Week 3 - Deserts: The Gobi Desert

Khongoryn Els sand dunes in the Gobi Desert. August 1, 2008.

Photo credit: Zoharby

The science behind desert formations has always piqued my interest, especially since so many vast deserts are formed in close proximity to densely vegetated tropical regions. After conducting some research on the matter, I discovered that the formation of deserts is due mainly to how air releases precipitation when it rises and cools. The defining characteristic of a desert is low precipitation, so it makes sense why this natural process would be the key contributor to a desert’s formation. But why then do many of Earth’s deserts surround the equator?

At the equator, the sun is positioned directly overhead, and therefore its solar rays shine straight down on the exposed areas. This direct sunlight causes intense heating, which – as a result – forces the affected air to rise rapidly. The air cools naturally as its elevation increases, and much of the air's stored moisture is released as a result. By the time the air shifts to another nearby location, it has lost a majority of its stored precipitation. This is why areas near the equator are typically starved of moisture. 

For this travel journal I chose to write about the Gobi Desert, a massive desert in Asia that spans over 500,000 square miles. Unlike most well-known deserts, the Gobi Desert does not consist primarily of sand. In fact, only about 5% of the desert’s surface area is occupied by sand dunes; the remaining 95% is covered in rocks and large dry grassland. One unique fact about the Gobi Desert is that – due to its close proximity to the Siberian Steppes – the desert is often covered in snow during winter months.

The formation of this desert is due mainly to a principle called the rain shadow effect, which is similar to the equator phenomenon described earlier. Rain shadow occurs as a result of air rushing over a nearby mountain range, and - in the case of the Gobi Desert - the range responsible is the Himalaya mountain range. As air climbs these mountains, the natural cooling effect associated with rising elevation forces the air to dump most of its stored moisture. The air is cool and dry when it descends back down the other side of the mountain range, which leads to the formation of a desert region.