Area Of Critical Environmental Concern (ACEC). An area within public lands where special management attention is required to protect and prevent irreparable damage to important historic, cultural or scenic values, fish and wildlife resources, or other natural systems or processes, or to protect life and safety from natural hazards. (FLPMA, Section 103(a)).

Other Articles: Wild Horse Canyon Road: 36000 Eastern Mojave Geology: 220000  

Other Articles: Glossary: bajada inselberg  

alluvial fan. A gently sloping (ten degrees or less) fan shaped deposit of sediments formed where an intermittent stream undergoes an abrupt reduction in slope. Coarsest materials are found near the apex of the fan (nearest the mountain or hill front) whereas the finest materials occur farthest from the mountain front.

alluvium. Material, including sand, clay, gravel, and mud, deposited in river beds, lakes, alluvial fans, valleys, and elsewhere by modern streams.

amphibolite. A crystalloblastic rock consisting mainly of amphibole and plagioclase with little or no quartz. As the content of quartz increases, the rock grades into hornblende-plagioclase gneiss.

amphibolite facies. The set of metamorphic mineral assemblages in which basic rocks are represented by hornblende + plagioclase, the latter being oligoclase-andesine or a more calcic variety, The facies is typical of regional metamorphism under moderate to high pressures and temperatures.

Other Articles: Blackbrush: 406500 Glossary: entomophilous  

anemophilous Pollinated by wind. See also: entomophilous.

Animal Unit Month (AUM). A unit of measure of the impact of a grazing animals on range land. An AUM is equivalent to the amount of forage required by a 1,000 pound cow for 1 month (BLM, 1980, p. 68). A calf might give an AUM value, sheep another, etc..

Literature Cited:
- Biness, Naomi L., and Mark D. Zoback, 2006.  

Locations: San Andreas Fault Zone.  

Boness and Zoback (2006) present shear velocity anisotropy data from local earthquake sources as an independent tool to analyze the state of stress close to active faults on a regional scale.

anthropology. the science that deals with the origins, physical and cultural development, racial characteristics and social customs and beliefs of mankind.

Other Articles: Glossary: syncline  

anticline. A configuration of folded, stratified rocks in which the rocks dip or incline in two directions away from the crest, like the two halves of a pitched roof. The reverse of a "syncline".

arid. Zero to ten inches precipitation per year. Potential for evaporation exceeds annual precipitation.

ash. 1. Inorganic residue remaining after ignition of combustible substances, quantitatively determined by definite prescribed methods. 2. Volcanic dust and particles less than 4 mm. in diameter.

ash, volcanic. Uncemented pyroclastic material consisting of fragments mostly under 4 mm. in diameter. Without a qualifying adjective, the term should be applied only to essential ejecta.

ash fall. 1. A rain of airborne volcanic ash falling from an eruption cloud. Characteristic of vulcanian eruptions. 2. A deposit of volcanic ash resulting from such a fall and lying on the ground surface. (AGI)

ash flow. 1. An avalanche of volcanic ash, generally a highly heated mixture of volcanic gases and ash, traveling down the flanks of a volcano or along the surface of the ground and produced by the explosive disintegration of viscous lava in a volcanic crater or by the explosive emission of gas charged ash from a fissure or group of fissures. Ash flows of the type described at Mount Pelee are considered to represent the feeblest type of the nuee ardente. The solid materials contained in a typical ash flow are generally unsorted and ordinarily include volcanic dust, pumice, scoria, and blocks in addition to ash. 2. A deposit of volcanic ash and other debris resulting from such a flow and lying on the ground surface. Syn: ignimbrite. (AGI)

ash flow tuff. A tuff resulting from an ash flow.

Other Articles: Glossary: welded_tuff  

Aso lava. A type of indurated pyroclastic deposit produced during the explosive eruptions that formed the Aso Caldera of Kyushu, Japan. Chiefly a lavalike tuff consisting of lenses or spindles of black and gray obsidian lying in a tuffaceous matrix that displays a streaky, varicolored banding or eutaxitic structure. Possibly erupted as extremely hot, gas rich dust and ash carrying large clots of molten, vesiculated volcanic glass. Similar to deposits variously described as welded tuff, welded pumice, ignimbrite, and tuff-lava. (AGI)

Other Articles: Eastern Mojave Geology: 149000  

aulacogen. A long lived deeply subsiding trough, at times fault bounded, that extends at high angles from a geosyncline far into an adjacent foreland platform.

Other Articles: Glossary: synecology Vegetation of the Mid Hills: 62800  

autecology n. Study of the requirements, tolerances, and responses of a single organism (Oosting 1956:12). The ecology of a species or of individual organisms in relation to the environment (Webster).

avalanche, volcanic. Avalanche usually refers to a large mass of ice and snow, sometimes accompanied by other material, moving rapidly down a mountain slope. A volcanic avalanche is a general term relating to movement of large masses of volcanic material, ususally tephra, moving rapidly down a mountain slope without regard for temperature and gas content.

axiolite, axiolitic. No definition in AGI, 1962. Defined in Ross and Smith, 1961.

Other Articles: Glossary: alluvial_fan  

bajada. 1. The slope or continuous apron comprised of merged alluvial fans. 2. A series of merged alluvial fans along the base of a mountain range.

Literature Cited:
- American Geological Institute, 1960.

Other Articles: Glossary: roof_pendant  

batholith 1. Originally defined in 1895 as a stock-shaped or shieldshaped mass of igneous rock intruded as the fusion of older formations. On removal of its rock cover and on continued denudation, this mass holds its diameter or grows broader to unknown depths. 2. A body of intrusive rock, with the general characteristics of stocks, but of much larger size than is generally attributed to stocks or bosses.

bench. A strip of relatively level earth or rock, raised and narrow. A small terrace or comparatively level platform breaking the continuity of a declivity (AGI).

block. An angular fragment over 256 mm. in diameter showing little or no modification in form due to transportation; similar in size to a boulder. (AGI, 1962).

blueschist. At high pressure and low temperature, albite feldspar breaks down and forms the pyroxene jadeite and amphiboles like glaucophane and aegerine. The amphiboles are bluish, hence the term "blueschist."

High pressures (5 to over 8 kb) and low to moderate temperatures of 250° to 600° C (480° to 1,100° F) form blueschist facies. Blueschist facies is typical of subduction-zone metamorphism as tectonic plates fold over one another.

bolson. In arid regions, a basin filled with alluvium and intermittent lakes and having no surface water outlet.

Other Articles: Wild Horse Canyon Road: 36000 56000 Eastern Mojave Geology: 220000 Columbia Mine  

Other Articles: Eastern Mojave Geology: Unable to find an article page.  

Bryozoa. Phylum of tiny colonial animals equipped with a circle or loop or tentacles surrounding the mouth that build calcareous structures of many kinds, mostly marine. Ordovician to Recent. The phylum of invertebrate animals which are popularly called "moss animals". (Called Polyzoa by some zoologists.)

capture. See stream capture.

carbonate bank. A submarine plateau composed of limestone, much like the present-day Bahamas.

carbonate mineral. Mineral formed by the combination of the complex ion (CO3)2- with a positive ion. Common example: CaCO3, calcium carbonate, the primary constituent of limestone.

Other Articles: Swertia albomarginata: 100200  

California Desert Conservation Area (CDCA). The 25 million acre CDCA contains over 12 million acres of public lands administered by the BLM. The boundaries are formed by the Nevada border and Colorado River on the east. The United States / Mexico boundary forms the southern boundary. Western boundaries are mostly desert areas on the east sides of the Peninsular Ranges, the Transverse Ranges, the Tehachapi Mountains and the Sierra Nevada.

Other Articles: Kelbaker Road: 16000  

cinder cone. A type of volcano which is built exclusively or in large part of pyroclastic ejecta dominated by cinders (particles 0.01 to 1 inch in diameter). Seldom exceeds 1,500 feet in height. Slopes up to 30 or 40 degrees.

Other Articles: Eastern Mojave Climate: Climate  

Other Articles: Eastern Mojave Geology: 173000  

craton. A relatively immobile part of the earth, generally of large size.

Other Articles: Eastern Mojave Geology: 172300  

crinoid. an echinoderm of the class Crinoidea, having a cup-shaped body to which are attached branched, radiating arms, comprising the sea lilies, feather stars, and various fossil forms.

crystalline. The orderly arrangement of atoms in a crystal. Rock which is made up of crystals. Examples: igneous and metamorphic rocks.

crystallization. The process of forming crystals by cooling a molten substance.

Other Articles: Field Notes: 19-Apr-08 Eastern Mojave Geology: 380000  

desert pavement. A residual deposit produced by continued removal of clay and dust by wind which leaves a surface covered with close packed pebbles. 2) Such as desert pavement. Desert crust. When loose material containing pebbles or larger stones is exposed to wind action the finer dust and sand are blown away and the pebbles gradually accumulate on the surface, forming a sort of mosaic which protects the finer material underneath from attack. This is the desert pavement. Synonym: pebble mosaic (AGI). See discussion in Chapter XI -- Geomorphology.

diamictite. A sedimentary rock consisting of poorly sorted, noncalcareous, terrigenous sedimentary rock (e.g., pebbly mudstone) containing a wide range of particle sizes. It has been suggested that the diamictites of the Pahrump Group are suggestive of glacier ice-rafted material.

dune. A low hill, or bank, of drifted sand (AGI).

Literature Cited:
- Best. Myron G., 1982.
- Coleman, R. G., D. E. Lee, L. B. Beatty, and W. W. Brannock., 1965.    

eclogites (Coleman and others, 1965) are essentially bimineralic rocks comprised of almandine-pyrope garnet and jadeite-diopside pyroxene but with a bulk chemical composition essentially the same as that of basalt. Their relatively high density (3.4 to 3.5 g/cm³) suggests formation under high pressure and probably dry conditions (Best, 1982).

eclogite. A granular rock composed essentially of garnet (almandine-pyrope) and sodic pyroxene (omphacite). Rutile, kyanite, and quartz are typically present. (AGI, 1984)

Literature Cited:
- Bjørnerud, M. G., and H Austrheim., 2004. Eclogite P-T Pathways

Other Articles: Eastern Mojave Geology: 140200  

eclogite facies. The set of metamorphic mineral assemblages (facies) in which basic rocks are represented by omphacitic pyroxene and almandine-pyrope garnet. Phase-equilibrium work has shown that these high-density mineral associations indicate a high pressure of crystallization.

edaphic adj. Of or relating to soil, esp. as it affects living organisms (Webster). Pertaining to, or influenced by, soil conditions (Munz 1965).

endemic adj. 1. Prevalent in or peculiar to a particular locality or people. 2. Ecol. Native or limited to a certain region (Webster).

Other Articles: Blackbrush: 406530  

entemophily. n. The state of relying upon insects for pollination.

Other Articles: Glossary: anemophilous  

entomophilous adj. Pollinated by insects.

ephemeral pool. A pool of water which contains water only during the wet seasons. Drys up completely at some time during the seasons.

ethnography. a branch of anthropology dealing with the scientific description of individual cultures.

Other Articles: Glossary: welded_tuff  

eutaxite, eutaxitic. Applied to a structure of certain volcanic rocks with a streaked or blotched appearance due to the alternation of bands or elongated lenses of different color, composition or texture; the bands, etc., having been originally ejected as individual portions of magma which were drawn out together in a viscous state and formed a heterogeneous mass by welding. The term is most appropriately used in describing the structure of a majority of welded tuffs. (AGI)

fan. An accumulation of debris brought down by a stream descending through a steep ravine and debouching in the plain beneath, where the detrital material spreads out in the shape of a fan, forming a section of a vary low cone (AGI).

fault. A surface of rock rupture along which there has been differential movement. A fracture in rock in which the two blocks on either side have moved in respect to each other.

fault block mountains. A mountain bounded by one or more faults. When two faults bound a mountain they may be responsible for the movements which have uplifted the block which was eroded to form a mountain.

fold. A bend, flexure, or wrinkle in rock produced when the rock was in a plastic state.

fossil. any remains, impression, or trace of an animal or plant of a former geological age, as a skeleton, footprint, etc.

Other Articles: Glossary: maquis  

strong>garrigue

Overgrazing and exploitation of the maquis shrub community reduces it to an open vegetation of low, small shrubs (eg species of Satureja, Euphorbia and Thymus and including most of those of the maquis), many bulbs and annual species. This community, garrigue, is a mass of flowers in the spring, but they soon go over to become parched and dusty, with the annuals and above-ground parts of the bulbous plants dead and crisp. Joan Head Editor, The Lavender Bag

Other Articles: Swertia albomarginata: 100600  

Other Articles: Black Canyon Road: in Round Valley New York Mountain Road.: 23000 Wild Horse Canyon Road: 36000 Eastern Mojave Geology: 220000 Columbia Mine  

granite. A coarse-grained igneous rock dominated bt light-colored minerals with minor amounts of dark-colored minerals. Quartz and feldspar dominate. Makes up about 95% of all intrusive igneous rocks found on the continents.

granulite. 1. A metamorphic rock consisting of even-sized, interlocking mineral grains. 2. A coarse granular metamorphic rock of the granulite facies.

granulite facies. The metamorphic facies in which basic rocks are represented by diopside + hypersthene + plagioclase. It is typical of deep-seated regional dynamothermal metamorphism, at temperatures in excess of 650°C.

greenschist. A schistose metamorphic rock whose green color is due to the presence of chlorite, epidote, or actinolite.

greenschist facies. The metamorphic facies in which basic rocks are represented by albite + epidote + chlorite + actinolite. It includes the common products of low-grade regional metamorphism, and is believed to correspond to temperatures in the range 300°-500°C.

Other Articles: Swertia albomarginata: 100200  

hornfels A fine-grained rock composed of a mosaic of equidimensional grains without preferred orientation and typically formed by contact metamorphism. Porphyroblasts or relict phemochrists may be present in the characteristically granoblastic matrix.

hornfels facies. A loosely defined term used to denote the physical conditions involved, or the set of mineral assemblages produced, by thermal (contact) metamorphism at relatively shallow depths in the earth's crust (AGI).

Other Articles: Interstate 15: near Devil Peak

Locations: Devil Peak.  

igneous rock. An aggregate on interlocking silicate formed by the cooling and solidification of a natural silicate melt.

Other Articles: Glossary: welded_tuff Eastern Mojave Geology: 420300  

ignimbrite. 1. A silicic volcanic rock forming thick, massive, compact, lavalike sheets that cover a wide area in the central part of North Island, New Zealand. The rock is chiefly a fine grained rhyolitic tuff formed mainly of glass particles (shards) in which crystals of feldspar, quartz, and occasionally hypersthene or hornblende are embedded. The glass particles are firmly "welded" and bend around the crystals, and evidently were of a viscous nature when they were deposited. The deposits are believed to have been produced by the eruption of dense clouds of incandescent volcanic glass in a semimolten or viscous state from groups of fissures. Syn: welded tuff. 2. The deposit of a fiery cloud or pyroclastic flow, extensive and generally thick with well developed prismatic jointing.

indurated. Rendered hard; confined in geological use to masses hardened by heat, baked, etc., as distinguished from hard or compact in natural structure. In modern usage the term is applied to rocks hardened not only by heat, but also by pressure and cementation.

Other Articles: Glossary: alluvial_fan  

inselberg. A lone, resistant, steep sided hill or mountain, formerly part of a larger mountain range, that is surrounded by alluvial fan or playa deposits.

intrusive rock. A rock that solidified from a mass of once molton material that invaded the earth's crust but did not reach the surface.

Other Articles: Glossary: polycarpic semelparous  

iteroparous (Latin "again" "birth") Refers to plants that have repeated periods of reproduction. See also: polycarpic.
Antonym: semelparous, monocarpic.

lacustrine. 1. Produced by or belonging to lakes. 2. Of, or pertaining to, or formed or growing in, or inhabiting, lakes.

lahar. 1. Landslide or mudflow of pyroclastic material on the flank of a volcano. 2. Deposit produced by such a landslide. May be wet or dry, hot or cold.

lapilli. Essential, accessory, and accidental volcanic ejecta ranging mostly from 4 mm. to 32 mm. in diameter.

Literature Cited:
- American Geological Institute, 1983.
- Reynolds, Robert E., 2001.
- Reynolds, Robert E., 2006.
- Wyatt, Anthony., 1992.. Liesegang weathering in the Silurian Hills.

Other Articles: Field Notes: 20010422100 at Field Trip Stop 1-3 Glossary: spheroidalw

Locations: Silurian Hills.  

Liesegang Weathering. 1. Secondary, nested rings or bands caused by rhythmic precepitation within a fluid saturated rock (AGI, 1983). 2. A small-scale, more or less concentric, chemical reaction effect, seen as discrete, but largely contiguous, structures throughout a part of a rock body. Each structure shows, on an exposed surface, ring-shaped bands of concentric colour. The effect is probably caused by rhythmic precipitation in a gel (a jelly-like colloidal solution), perhaps a kind of weathering process........… (Wyatt, 1992).

lithification. The process by which unconsolidated rock-forming materials are converted into a consolidated or coherent state, i.e., turned into a rock.

Other Articles: Glossary: garrigue  

maquis

If fires in the evergreen forest are too frequent to allow natural regeneration of the trees, or man removes them for timber, then degraded vegetation of low shrubs (2 – 4m high) occurs. This is called maquis and is usually dominated by Cistus spp., Pistacia lentiscus, Rosmarinus officinalis, Juniperus spp., lavenders, Arbutus and other ericaceous plants.Joan Head Editor, The Lavender Bag

Literature Cited:
- Barbour, Michael G., Jack H. Burk, and Wanna Pitts, 1987.    

mast year. A year in which an iteroparous woody perennial reproduces heavily, followed by one or more years of little or no reproduction. Mast years are common in temperate trees and serve to increase the chances of seeds escaping granivores. Mast years may be unpredictable when the reproductive cycle responds to external rather than physiological changes. Alternatively, irregular reproduction may be caused by severe resource depletion during the mast year. The period of time necessary to replace the energy reserves is often unpredictable because it varies with environmental conditions. Predictable mast years are found in conifers where the reproductive process takes a predictable time to complete (Barbour, et al., 1987)

mesa. A table land; a flat topped mountain or other elevation bounded on at least one side by a steep cliff; a plateau terminating on one or more sides in a steep cliff (AGI).

metamorphic rock. "Changed-form rock", any rock that has been changed in texture or composition by heat, pressure, or chemically active fluids after its original formation. Conditions of formation usually found miles below the earth's surface, thousands of atmospheres of pressure, cloe to the melting point.

mineral. A naturally occurring solid element or compound. It is inorganic, has a definite composition, or ranges within definite limits. It has an orderly internal atomic structure and may express this in the form of visible crystals.

Other Articles: Glossary: polycarpic semelparous Swertia albomarginata: 100700  

Other Articles: Field Notes: 26-May-04 Nevada Highway 265: near the Monocline  

monocline

1. A fold in layered rock that creates a slight bend.
2. Double flexure connecting strata at one level with same strata at another level.
3. single upward band or fold.

mudflow, volcanic. See "lahar".

nuee ardente. See ash flow.

Other Articles: California Highway 120: at Nunatak Nature Trail Field Notes: 1-Aug-07 at Nunatak Nature Trail  

nunatak. A nunatak is an isolated knob or peak of bedrock that projects prominently above the surface of a glacier and is surrounded by glacier ice. The word is derived from the Eskimo for "lonely peak."

palynology. The study of pollen and other spores and their dispersal, and applications thereof.

patina. A thin, light colored, outer layer produced by wind action and weathering.

Literature Cited:
- Strudley, Mark W., A. Brad Murray, and P. K. Haff, 2006.

Other Articles: Eastern Mojave Geology: about pediments  

pediment. A sloping rock surface forming a ramp up to the front of a mountain range in an arid region. It may be covered by thin alluvium.

pediplain. A widely extending, dominantly gentle sloping or rolling surface which is rock cut and alluviated.

pelean eruption. Designating or pertaining to a type of volcanic eruption characterized by explosions of extreme violence and the formation of nuees ardentes, or ash flows. The lavas involved in this type of eruption are generally extremely silicic and viscous.

Other Articles: Swertia albomarginata: 100200  

Other Articles: Black Canyon Road: Woods Mtns Petroglyphs Wild Horse Canyon Road: 60000  

phenology n. Study of periodic biological phenomena, as breeding, flowering, and migration, esp. as related to climate (Webster).

Other Articles: Wild Horse Canyon Road: 60000  

plain. A region of general uniform slope, comparatively level, of considerable extent, and not broken by marked elevations and depressions; it may be an extensive valley floor or a plateau summit. Any extent of level or nearly level land (AGI).

playa. 1. The flat floor of a bolson in an arid region. It is underlain by silts, clays, and complex associations of different salts. 2. The shallow central basin of a desert plain, in which water gathers after a rain and is evaporated (AGI).

playa lake. An intermittent lake which occupies the flat floor of a bolson.

Other Articles: Glossary: iteroparous monocarpic  

polycarpic. Refers to plants that have repeated periods of reproduction. Synonym: iteroparous. Antonym: monocarpic.

prehnite-pumpellyite. The characteristic assemblages of this facies are developed only from fine-grained unstable starting materials such as glassy volcanic rocks, pyroclastics and greywackes. Diagnostic minerals may also occur in veins cutting largely unrecrystallized rocks.

pumice. An excessively cellular glassy lava, generally of the composition of rhyolite.

pyroclastic. A general term applied to detrital volcanic material that have been explosively or aerially ejected from a volcanic vent. Also a general term for the class of rocks made up of these materials.

pyroclastic rock. Fragmental rock blown out by volcanic explosion and deposited from the air. Rocks formed from bombs, blocks, cinders, ash, tuff, and pumice.

refugia. As used in ecology, refers to small areas, or even microclimates, where a species can survive when it could not do so in the surrounding area.

relict n. An organism or species of an earlier era surviving in an environment which has changed considerably (Webster). A localized plant left over from an earlier geological period (Munz 1965).

rock. An aggregate of minerals of different types which may be in varying proportions. Contrast with "mineral".

Literature Cited:
- American Geological Institute, 1960. Mt. Tom, 12 miles west of Bishop, Inyuo County, California

Other Articles: Glossary: batholith U. S. Highway 395: 50200

Locations: Mount Tom.  

roof pendant. Older rocks projecting down from the roof into a batholith. On a map the roof pendant is completely surrounded by the rocks of the batholith

Other Articles: Swertia albomarginata: 100300  

salina. A saline playa, that is mostly underlain by complex associations of different salts.

Other Articles: Field Notes: 2-Aug-08 at Navy Beach

Locations: Navy Beach.  

sand tufa. Sand tufa is formed when fresh water springs percolate through the sandy lake bed of an alkaline lake. Contact with the alkaline salts cause calcium carbonate in the fresh water to precipitate in the sand. If the lake level drops, the uncemented sand can be eroded away, either by water or wind, leaving the sand tufa behind.

scoria. Volcanic slag. Pyroclastic ejecta, usually of basic composition, characterized by marked vesicularity, dark color, heaviness, and a texture that is partly glassy and partly crystalline. Fragments of scoria between 4 mm. and 32 mm. are essentially equivalent to volcanic cinders.

sediment. The loose fragments of minerals and rocks which are transported by the wind, rivers, and glaciers as well as currents in lakes and the ocean.

Other Articles: Glossary: iteroparous monocarpic Swertia albomarginata: 100700  

shale. a laminated sediment in which the constituent particles are predominantly of the clay grade.

Literature Cited:
- American Geological Institute, 1983. Unusual deep weathering pattern.

Other Articles: Caruthers Canyon Road: 30500 Glossary: liesegang  

spheroidal weathering. A form of chemical weathering in which concentric shells of decayed rock (ranging in size from 2 cm to 2 m) are successively loosened and separated from a block of rock by water penetrating the bounding joints of other fractures and atttacking the block from all sides. It is similar to the larger-scale exfoliation produced usually by mechanical weathering. Syn: onion-skin weathering; concentric weathering; spherical weathering (AGI, 1983) Different from Liesegang Rings.

Other Articles: Eastern Mojave Geology: Unable to find an article page.  

stratification. The structure produced by the deposition of sediments in layers or beds. May be found in pyroclastic and sedimentary rocks.

stream capture. The diversion of the upper part of a stream by the headward growth of another stream. Also called beheading, piracy, and stream robbery.

Other Articles: Field Notes: 19-Apr-08  

supergene. Applied to ores or ore minerals that have been formed by generally descending water. Ores or minerals formed by downward enrichment.

Other Articles: Glossary: anticline  

syncline. A configuration of folded, stratified rock in which the rocks dip downward from opposite directions to come together in a trough. The reverse of an "anticline".

Other Articles: Glossary: autecology Vegetation of the Mid Hills: 62800  

synecology n. study of groups of organisms, often in a natural setting (Oosting 1956:12). The study of the environmental interrelationships among communities of organisms (Webster).

Other Articles: Wild Horse Canyon Road: 60000  

tafoni. Cavernous weathering features which have arch-shaped entrances, convex walls, overhanging upper margins, and fairly smooth, gently sloping floors.

talus. A collection of fallen disintegrated material which has formed a slope at the foot of a steeper declivity. Synonym: scree (AGI).

tephra. A collective term for all clastic volcanic materials which during an eruption are ejected from a crater or from some other type of vent and transported through the air; includes volcanic dust, ash, cinders, lapilli, scoria, pumice, bombs, and blocks. Syn: volcanic ejecta. (AGI)

terrace. Benches and terraces are relatively flat, horizontal, or gently inclined surfaces, sometimes long and narrow, which are bounded by a steeper ascending slope on one side and by a steeper descending slope on the opposite side. Both forms, when typically developed, are step like in character (AGI). Benches are smaller than terraces. An example of a terrace can be found in lower Opal Wash, while benches are found on the west side of Wild Horse Canyon, north of the Ceremonial Site.

topographic. Of or pertaining to the forms found at the earth's surface. The configuration of the earth's surface as it forms valleys, ridges, peaks, etc.

tuff. A rock formed of compacted volcanic fragments, generally smaller than 4 mm. in diameter.

turtleback. Large smoothly curved topographic surface underlain by folded metamorphic rocks in the Death Valley region; resembles a structural nose with amplitude up to several thousand feet.

turtleback fault. Low angle fault which has brought Cenozoic sedimentary and volcanic rocks into contact with metamorphics at a turtleback surface; interpreted as a folded overthrust or as a plane along which normal faulting or extensive landsliding has occurred.

Vertical Angle Bench Mark (VABM). A marked point of known elevation, established through survey of vertical angles (????).

volcanic ash. See "ash, volcanic".

volcano. Landform developed by the accumulation of cooled molten rock products near a central vent of opening.

wash. A watercourse, usually dry, with a loose surface of sand, gravel, boulders, etc..

watercourse. A natural channel for water.

Other Articles: Eastern Mojave Climate: 31200  

weather. The state of the atmosphere at a given time and place, described by specification of variables such as terperature, moisture, wind velocity and barometric pressure.

Other Articles: Wild Horse Canyon Road: Lobo Point 60000 Glossary: Aso_lava eutaxite ignimbrite Eastern Mojave Geology: 340000 669500  

welded tuff. A tuff which has been indurated by the combined action of heat retained by the particles and the enveloping hot gases.

Other Articles: Swertia albomarginata: 100500  

Literature Cited:
- Lackey, Jade Star, and John W. Valley, 2004.

Other Articles: U. S. Highway 395: at Laurel Mtn

Locations: Laurel Mountain.  

yardang. Irregular ridges, commonly alternating with round-bottomed troughs, formed by eolian erosion.

zeolite. A generic term for a large group of hydrous aluminosilicates that are analogous in composition to the feldspars; have a ratio of (Al + Si) to nonhydrous oxygen of 1:2; and are characterized by their easy and reversible loss of water of hydration and by their ready fusion and swelling when strongly heated. Zeolites have long been known to occur as well-formed crystals in cavities in basalt. Of more significance is their occurrence as authigenic minerals, especially in beds of tuff.

Literature Cited

Location records referred to by this literature:

• San Andreas Fault Zone, Riverside County, California.

Location records referred to by this literature:

• Laurel Mountain, Mono County, California.

Location records referred to by this literature:

• Eastern Star Wash, San Bernardino County, California.
• Silurian Hills, San Bernardino County, California.

Location records referred to by this literature:

• Sacaton Mountains, Pinal County, Arizona.
• Joshua Tree National Park, Riverside County, California.
• Cima Dome, San Bernardino County, California.

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Date and time this article was prepared: 5/8/2008 9:42:13 AM