predatory large cat, found in great numbers in California's La Brea Tar Pits | ||||
| snow water equivalent | the amount of water if a column of snow was melted instantaneously | ||||
| soft-first story | a seismically vulnerable building design with the street-level floor open and with few supports, commonly designed this way to accommodate parking or retail space | ||||
| sorting | The process by which particles are naturally separated from dissimilar particles by the agents of transportation. | ||||
| source rock | Sedimentary rock in which organic material under pressure, heat, and time was transformed into liquid or gaseous hydrocarbons. Source rock is usually shale or limestone. | ||||
| speleothems | A structure formed in a cave by the precipitation of minerals from water; examples include stalactites and stalagmites. | ||||
| spheroidal weathering | A form of chemical alteration that affects jointed bedrock and results in the formation of concentric or spherical layers of highly decayed rock. | ||||
| spreading center | A linear zone in the seafloor, typically found along a mid-ocean ridge, along which magma rises and from which adjacent crustal plates are moving apart. | ||||
| spreading center | a tectonic area where two plates grow away from each other, with a volcanic line in between; also called a divergent tectonic boundary | ||||
| Steam Injection (Enhanced Oil Recovery) | technology for producing heavy crude oil and bitumen. High pressure steam is continuously injected into the oil resrvoir to heat the oil and reduce its viscosity, causing the heated oil to mobilize and move to where it is pumped out. | ||||
| stoss | The side of a dune or rounded feature that faces toward the source of a current | ||||
| stratigraphic unit | A body of rock of similar rock type and similar charateristics formed within the same time range. | ||||
| stratovolcano | An alternate term for composite volcano. | ||||
| strike | The compass direction of a plane as it intersects a horizontal plane. | ||||
| strike slip fault | Strike-slip faults involve motion which is parallel to the strike of the fault--frequently described as a "side-by-side" motion. | ||||
| Stromatoperoid | An extinct clade of sea sponges common in the fossil record from the Middle Ordovician to the Late Devonian.[1] They can be characterized by their densely layered calcite skeletons lacking spicules. | ||||
| subduction | The process of oceanic crust moving beneath another tectonic plate and into the mantle | ||||
| sufate | A mineral with the SO42- anion. | ||||
| suflide | A mineral with the S2- anion. | ||||
| supercontinent | The assembly of most or all of Earth's continental blocks or cratons to form a single large landmass. | ||||
| suspended load | The portion of sediment carried by a fluid turbulence (water or air) uplifted by the fluid's flow in the process of sediment transportation.Generally consists of smaller particles, like clay, silt, and fine sands. | ||||
| synclinal Trough | A linear depression or basin that subsides as it receives clastic material, located not far form the source supplying the sediment. | ||||
| syncline | A fold which the core contains the stratigraphically younger rocks; it is generally concave upward. | ||||
| syncline | A fold of which the core contains the stratigraphically younger rock. It is generally concave upward. | ||||
| synform | A fold whose limbs dip inward and for which the ages of the rocks are unknown. | ||||
| tephra | All pieces of all fragments of rock ejected into the air by an erupting volcano. | ||||
| terrain | An area of land considered in relation to its topography and surface features, especially as they relate to overland travel. | ||||
| terrane | A fault-bounded area or region with a distinctive stratigraphy, structure, and geological history. | ||||
| terrigenous | derived from land, as opposed to the ocean (marine). | ||||
| thermal expansion | the change in size of objects depending on temperature | ||||
| thin section | A slab of rock ground thin enough for light to pass through it, which is used to study rocks under a microscope. | ||||
| thrust fault | a reverse fault (where the hanging wall moves up relative to the foot wall, commonly because of tectonic compression) with a very low angle | ||||
| till | Glacial sediment. | ||||
| tombolo | An island or sea stack that has reconnected to land via a sand spit deposited by the wave calming effects of the island or sea stack | ||||
| Trade Winds | East-to-west prevailing winds that flow in the Earth's equatorial region. T | ||||
| transform boundary | A plate boundary where plates slide past each other without new lithosphere being created, or old lithosphere being destroyed | ||||
| transpression | A type of deformation that includes both pure shear (compression) and simple shear (shearing). | ||||
| transpression | a tectonic condition where side-to-side movement also includes a percentage of compression; a tectonic change favoring transpression in the last few million years is a major reason for the promiment mountains and ridges found in the California Coast Ranges | ||||
| transtension | A type of deformation that includes both extension and simple shear (shearing). | ||||
| transtension | a tectonic condition where side-to-side movement also includes a percentage of expansion | ||||
| transverse dune | A large, strongly asymmetrical, elongated dune lying at right angles to the prevailing wind direction. | ||||
| trench | a tectonic feature of lowered crust associated with subduction; a California example is the | ||||
| Trilobite | Extinct marine arthropod | ||||
| triple junction | The point where three tectonic plates meet. | ||||
| tsunami | Giant waves produced through tectonic action, volcanic eruption, or meteorite strike into the ocean | ||||
| tufa | A form of microcrystalline limestone. | ||||
| tuff | A volcaniclastic igneous rock. | ||||
| Turbidite | Sediments transported and deposited by density flow generally tends to gradually change from coarse-grained at the base to fine-grained at the top of the sedimentary sequence and that was deposited by turbidity currents. | ||||
| turbidity flows | a submarine movement of sediment downsope, depositing as a rock known as turbidite, a distinctive sedimentary deposit composed of alternatiing layers of clay and sand-sized clasts, often forming in repeated bands where the lower part of the band has larger grains that fine upwards to smaller grains | ||||
| u-shaped valley | A valley with steep walls that curve into a reltively flat bottom, rembling the letter 'U' in profile; usually the result of glacial erosion. | ||||
| ultamafic | very rich in iron and magnesium and low in silica. | ||||
| ultramafic | The chemistry of the mantle; even richer in iron and magnesium (and lower in silica) than mafic rocks. | ||||
| unconformity | A buried erosional or non-depositional surface separating two rock masses or strata of different ages, indicating that sediment deposition was not continuous. | ||||
| upwelling | The phenomenon of deep, cold, nutrient-rich water rising to the surface waters because of the effects of wind direction and the Coriolis effect | ||||
| vent | In the context of volcanoes: an opening in a volcanic edifice from which lava or pyroclastic material erupts. | ||||
| ventifact | A rock that has been abraded, pitted, etched, grooved, or polished by wind-driven sand or ice crystals. | ||||
| vesicle | A hole produced by a bubble of gas when the lava cools around the bubble. | ||||
| vesicular | Having many vesicles | ||||
| viscosity | The state of being thick, sticky, and semifluid in consistency, due to internal friction. In short, the resistance for a fluid to flow. | ||||
| volcanic arc | A chain of volcanoes formed as a result of subduction, including volcanic island arcs as well as volcanic arc mountain ranges. | ||||
| volcanic arc mountain range | A chain of volcanoes formed on a continent as a result of oceanic lithosphere subducting beneath contientnal lithosphere. | ||||
| volcanic butte | An isolated hill or mountain resulting from the differential weathering or erosion and consequent exposure of a volcanic neck, or a of a narrow veritcal igneous instrusion overlying weaker rock | ||||
| volcanic dome | A steep-sided, rounded accumulation of lava extruded from a volcano to form a dome-shaped or bulbous mass of congealed laval above and aorund the vent. Commonly parasitic on the flanks of, or within the crater of, larger edifices | ||||
| volcanic island arc | A chain of volcanic islands formed when one plate of oceanic crust subducts beneath another plate of oceanic crust | ||||
| volcano | A structure such as a hill or mountain which forms around an individual vent or multiple vents from which lava or pyroclastic material emerges. | ||||
| Walker Lane | A geologic trough roughly aligned with the California/Nevada border southward to where Death Valley intersects the Garlock Fault, a major left lateral, or sinistral, strike-slip fault. | ||||
| wave amplitude | The height of a wave compared to the theoretical ocean level if no waves were present | ||||
| wave backwash | The movement of waves down a beach face, back into the ocean | ||||
| wave period | The time in seconds between successive waves | ||||
| wave refraction | The warping and bending of waves due to “feeling bottom” in different places along the wavefront | ||||
| wave swash | The movement of waves up a beach face | ||||
| wave-cut platform | A flat submerged area subjected to breaking waves, often immediately between sandy beaches and deeper waters | ||||
| wavelength | The distance in meters between two crests of two waves | ||||
| waves “feeling bottom” | The phenomenon of waves interacting with the ocean bottom when the oncoming wave reaches depths less than one-half of the wavelength | ||||
| weather | a short-term atmospheric event at a particular time in a particular place | ||||
| Western Interior Seaway | The Western Interior Seaway [1] was a huge inland sea. It split North America into two halves for most of the mid- and late-Cretaceous Period. It was up to 2,500 feet (760 m) deep, 600 miles (970 km) wide and over 2,000 miles (3,200 km) long. | ||||
| wildcatting | Wildcatting is a term used in the oil industry, where companies drill test wells for oil in unexplored or wild areas. | ||||
| Wilson cycle | The cycle of continental rifting, the formation of a new ocean basin as rifting advances, followed by the closure of the ocean basin as plates collide | ||||
| xenolith | A fragment of rock within a body of igneous rock that is different from the surrounding rock; originating as country rock that became incorporated into a body of magma without melting and assimilating. |