Columnar basalt is definitely beautiful and interesting rock formation but it is nothing new to a seasoned geologist. Columnar sandstone, however, is probably different story. I had never heard anything about such rocks when I accidentally just stumbled upon one.
There is a large “crater” named Makhtesh Ramon in the Negev Desert in Occupied Palestine . It is described as the largest makhtesh in the world. That really sounds impressive until you learn that these landforms actually occur nowhere else than in the Negev desert.
So it is simply largest in the Negev but it is impressive anyway. What is makhtesh? It is neither a meteorite crater nor is it a volcanic caldera although it is frequently described as a crater. It is an erosional landform of a structural dome which has softer rocks (sandstone) below and harder (limestone) on top of it. Intermittent rivers called wadis erode the softer rocks faster and create sharp escarpments like crater walls. Makhtesh Ramon has pretty impressive measures. It is 40 km long, 2-10 km wide and 500 meters deep.
The Ramon Crater is 40 kilometers long, but just a few kilometers wide. The craters were formed when the Arava rift valley was formed, and the rivers changed course, carving out the inside of the crater. The walls of the crater keep their vertical angle, while the bottom deepens, exposing ancient rock stata. The bottom of the crater is 500 meters deep, and the rocks at the bottom are 200 million years old!
Makhtesh Ramon no doubt is worth a visit in its own right but I was most impressed by what I saw in the middle of the makhtesh. There was a hill made of sandstone. But what kind of sandstone! It was like a huge pile of columnar logs. No wonder that this hill is named Ha-Minsara (The Carpentry Shop).
I don’t know exactly how it was formed but I believe the mechanism had to be very similar to the formation of a columnar basalt. Something had to provide lots of heat. There are volcanic rocks nearby in the crater, so it probably was magma. What else could it be? After this baking episode the sandstone slowly cooled and cracks formed when the cooling rock mass contracted. I’d be glad to hear if anyone has a better explanation.
Here are some pictures of Makhtesh Ramon and Ha-Minsara in the middle of it.
Source / Photos / http://www.sandatlas.org/
There is a large “crater” named Makhtesh Ramon in the Negev Desert in Occupied Palestine . It is described as the largest makhtesh in the world. That really sounds impressive until you learn that these landforms actually occur nowhere else than in the Negev desert.
So it is simply largest in the Negev but it is impressive anyway. What is makhtesh? It is neither a meteorite crater nor is it a volcanic caldera although it is frequently described as a crater. It is an erosional landform of a structural dome which has softer rocks (sandstone) below and harder (limestone) on top of it. Intermittent rivers called wadis erode the softer rocks faster and create sharp escarpments like crater walls. Makhtesh Ramon has pretty impressive measures. It is 40 km long, 2-10 km wide and 500 meters deep.
The Ramon Crater is 40 kilometers long, but just a few kilometers wide. The craters were formed when the Arava rift valley was formed, and the rivers changed course, carving out the inside of the crater. The walls of the crater keep their vertical angle, while the bottom deepens, exposing ancient rock stata. The bottom of the crater is 500 meters deep, and the rocks at the bottom are 200 million years old!
Makhtesh Ramon no doubt is worth a visit in its own right but I was most impressed by what I saw in the middle of the makhtesh. There was a hill made of sandstone. But what kind of sandstone! It was like a huge pile of columnar logs. No wonder that this hill is named Ha-Minsara (The Carpentry Shop).
I don’t know exactly how it was formed but I believe the mechanism had to be very similar to the formation of a columnar basalt. Something had to provide lots of heat. There are volcanic rocks nearby in the crater, so it probably was magma. What else could it be? After this baking episode the sandstone slowly cooled and cracks formed when the cooling rock mass contracted. I’d be glad to hear if anyone has a better explanation.
Here are some pictures of Makhtesh Ramon and Ha-Minsara in the middle of it.
Source / Photos / http://www.sandatlas.org/
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