The Eye Of The Sahara: Richat Structure

The Eye of the Sahara, also known as the Richat Structure, is a prominent geological wonder in the Adrar Plateau of the Sahara Desert, Mauritania. It's not an impact crater, as once believed, but rather an eroded dome with concentric rings. It is about 40 kilometers (25 miles) in diameter and is visible from space.

The Richat Structure is a deeply eroded dome that exposes layers of sedimentary rocks that are up to 600 million years old. The concentric rings of the Richat Structure are formed by different layers of rock that have been eroded at different rates.

The Richat Structure of Mauritania has captured the attention of astronauts for about as long as NASA has sent humans into orbit around Earth. This circular geologic feature is thought to be caused by an uplifted dome—geologists would classify it as a domed anticline—that has been eroded to expose the originally flat rock layers.

Eye Of The Sahara
Richat Structure: Geological Wonder in the Sahara Desert, Mauritania.
Photo: European Space Agency

The Richat structure has been a case of scientific debate about the origin of ring structures in the world. There have been several studies to define whether it was an impact structure or intrusive feature.

The 40 km-diameter circular Richat structure is one of the geological features that is easier to observe from space than from down on the ground, and has been a familiar landmark to astronauts since the earliest missions.

How was the Richat Structure formed?

The exact origin of the Richat Structure is still debated, but it is believed to have formed around 100 million years ago. One theory is that it was formed by the impact of a large meteorite or comet. Another theory is that it was formed by volcanic activity.

However, the most widely accepted theory is that the Richat Structure was formed by a combination of uplift and erosion. Over time, the hot magma beneath the Earth's surface pushed up the crust, forming a dome. The dome was then eroded by wind and water, exposing the different layers of rock.

Richat Structure - Eye Of The Sahara
Richat Structure - Eye Of The Sahara
Landsat image of Eye of Sahara

Types of rocks in the Richat Structure

The Richat Structure is composed of a variety of different types of rocks, including:

Quartzite: Quartzite  is a hard, metamorphic rock that is made up of quartz grains. Quartzite  is the most resistant rock type in the Richat Structure and is  responsible for the concentric rings that are seen today.

Shale: Shale is a  sedimentary rock that is made up of clay and silt particles. Shale is a  softer rock type than quartzite and is more easily eroded.

Sandstone: Sandstone  is a sedimentary rock that is made up of sand grains. Sandstone is also a  softer rock type than quartzite and is more easily eroded.

Basalt: Basalt is an  igneous rock that is formed from the cooling of lava. Basalt is the  least common rock type in the Richat Structure and is found primarily in  the center of the structure.

Satellite image of the Richat Structure, also known as the Eye of the Sahara, a geological formation in the Sahara Desert.
Richat Structure.
Photo: NASA Earth Observatory


Geological Record: The exposed sedimentary layers serve as a natural record of Earth's geological history in that region, spanning hundreds of millions of years.

Visual Spectacle: The Richat Structure's large size and distinctive circular pattern make it a visually striking feature, particularly when viewed from above.

Scientific Inquiry: The Richat Structure has been a subject of scientific debate and research, contributing to our understanding of dome formation, erosion processes, and the geological history of the Sahara.

Close-up of the Richat Structure, a geological formation in the Sahara Desert, showing its concentric rings.
Richat Structure
Photo: NASA Earth Observatory

Comparison to Impact Craters

While initially thought to be an impact crater, the Richat Structure lacks several key features characteristic of meteorite impacts:

Central Peak: Impact craters often have a central peak formed by the forceful rebound of rock after the impact. The Richat Structure lacks such a peak.

Shattered Rock: Impacts typically generate extensive zones of shattered and brecciated rock, which is not as prominent in the Richat Structure.

Impact Melt: Impact craters often show evidence of molten rock formed by the intense heat of the impact. No conclusive signs of widespread impact melt have been documented in the Richat Structure.

In conclusion, the Eye of the Sahara stands as a fascinating geological feature, showcasing the interplay of uplift, erosion, and the vast timescales at play in shaping our planet's landscapes.

Eye Of The Sahara Photos

A photo of the Richat Structure at sunset, showing its vibrant colors.
Richat Structure - Eye Of The Sahara

View of the Richat Structure, a geological formation in the Sahara Desert, from the ground.

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