Yoash Lookout

Some of the mountains you are seeing are of crust rock that was welded together some 900 to 700 million years ago and which is usually tens of kilometers below ground. Originally, this was volcanic rock and sediment called “igneous” or “magmatic rock” that changed into “metamorphic rock” because of immense heat and pressure. It is colored dark gray, greenish and black because of its content of iron-rich minerals and the alteration of its structure due metamorphosis.

 

Look carefully at this dark rock and you will see cutting through it narrow, straight bands that are even darker than the surrounding rock. They are called “dykes” and are due to injection of magma through fractures in the rock as a result of stretching of the crust. They are black, dark gray and dark green due to their rich iron and magnesium content.

 

How did this metamorphic rock reach the surface of these mountains rather than remaining deep below the ground? The reason is that it was once covered by sedentary rock, such as the limestone one sees in the Judean Mountains; but this eroded away, exposing the basement underneath. The limestone was formed when this area was covered by an ancient ocean.

However, this is not the end of the story. About 30 million years ago, the Arabian Plate began pulling away from Africa, as part of the Syrian-African Rift system. This resulted in blocks of crust being uplifted (“horsts”) and others dropping down (“grabens”). The most obvious example of this descent is the Arava, but this process also occurred beyond the Arava. Mount Yoash is an uplifted block, and this is what gives it a commanding view over Eilat and the Gulf of Aqaba.

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The sharp jagged skyline of the surrounding mountains is from the gradual fracturing away of this igneous rock due to flash floods which carved deep wadis (dry riverbeds), and also from extreme temperature changes that mechanically cracked the rock. The minimal vegetation also permitted continuation of this slow erosion process.

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Without the rift, these rocks would still be buried deep underground. If you look towards the mountains of Jordan that are beyond the Arava, the rocks are of the same age and landmass, and constitute part of a single geological unit.