ALLUVIAL FAN - A fan-shaped sloping deposit of alluvium, whose source is usually a canyon from an adjacent mountain range, located at the head of the fan.
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ALLUVIAL FAN - A fan-shaped sloping deposit of alluvium, whose source is usually a canyon from an adjacent mountain range, located at the head of the fan. |
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ALTIPLANO - High arid plateau or tableland of South America.
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ARCH - An erosional remnant in sedimentary rock, in a stable, arch-shape, rising above the basal rock layers, as opposed to a "Natural Bridge". |
ARID - This term is defined in the dictionary as a region which receives too little water to support agriculture without irrigation. Less than ten inches of rainfall a year could be considered "arid." Some desert regions receive much less - their total average rainfall can be measured in tenths of an inch.
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ARROYO - (Box Canyon) - A deeply notched canyon, usually in hard sedimentary layers, with steep, unclimbable walls, and no way out except the downstream entrance |
Here in this typical California "Arroyo," the walls are not so steep as to be completely inclimbable. Some arroyos in the Colorado Plateau area are completely unscalable without technical equipment. |
ARTESIAN SPRING - An actively flowing spring, where the water table is higher than the containing topography.
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BADLANDS - A region characterized by poor soil development, sparse vegetation, and characteristically-eroded clay and silt layers, sometimes assuming fantastic shapes. |
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BAJADA -
BOX CANYON - A deeply notched canyon, usually in hard sedimentary layers, with steep, unclimbable walls, and no way out except the downstream entrance. (Arroyo)
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BUTTE - A tall, steeply-walled, isolated erosional construct, with a smaller summit area compared with a mesa, (generally higher than wide). |
CANYON - A deep gully, caused by extensive persistent fluvial erosion.
DESERT DEPRESSION - In many arid regions there are localities, called "Depressions," that are considerably lower in elevation than the surroundings. Structural in origin, these localities can be lower than median sea level. At first, it might seem peculiar that these areas occur only in desert regions. But such structures are likely to be filled in through more active sedimentation in less arid regions, or possibly flooded by the ocean. Examples are: the Quattara Depression and the Danikil Depression in Africa, Death Valley and the Imperial Valley in North America, the Dead Sea region on the Arabian Peninsula, the Caspian Sea in western Asia, and the Turfan Depression in western China. There are others, but all those mentioned have basal elevations below sea level.
DESERT PAVEMENT - See "Pediment".
DRY LAKE (Playa or Pan) - A lake bed, where the water accumulates, but later evaporates or goes underground. Usually a flat, featureless brownish-gray clay will form, or possibly salt deposits, as exposed surface layers, when the water has retreated.
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DRY VALLEYS (Antarctica) - Cold desert microclimes. These are true desert regions despite their frigid average daytime temperatures. For more on these unusual places visit this site. The polar regions, as with the tropics, receive little precipitation, because these are areas where the weather is dominated by cool, descending air. |
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DUNE - A construct of unconsolidated, wind-blown sand, often temporary, and frequently non-stationary. |
KOPPIES - Small hills or hillocks, possibly in groups. ("Kopje" - an Afrikanner term.)
MALPAIS (Or "Malapai") - Much the same as "badlands," but more volcanic in origin, with the rock formations the result of primary rock-forming episode such as lava flows, rather than by subsequent erosion.
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MESA - An erosional construct with steeply-sloping to vertical sides and a large flat top. Similar to a butte, but a larger ratio of top to side surface areas. |
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NATURAL BRIDGE - A naturally-occurring, horizontal undercut remnant in sedimentary rock.
PAN - See Dry Lake.
PEDIMENT - Much the same as "Desert Pavement". A flat surface, covered with interlocked, but loosely cemented pebbles. Pediments are common in areas subject to wind scouring, removing sand and silt, and leaving behind pebble-sized and larger stones.
PLAYA - See Dry Lake.
SALT LAKE or SALAR - A desert lake, where, in the cycle of water influx and subsequent evaporation, the salty minerals are brought along and left behind, causing the lake to become increasingly salty. (Often well beyond the oceans in terms of salinity.) The Great Salt Lake in Utah is a good example.
SINK - A lake, where the piezometric surface is below ground level. Water flowing into the often marshy areas seems to just disappear into the ground.
SPRING - A point where the water table is above a usually sloping land surface, with the result of water being expelled from the ground. A source for surface water from the ground.
TANKS - A pond or catchment of potable water, often in a desert region, and thus of significance to those living in the region. A water hole.
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WASH - A narrow, constricting channel in a desert, usually dry, but subject to partial or complete inundation during a flash flood. |
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ABRASION - A physical erosion process, where solid particles are moved across a solid surface (with the help of wind or water), resulting in the removal of mass form the surface
CORRASION - Physical erosion - not chemical.
DEPOSITION - The laying down of solid material originally suspended or otherwise transported by wind or water.
DESSICATION - In arid regions, the tendency for evaporation can be so severe that water-containing objects, such as animals and plants, can lose their moisture as well. This process is called dessication.
DUST DEVIL - A small cyclonic wind, which often picks up dust and silt particles form the desert floor
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DUST STORM - In arid regions, strong surface winds can pick up and suspend much soil that consists of silt or smaller particles. When this happens, the event is called a "Dust Storm" in the American Southwest. |
ECOLOGY - This is the science of how plants and animals of a given region inter-relate with each other.
EROSION - The removal of solid material through a physical or chemical process.
EVAPORATION - The phase change of water from a liquid to a gaseous state. This requires energy, such as sunlight.
FLASH FLOOD - A brief rush of water through a valley or canyon following a heavy downpour of rain in an otherwise arid region.
KHAMSIN - A hot southerly wind of Egypt.
MIRAGE - An optical illusion created by hot air rising from the ground, refracting the light of the sky, giving the appearance of water to an observer some distance away.
MICROCLIMATE - Most of the time, the term "desert" arbitrarily refers to a region with a definite boundary. But in fact, this boundary may be very difficult to define, and the climatic specifics may vary greatly of the entire region in terms of temperature ranges and the presence of water. This can be particularly true near the boundaries of some other temperate, tropical or other kind of non-desert region, and in certain areas we refer to as desert, there may be a great deal of water available. For example, the riparian ecological communities near the Colorado River have profoundly different plant and animal life from the true desert climate that exists just a short distance away. Grasses may dominate near the river, but succulents have their sway just a mile or so away. This is just one example of microclimate differences. High versus low desert is another - in this case the transition may be more gradual.
NICHE - In an ecological sense, this word refers to a role, or a way in which a certain plant or animal fits in with the rest of its overall local community of thiving things.
SIROCCO (or Scirocco) - A hot or otherwise oppressive wind, frequently dust-laden, associated with the northern Sahara or southern Mediterranean region.
ZEPHYR - A big wind, possibly associated with a dust storm.
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