Fish River Canyon

The Fish River Canyon, located in Namibia, is the largest canyon in Africa and the second largest in the world. It is one of Namibia’s most visited tourist attractions.

Encompassing a total area of 5900 square kilometres, the canyon is made up of a massive gorge which approximately 180 km long, 27 km wide and over 500 meters deep in some places. While it’s considered to be small when compared to the Grand Canyon in the US, it is still a sight to behold.

The forces of water, wind, ice, and gravity have contributed to the 650 million year formation of this masterpiece. The Fish River Canyon is made up of a wider upper canyon and a narrow lower canyon. The lower canyon was formed after erosion had finally worn through the hard *gneiss bedrocks.

650 Million Years ago, a north-south *graben was formed by plate movement. The ancient Fish River flowed along this graben and eventually eroded the sedimentary rocks along the graben edges away, leaving a flat plain which is now the upper canyon. Glaciation during the Karoo Ice Age (360 – 260 million years ago), caused the canyon to further deepen.

When Africa and South America separated as Pangaea broke up, Africa’s elevation rose considerably, increase in the gradient of the Fish River. This steeper gradient and faster water flow increased the power of the water and allowed it to begin eroding the lower canyon into hard, metamorphic gneiss* bedrock that had previously resisted erosion, cutting the inner canyon seen today.

Different colours of rock strata can be seen along the length of the canyon.

The river is generally dry but floods in the region’s rainy season which is usually between January and April.

The area is known to be a semi-desert with temperatures rising up 50 degrees Celsius during the day and dropping to just over 30 degrees Celsius at night. The average annual rainfall is 100mm. In the winter months, temperatures can be expected to drop below 0 at night, yet it can reach well above 30 degrees Celsius during by midday. Despite this temperature fluctuation, there are over 50 species of bird life spread throughout the canyon. In the lower regions, antelope and baboons can be seen. Sightings of leopards and mountain zebra have also been reported.

*gneiss – high grade metamorphic rock

*graben - is a depressed block of land bordered by parallel faults

-Renesh T

Image source http://bit.ly/1G9Um5H

References/Further reading http://bit.ly/1FYofAu

http://bit.ly/1D3sVmC

http://bit.ly/1G8LrOW

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Iceland’s Massive Dinosaur Rock

Located in North Iceland, in the Gulf of Húnaflói, stands a massive rock that looks like a grazing dinosaur called Hvítserkur. The spectacular structure is a natural formation on the landscape that adds an intriguing, mystical touch to the surrounding environment. In fact, legend has it that the colossal boulder was once a giant troll seeking to attack a neighboring abbey, but was petrified into a slab of stone when caught in the rising sun.

Whether one believes in folklore or not, it adds to the story of Hvítserkur, which used to be a volcano. The structure is the remains of a 15-meter-high volcano that has almost completely eroded away. Photographers both in and out of Iceland seek to capture shots of the beautiful, monumental rock.

(via My Modern Met)

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Six Beautifully Formed Natural Bridges

A natural bridge, also called a natural arch, is formed by erosion that occurs in massive, horizontally bedded sandstone or limestone. Some bridges, such as the Natural Bridge near Lexington, Virginia (picture 2) are formed by the collapse of a cavern’s roof that may leave remnant portions as bridges. Others may be produced by entrenched rivers eroding through meander necks to form cutoffs. Still others are produced by exfoliation and may be enlarged by wind erosion. Superb examples can be found at Rainbow Bridge National Monument (picture 3) and the Natural Bridges National Monument (picture 6), both in Utah.

sources 1, 2, 3, 4, 5, 6, 7

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Wind, ice and sand

Wandering along the beaches of an icy Lake Michigan, the photographer spotted these foot high baby yardangs (aka hoodoos) on the normally sandy beach. Dozens of these towers were rising up over what had been a flat expanse of sand, and the life cycle of this phenomenon reveals in a few days or weeks erosional processes that take many millennia or more in rocks.

The beach was frozen in the winter cold, solidifying. The ice (which is also a mineral) cemented the grains into a temporary, temperature mediated sandstone, in much the same way as calcite or silica from the waters that percolate the depths of the Earth do to sediments during their transformation into rock (a complex set of processes known as diagenesis). The howling winter winds then eroded the beach in the same way that they would a sandstone, but much faster than usual since ice is a lot softer than the usual mineral cements found in sedimentary rocks.

A couple of days later (these were taken on Valentine’s day), he returned to check on them, but a rise in temperature had dissolved them all, melting their icy cement.

Keep reading

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Seven Sisters Cliffs - East Sussex, England

The undulating cliffs known as the Seven Sisters rival even the White Cliffs of Dover for ivory clarity but the constant crashing of the ocean waves at their base is causing them to fall piece-by-piece back into the ocean.

Startlingly picturesque, the cliffs are known as the “Seven Sisters” due to the seven distinct hilltops that comprise the silhouette of the cliffs. The bright white color of the stone is thanks to the abundance of chalk that makes up most of the cliff face. The features were created in prehistoric times when the land was submerged and seawater pushed the softer chalk to the surface and as the waters lowered, exposed the cliffs. Now as the sea pounds the base of the cliffs each day, erosion is slowly taking the chalk back as large chunks of the cliffs wall back into the water. 

Luckily for the Seven Sisters Cliffs, it this very process of erosion that has allowed them to retain their white pallor since similar cliff faces around the world have received increased protection which halts the erosion, they have begun to accumulate vegetation that is slowly mottling their color. This has led to the Seven Sisters being used in a number of films such as Robin Hood: Prince of Thieves and Atonement.  

Visit the white cliffs of Seven Sisters on Atlas Obscura…

From Earth Science Picture Of The Day; May 21, 2014:

Spheroidal Weathering in Salt River Canyon, Arizona
Photographer: Stan Celestian; Summary Authors: Stan Celestian; Jackie Phillips

The diabase rocks in the Salt River Canyon of Arizona received their rounded shape through a chemical weathering process known as spheroidal weathering. The process begins as cracks in the rock guide the carbonic acid contained in percolating groundwater around corners and edges, slowly dissolving them away. The corners and edges of the original rock fragments become more rounded and spherical resulting in a rock that looks very much like it was shaped through stream transport. Over time the rock may become exposed at the surface through other various forms of erosion. Photo taken on April 20, 2014.

Durdle Door, Dorset, England.

“They persuaded me to keep on, and at last stranded me on the pebbles, exactly opposite the magnificent arch of Durdle-rock Door. Here I stood and contemplated with astonishment and pleasure this stupendous piece of Nature’s work” John O'Keefe, 1792.“

Located on the World famous Jurassic heritage coast, Durdle Door is a stunning, naturally formed limestone arch. The arch is on privately owned land, located near Lulworth, but it is open to the public, The name "durdle” comes from the old English “Thirl” which means bore or drill.

The geology making up the arch is composed of almost vertical bands of narrow limestone rock, which runs parallel to the chalk of the coast line. The arch formed as a result of the softer rock behind the limestone being eroded away (through joints in the limestone itself), and eventually the sea managed to punch through the limestone, leaving the archway. Eventually the arch will collapse, leaving sea stacks behind similar to those that can be seen all along the South West Coast.

The Bull, a rock sticking out from the sea, close to Durdle Door is a continuation of the rock strata found in the arch.

-LL

Links;
http://www.worldheritagecoast.net/place.aspx?place=25
http://www.southampton.ac.uk/~imw/durdle.htm

Image; Saffron Blaze