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Creating Realistic Terrain
Creating realistic terrain involves more than simply sculpting out a feature
and plonking it on the landscape. To truly create a believable landscape, the
process of natural desert formation has to be understood, so that deserts can
be created in believable locations.
Defining a desert
A desert is defined as places where almost nothing lives. They are known as
deserts, because they are deserted.
Deserts are driven by the weather. The flow of water on the landscape around
the desert is what defines the size and shape of any desert. This means that
surrounding landscape has to be taken into consideration, as does the weather.
Hot deserts exist in warm locations, usually at or near the tropics. They
are covered in sand, rock, or small stones. The land is often good quality,
except it is bereft of water, which is what makes the hot desert so dangerous.
Hot deserts do not have to be rolling sand dunes, and can be flat and rocky
just as easily. These deserts are typically extremely hot during the day,
offering little or no shade, yet plummeting quickly in temperature at night.
These conditions: rapid heating and cooling, are extreme enough to break rocks.
Cold deserts are actually covered in water. The problem is, this water is
all frozen, way below zero centigrade - life cannot exist in frozen water.
Cold deserts are typically where the air is very cold, at the caps of a world,
or the tops of high mountain ranges.
Sometimes deserts form around active volcanoes. Ash not only fills the lungs
of most animals, choking them, and blocks sunlight, but the fine ash particles
will bond with water in the air, dropping it as acidic rain. If an eruption
is ongoing, a small desert will form in the ash shadow, a desert that is normal
temperature, covered in extremely fertile ash, but completely bereft of water.
A fourth type of desert is the poison desert. These crop up when the landscape
is filled with a substance poisonous to life. No matter how much water there
is, if it is mixed with poison, nothing will live there, and a desert will
form. The dead sea is an example of such, where a sea filled with water has
such a high salt content, that absolutely nothing can live there. Other poison
deserts include salt flats, and even ocean deserts, where effluent has mixed
with the seawater, killing off everything that grows along the current's path.
The formation of Deserts
Deserts form when there is either not enough water for anything to grow, or
the water that is available is unusable due to temperature, acidity, or other
toxins. Whatever the reason, the main contributing factors are water and wind.
Rain Shadow Desert
Water does not sit still. If a world has weather, it has moving water, continually
circulating. Water evaporates from any standing body, and flows through the
air into greater and greater clouds, rising and rising until it meets colder
air, at which point it rapidly condenses and falls as rain. If the clouds
rise too high, the water freezes and snow forms. The height of the land forces
clouds higher, which is why it snows over mountains.
If the prevailing wind is blowing east, then water collected from bodies
of water to the west will evaporate into clouds, and rise over land heading
east. Some will fall back as rain, some will survive to reach the mountains,
and most will deposit on the western slopes of those mountains. The wind will
flow over the mountains, but the last of the moisture will have frozen and
fallen as snow or sleet. It will hardly ever rain on the eastern slopes, or
the lands to the east of the mountains - thus, a rain shadow desert will form.
Distant Sea Desert
Most of the larger deserts hot are a long distance from any major body of
water such as a lake or sea. Any moisture picked up on the wind, is rained
back to earth long before it reaches the desert land, so the desert stays
hot and dry.
Near Sea Desert
Paradoxically, a desert can be found near a large body of water. This occurs
when the prevailing wind direction moves across the desert first, then over
the water. Any water evaporating into the air from the sea, meets a warm land
breeze and condenses into mist. No water is left for rain, so a desert stretches
As you can see, the common feature in desert formation is always water and
wind. Not enough water, or water blown to high so it freezes, or pollutants
blown into the path of the water, or water raining on stretches of toxic material
wikl create a desert. The lesson to remember is the surrounding landscape and
the weather patterns your world will have, determine the formation of deserts,
not the other way round.
The weather itself transforms the appearance of hot deserts. When rain does
fall, it falls in short, fierce storms which wash away all top layers of soil
and sand, exposing the bare rock beneath. Later wind storms whip up the remaining
sand, blasting it across the rock, eroding it at speed. Very little is more
abrasive than fast-moving sand.
Canyons are formed in some deserts. They occur where hills have had their
edges and soft soil eroded away by the blowing sand, which works in from the
sides far more than the top; eventually leaving misshapen pillars of rock
where the core of the hill once was. Softer rock wears away faster, sometimes
leaving holes or canyons.