Currently, the total area of deserts around the world has reached 30 million square kilometers, accounting for 20% of the total land area. The Sahara Desert is the largest desert in the world, spanning northern Africa, with a length of 5,600 kilometers from east to west and a width of approximately 1,600 kilometers from north to south, covering an area of over 9 million square kilometers, which is about one-third of the total area of Africa.
The natural environment in the Sahara is extremely harsh – dry, with little rainfall and very unfavorable for survival, earning it the title of “the second largest desert in the world,” second only to Antarctica. Even today, if ordinary people cross the Sahara Desert without thorough preparation, they will undoubtedly face a near-death experience.
During the Ice Age, the Sahara was much wetter than it is today. Many species of animals and plants thrived here. However, today, except for the Nile Valley, where various vegetables can be cultivated, and a few other areas like the northern highlands near the Mediterranean that can grow olive trees, most of this region is not arable.
When a vast area of land remains in a state of extreme aridity for a long time, lacking vegetation and water, deserts, rocky deserts, gravel deserts (like the Gobi), and other types of deserts will form over time. The sand in the desert is created by the process of land desertification and rock weathering. This means that, regardless of how large a desert is, the thickness of the sand layer has its limits.
The thickness of the desert sand is related to the time of formation, topography, direction, and local wind speed. Deserts in different locations have varying sand layer thicknesses, and even within the same desert, the thickness of sand layers at different points can differ. Typically, the edges of the desert are where the sand is thinnest. According to statistics, the average thickness of deserts worldwide is about 3.5 meters.
The Sahara Desert covers most of North Africa, extending into 12 countries: Algeria, Chad, Egypt, Libya, Mali, Morocco, Eritrea, Sudan, Tunisia, Western Sahara, and Niger. Since 1962, the Sahara has expanded by nearly 650,000 square kilometers.
So, how thick is the sand in the Sahara Desert? What lies beneath the sand?
To determine how thick the desert sand is and what is beneath it, some might think we could explore this by drilling and digging deep into the desert, but there is a much more efficient, advanced, and accurate method available.
Electromagnetic waves can penetrate geological layers, and any material has different characteristics that reflect or radiate these waves. This means we can use electromagnetic waves to detect the bottom of the desert.
In reality, the depth of the desert also depends on various factors such as the time of formation, topography, direction, and wind force. In areas with many sand dunes, the depth of the sand also changes according to the movement of the sand.
This technology is known as remote sensing technology, which has been around since the 1960s. Initially, satellite and aircraft systems were used to transmit electromagnetic waves of specific frequencies to the desert, and then the spectral characteristics of the reflected electromagnetic waves were analyzed to identify geological features. After researching and processing the collected data, we can obtain information such as the thickness of the sand layer in the desert. This technology has wide applications, including exploring mineral resources underground, measuring ice thickness, and mapping seabed topography…
From the collected data, scientists have found that the average depth of the Sahara Desert is about 150 meters, equivalent to the height of a 50-story building (assuming each floor is 3 meters high).
<pAccording to remote sensing data, the thinnest layer of sand in the Sahara Desert is about 3.6 meters, while the thickest reaches up to 320 meters.
In reality, not all of the Sahara Desert is covered in sand; the sand-covered surface primarily lies in the Central and Northern areas, while the surface of most other regions consists of exposed rocks and gravel…
Besides the existence of oil in the Sahara Desert, there are still many remnants of ancient lakes and rivers beneath the desert sands. Geologists estimate that one of these enormous lakes, at its peak, covered an area of 108,000 square kilometers and was 247 meters deep.
These findings imply that for a long time, the Sahara was not a desert but a lush green paradise filled with vegetation and water, nourishing many species of animals and plants.
As for why this area transformed into a desert, scientists believe it is related to tectonic plate movements. Between 7 and 11 million years ago, the shrinking of the Tethys Sea (the ancient Mediterranean Sea) led to a significant weakening of the North African summer monsoon, gradually turning the ancient Sahara into a desert.
In reality, whether it is a desert, ocean, or other topographical features, if you remove water, sediments, etc., and dig deep into the Earth, you will eventually encounter hard rock. If we could excavate all the sand in the Sahara Desert, what would be revealed would also be hard rock.
The Earth is a rocky planet. Excluding the atmosphere and hydrosphere, the Earth can be divided into three layers: the crust, the mantle, and the core from the outside in. The upper part of the atmosphere of the mantle and the entire crust belong to the lithosphere. The entire lithosphere is about 60 to 120 kilometers thick, and the continental crust is thicker than the oceanic crust, but this thickness is still less than 2% of the Earth’s radius.
