Using radar to measure the depth of the Sahara desert, scientists discovered a giant 'thing' below

The earth has a lot of continents covered with sand. In particular, the desert is a place where a lot of sand accumulates. There is so much sand in the desert that they are likened to "rivers" and even "oceans". Referring to the desert, we cannot help but mention the Sahara, the largest desert in the world.

What is used to measure the depth of the Sahara?

The Sahara Desert was formed about 2.5 million years ago. The Sahara Desert covers most of North Africa, stretching to 12 countries: Algeria, Chad, Egypt, Libya, Mali, Morocco, Eritrea, Sudan, Tunisa, Western Sahara, Niger. It is about 1,600 km wide from north to south and 5,600 km long from east to west, with a total area of ​​more than 9,000,000 km2, accounting for 32% of the total area of ​​Africa, the Sahara is indeed the largest desert. According to scientists, the Sahara desert is expanding more and more. Since 1962, the Sahara desert has expanded by nearly 650,000 square kilometers.

The Sahara Desert is one of the largest deserts in the world.

But that's the length and width, so how deep is the Sahara? If you dig up all the sand of the Sahara, what will be underneath?

In fact, for deserts with a relatively shallow depth, we can completely measure it by using a drill or digging directly with an excavator. But the Sahara desert has such a large scale, the above methods are completely unfeasible. The drill can be buried in the sand.

Scientists have shown another option is to use radar technology to measure the depth of the Sahara. Specifically, the radar depth sensor will emit electromagnetic waves transmitted to the sand surface. Then the wave will hit the sand surface to be measured and reflect back to the sensor. The sensor will process and calculate and give measurement results accurately and quickly.

In fact, the depth of the desert depends on other factors such as the time of formation, topography, direction and wind force. In areas with a lot of sand dunes, the depth of the sand also changes with the movement of the sand. Therefore, it can be said that the depth of the Sahara is not fixed. And using radar technology can easily measure the depth of different locations in the Sahara.

It is not possible to use an excavator to measure the depth of the Sahara.

From the collected data, the scientists found that the average depth of the Sahara desert is about 150 m, equivalent to the height of a 50-story building (calculated by the floor height is 3m) and the depth even up to 320 m. Perhaps this depth of the Sahara is the greatest and no desert on Earth can surpass it.

With such a vast and deep desert, the sand reserves are certainly astounding. So how do we determine what's underneath the Sahara?

What's Beneath the Sahara?

Many people wonder, why not transport all the sand in the desert to use for construction. Unfortunately, the sand of the desert is not the same as the sand used for construction. Desert sands are so fine and smooth that they don't have enough multidimensional chemical bonds. For small sand grains, it will be easier to mix, but the mortar will be slippery and less durable. Moreover, when the sand is dry, the load capacity is better, and when wet, the connection between them is easily broken, causing the sand layer to collapse.

The sand of the desert is too fine and smooth to be used in construction.

In addition, the alkali content in the desert sand is too large, it is easy to react chemically with other substances, affecting the quality of the work. Specifically, if the durability and safety of the building is not guaranteed, the consequences will also be very serious.

Moreover, it is very difficult to dig sand in a desert as large as the Sahara.

• Firstly, there is so much sand in the Sahara that it will take a long time to dig.
• Second, it is not easy to move all the sand in the Sahara Desert and it is also difficult to find a place to store it all. But suppose, if it were really possible to dig up all the sand in the Sahara, what would be underneath?

First, let's learn about the formation of the desert. Geologists have determined that the origin of sand in the desert has a long and complex history. They are formed from large rocks such as granite, gneiss and sandstone.

The unique feature of the desert is the difference in temperature of day and night. The sudden change in temperature caused the rock structures to be compressed by pressure causing them to crack. The climate in the desert is too arid, moreover, plants cannot grow here, so the rocks have no cover. The longer the time, the smaller they are crushed. Part of the finished products after being weathered will be dissolved. Minerals that are not affected by atmospheric agents such as quartz-silicon oxide and undissolved debris will be saved and transformed into desert sand.

At the bottom of the desert is a bed of bedrock that has not been weathered.

However, weathering takes place only on the surface of the desert. Below the ground, the weathering will become weaker and weaker. Therefore, when digging desert sand with increasing depth, scientists often encounter sand grains of increasing size. Sometimes they are no longer sand but lots of rocks and gravel. If we dig deep enough, we can dig up to unweathered rock and sometimes very valuable mineral deposits. These large, unweathered rocks are called "base rocks".

Digging to the location of this bedrock can be considered as digging to the bottom of the Sahara. However, this is only an answer to the material composition of the Sahara. In fact, the overall topography of the Sahara desert has many traces of rivers and lakes beneath the sand.

This ruin can be seen from satellite photos. NASA scientists once made a satellite map of the Sahara from images provided by the space shuttle Columbia's synthetic aperture radar. This synthetic aperture radar was placed on the space shuttle for the purpose of capturing images of the Sahara desert. This radar is an Earth observation system with certain surface penetration capabilities, which can record images of the Earth's surface from high altitudes. Through the satellite map provided by the Columbia ship, it can be seen that at the bottom of the Sahara desert appears the ruins of a huge ancient lake.

In fact, the overall topography of the Sahara desert has many traces of rivers and lakes beneath the sand.

According to calculations by scientists at NASA, the area of ​​this ancient lake is up to 108,000 square kilometers. It is about 247m deep. Even when narrowed, its area still reaches 48,000 square kilometers and is about 190 meters deep. In addition, this massive lake is just one of several ancient riverbeds and lakes that have been found by Columbia's composite aperture radar.

This study has also shown that the Sahara is not just a desert. Which 5,000 to 6,000 years ago, the Sahara was an area of ​​alternating deserts and oases. The Sahara Desert is a wet area with a lot of trees and animals. Archaeologists have found numerous dinosaur fossils and even human artifacts in the depths of the Sahara.

A team of American scientists from Stony Brook University has published research showing that the Sahara was once home to a lot of marine life. The team conducted the study based on records of British expedition teams in the early 1980s as well as fossils collected from the Sahara desert.

Not only rocks, scientists also found many different fossils in the heart of the Sahara desert.

According to paleontologist Maureen O'Leary, her team found fossils of catfish and sea snakes in the desert part of Mali's territory. She also added that 50-100 million years ago, northern Mali was mangroves and home to many species of mollusks. During the late Cretaceous and early Paleozoic, molluscs evolved into giant sea creatures, such as the 1.6 meter long catfish, the 12 meter long sea snake and the long bony pycnodont fish. 1.2m.

In 1902, archaeologists also found a 36-million-year-old fossil of a whale lying in the middle of the Sahara desert in the territory of Egypt. When searching for more fossils in this area, people continued to discover more whale bones in a depression that later became known as Wadi Al-Hitan, meaning Valley of the Whale. Scientists believe that the intense tectonic activities in the history of millions of years have caused the seabed to rise and turn this area into the continent it is today.

However, the "oasis period" then ended. Scientists think that the cause of this change is the precession motion of the Earth. Specifically, because the Earth has changed its tilt angle from 22.1 degrees to 24.5 degrees periodically.

Fossils of ancient animals were found under the sands of the Sahara.

Precession is the slow and gradual change of the Earth in the direction of the axis of rotation. This motion is due to the torque exerted by the Earth and Sun systems. This motion directly affects the tilt at which the sun's rays reach the Earth's surface. The tilt of the Earth's axis is 23.43 degrees.

From this, we can understand that the axis of rotation of the Earth is not always towards the same star (Pole) but rotates clockwise which causes the Earth to move similar to the motion of a star. turn. One complete rotation in the precession axis takes about 25,700 years.

The precession motion of the Earth will cause periodic changes in the amount of solar energy received by the Sahara and its surrounding areas. And the Sahara's summer monsoons frequently change from strong to weak and weak to strong. Thus, as the summer monsoon got stronger, the oases above the Sahara were turned into arid deserts.