1. Most noted for desert conditions
Rub’al Khali in Arabian Desert
Most of Saudi Arabia is unsuitable for humans
World‘’s largest uninterrupted area of sand
Rubʿ al-Khali, ( Arabic: “Empty Quarter”) also spelled Al-Rabʿ al-Khali,  vast desert in the southern Arabian Peninsula, covering about 250,000 square miles (650,000 square km) in a structural basin lying mainly in southeastern Saudi Arabia, with lesser portions in Yemen, Oman, and the United Arab Emirates. It is the largest area of continuous sand in the world. It occupies more than one-quarter of Saudi Arabia. The topography is varied. In the west the elevation is as high as 2,000 feet (610 metres) and the sand is fine and soft, while in the east the elevation drops to 600 feet (183 metres) with sand dunes, salt flats, and sand sheets. One of the driest regions in the world, it is virtually uninhabited and largely unexplored. However, in 1948 Al-Ghawār, the world’s largest oilfield, was discovered there. For convenience, several townlike names were given to different locations along the field
The sparsely populated Karakum Desert occupies about 80 to 90% of the total area of the Republic of Turkmenistan. Not surprisingly sandstorms and dust storms are very common in the country. The karakum possesses  large reserves of  oil, natural gas, and the third largest deposits of sulphur in the world. Compared to other deserts it has limited but adequate rainfall for ephemeral vegetation growth, a factor that allows for nomadic pastoralism. Moreover, ample irrigation water, allowing even  the growing of Cotton, is provided by the Murghab and Hari rivers flowing into the desert, as well as by the soviet constructed Karakum Canal,  the largest irrigation canal in the world which connects the Amu Darya River with the Caspian sea. Seepage from the Karakum canal has led to the creation of numerous lakes and ponds along its course, a source of natural beauty but also increasing salinization due to rising  groundwater levels.
Average air temperatures range from 26 to 34 °C in summer, and −4 °C to 4 °C  in winter, however extreme seasonal fluctuations are common with ranges from −20 °C in winter to +50°C in summer, and day temperatures may differ sharply between daylight and nighttime.
The Karakum Desert, also spelled Kara-Kum and Gara-Gum (Turkmen: Garagum, pronounced [ɡaɾaˈɡum]; Russian: Караку́мы, tr. Karakumy; IPA: [kərɐˈkumɨ]; Kazakh: Қарақұм), is a desert in Central Asia. Its name means Black Sand in Turkic languages. It occupies about 70 percent, or 350,000 km², of the area of Turkmenistan.
The population is sparse, with an average of one person per 6.5 km² (one person per 2.5 square miles). Rainfall is also sparse, ranging from 70 to 150 mm.[1]
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 [Location[edit]
Covering much of present-day Turkmenistan, the Karakum Desert lies east of the Caspian Sea, with the Aral Sea to the north and the Amu Darya river and the Kyzyl Kum desert to the northeast. In modern times, with the shrinking of the Aral Sea, the extended "Aral Karakum" has appeared on the former seabed, with an estimated area of 15,440 sq mi/40,000 km². Although the level of the Aral Sea has fluctuated over its existence, the most recent level drop was caused by the former Soviet Union building massive irrigation projects in the region. Although the North Aral Sea is currently rising, the South Aral Sea is still dropping, thus expanding the size of the desert.[2]
The sands of the Aral Karakum are made up of a salt-marsh consisting of finely-dispersed evaporites and remnants of alkaline mineral deposits, washed into the basin from irrigated fields. The dust blown on a full east-west airstream carry pesticide residues that have been found in the blood of penguins in Antarctica. Aral dust has also been found in the glaciers of Greenland, the forests of Norway and the fields of Russia
Karakum Desert
The Karakum Desert covers 135,000 square miles -- nearly 70 percent of Turkmenistan. Because of the desert's location along the Caspian Sea, the weather in Karakum is milder than many Asian deserts, which typically experience frigid winters and scorching summers. Average summer temperatures remain below 100 degrees Fahrenheit, while winters typically hover around freezing. The Aral Karakum is a separate, unconnected desert within the confines of Kazakhstan.
Kyzylkum Desert
Crossing over Kazakhstan into Uzbekistan, the 115,000 square mile Kyzylkum Desert features a wide variety of flora and fauna. Though the area only receives 4 to 8 inches of rain per year, the rain occurs during the region's cooler period so the water does not dissipate quickly and supports large migratory game such as deer, boar and antelope as well as turtles, lizards and birds. The region's rich fauna dates back to prehistoric times, as documented over a series of archeological digs that have uncovered a wealth of dinosaurs and early mammals.
Kyzylkum is of the world’s largest deserts, and  visitors can trek its red sand on foot or on their very own Silk Road camel.
Named after its red sand, it is the 11th-largest desert in the world and spreads across northern Uzbekistan and up into neighbouring Kazakhstan. From March to May and September to October, you can trek on foot or by camel from the village of Yangi Kazgan, just north of Lake Aidarkul, and camel treks of two days or more include accommodation in the camel hair yurts belonging to local Kazakh nomads. Expect to enjoy the best of local hospitality, from homemade bread dipped in still steaming camel milk to hunks of camel meat. Beds are made up on the floor from piles of rainbow-coloured blankets and rugs, and you’ll often sleep cheek-by-jowl with other guests. You’ll never forget the experience, and certainly won’t get cold at night. You can arrange camel trekking through agents in Nurata or, alternatively, approach the camel camps directly. The two companies that dominate the market, both of which provide a high level of service, are Sputnik Camel Camp (Tel: ; and the nearby Yangi Kazgan Yurt Camp (Tel: ). In each of these cases you’ll pay US$45–50 per person per day for accommodation, meals and a camel trek. Don’t expect to get too fond of your mount – camels are surprisingly hard creatures to love when you get up close and personal. Wet wipes will undoubtedly come in handy
- See more at:
The Kara Kum (Turkmenistan) and Kyzyl Kum (Uzbekistan

2. The Sahara is the world’s largest hot desert
Largest dry region in the world
Less than 10 inches of rain a year
The sahara is 3.5 million square miles
Because the desert air contains little moisture or humidity, few clouds form over dry land
This raises temps (125 degrees F)
At night it can be 40 degrees F
About the size of the US
In the Gobero Area of the Sahara Desert in Niger, a 6,000 year old "Tenerian" skeleton was found with his middle finger in his mouth for reasons that are unknown. The average daily high temperature in this part of the Sahara Desert was 120F degrees (49C), a far cry from the Green Sahara 4-9,000 years ago. (© Mike Hettwer)
The Sahara is the world’s largest desert. At over 9,000,000 square kilometers (3,500,000 sq mi), it covers most of Northern Africa, making it almost as large as the United States or the continent of Europe. The desert stretches from the Red Sea, including parts of the Mediterranean coasts, to the outskirts of the Atlantic Ocean. To the south, it is delimited by the Sahel: a belt of semi-arid tropical savanna that comprises the northern region of central and western Sub-Saharan Africa.

3. These deserts often have:
“ergs” (seas of sand)
“dunes” (mounds of sand)
“regs” (desert pavement/gravel)
“hamadas” (sandstone plateaus)
Grand Erg Occidental
Grand Erg Oriental
Erg Chech
ERGS:  When most people think about deserts, they usually think of sand dunes, which are called ergs.   Ergs cover about 20 percent of the Sahara and can stretch for hundreds of miles at heights of up to 1,000 feet.  Formed in depressions [low spots]ergs, can also contain large quantities of salt from dried-up ancient lakes.   For thousands of years, that salt has been traded across the Sahara.  [see photo right]  
REGS:  Regs are large flat areas covered with a layer of sand and gravel [small rocks].  Regs make up 70 percent of the Sahara.  The regs are where prehistoric seas and rivers used to be.  The regs are now nearly completely waterless.  Because regs are so dry, there is little plant life.   The animal life is limited to insects, a few lizards and small rodents.
HAMADAS:  In the desert there are large, elevated plateaus of rock and stone.   In the Sahara, those areas are called "hamadas."   They can be over 11,000 feet high.   Some examples of hamadas include the Atlas Mountains in southern Morocco and western Algeria; Tassili N'Ajjer massif in southeastern Algeria (up to 7,800 ft.); Tibesti Mountains of southern Libya and northern Chad (up to 11,204 ft.); the Ahaggar Mountains (9,852 feet), [they were formed by a volcanic explosion] in the center of the Sahara.   The Sahara's highest point is the summit of Mount Koussi in the Tibesti Mountains. (11,204 ft.)
WADIS:
Shesh is how “Chech” sounds
Occidental means West
Oriental means East
Dune---A mound or ridge of sand or other loose sediment formed by the wind, esp. on the sea coast or in a desert: "a sand dune".
They are stationary and never move but a few feet in a year
A violent wind storm could move them 60 feet in a day though….dust storms that cover things with sand like lava does from a Volcano
An erg (also sand sea or dune sea, or sand sheet if it lacks dunes) is a broad, flat area of desert covered with wind-swept sand with little or no vegetative cover
Erg Chech, sandy region of the Sahara in western Algeria and northern Mali. It consists largely of shifting dunes.

4. Additionally, “wadis” are found after heavy rainfall
Temporary pools or rivers of water
Another interesting fact about Saudi Arabia is that it has no permanent rivers or lakes. Though you can find wadis(water wells) in the rainy season. Vegetation is very sparse and few animals live in this arid region.

5. An “oasis” is also occasionally found
Natural springs of fresh water found in deserts
Some may be small ---like a cluster of trees or small town
Other oasis are large enough to maintain an entire city
The Sahara has 90 of these
An oasis is an area made fertile by a source of freshwater in an otherwise dry and arid region. Oases (more than one oasis) are irrigated by natural springs or other underground water sources. They vary in size from a cluster of date palms around a well or a spring to a city and its irrigated cropland. Dates, cotton, olives, figs, citrus fruits, wheat and corn (maize) are common oasis crops. Underground water sources called aquifers supply most oases. In some cases, a natural spring brings the underground water to the surface. At other oases, manmade wells tap the aquifer. In some oasis settlements, these wells might be centuries old and might have been diligently maintained for generations to preserve access to their life-giving water. Sands blown by desert winds threaten wells as well as agricultural areas in oases. Sand can destroy crops and pollute water. Communities have traditionally planted strong trees, such as palms, around the perimeter of oases to keep the desert sands from their delicate crops and water. Some of the world's largest supplies of underground water exist beneath the Sahara Desert, supporting about 90 major oases there. The Sahara is the largest desert on Earth—about the size of the continental United States. Though there are many oases there, traveling between them can take days because the desert is so vast. For this reason, oases in the Sahara and throughout the world have become important stops along trade routes. Merchants and traders who travel along these routes must stop at oases to replenish food and water supplies. This means that whoever controls an oasis also controls the trade along the route—making oases desirable to political, economic, and military leaders. Al-Hasa, Saudi Arabia, has been an important farming area for the Arabian Peninsula for thousands of years. Today, it continues to be a leading agricultural region, producing dates, rice, corn, sheep, cattle, and eggs. The al-Hasa region also lies above one of the richest oil fields in the world, making the oasis an important center of international trade. Rivers that flow through some deserts provide permanent sources of water for large, elongated oases. The fertile Nile River valley and delta in Egypt, supplied with water from the Nile River, is an example of this type of large oasis. At 22,000 square kilometers, it might be the largest oasis in the world.
The Las Vegas Valley, in the U.S. state of Nevada, is a popular tourist destination known for gaming and entertainment. Before the arrival of casinos, however, Las Vegas was the site of a natural oasis in the Mojave Desert. Springs brought water from the regions aquifer to the surface, ultimately flowing into the Colorado River. Las Vegas means the meadows in Spanish, and was named when the oasis was discovered by Mexican merchants in The Las Vegas oasis has dried up. Development drained the springs. The areas empty aquifers are now used to store water from Lake Mead, an artificial lake created by the Hoover Dam on the Colorado River. Water is a major environmental and political issue in Las Vegas and throughout the U.S. Southwest.

6. South of the Sahara is the Sahel
Flat, semi-arid plain that serves as a transition zone on the continent of Africa
3,300 miles across