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sandstone

Imaggeo on Mondays: Natural Bridges Monument, Utah, USA

Imaggeo on Mondays: Natural Bridges Monument, Utah, USA

Slowly but surely, the force of water has carved out a beautiful landscape in the sandstones of the Colorado Plateau. Suspended over canyons, naturally formed bridges and arches are the starts of Utah’s first national monument. The geological and modern  history of the region is rich as Kimberly Galvez, a student of the University of Miami, describes below.

This image shows an overview of a portion of the Natural Bridges Monument in Utah, taken from the Colorado Plateau. In the lower center of the picture is the Sipapu Bridge, one of the 3 bridges within the national park.

The dominating sandstone comes from the Permian Cedar Mesa Formation that is part of the Colorado Plateau, a geologic province that extends through southern Utah and northern Arizona, northwest New Mexico, and western Colorado; with geologic units including the Lower Cutler Beds from the Pennsylvanian, Permian Organ Rock and Cedar Mesa Formation, Triassic Chinle and Moenkopi Formations, Jurassic Wingate Sandstone and the Quaternary alluvium.

Due to the regional uplift the Colorado Plateau experienced, meandering rivers progressively cut through the crossbedded sandstone – cross-bedding reflects the transport of sand by a flow of water over a river channel – of the Cedar Mesa Formation forming the bridges, leaving behind the exposed erosional surfaces carved out by the river.

Today, these bridges face many challenges: The region is still seismically active. Earthquake activity could lead to the collapse of (some of) the bridges and other small formations. Due to the low stability of the sandstone from the lack of anchoring from root structures, slope failures and slumps can be quite common and especially in the event of flash floods. Continuous wind patterns increase erosion and alter the exposed surfaces and the structure of the channel is constantly changing due to seasonal rainstorms.  Sediment transport and deposition, caused by streamflow, is a major factor in channel morphology and, therefore, the ecosystem of the Natural Bridges Monument.  The National Park Service constantly monitors the changes and issues that arise.

A final remark: Thanks to the entire group of the 2015 Annual AAPG Student Field Trip for making this photo possible. Members of the CSL – Center for Carbonate Research and the UM Student Chapter of AAPG for funds, and field trip leaders: Gregor Eberli and Donald McNeill.

By Kimberly C. Galvez, University of Miami – RSMAS

Imaggeo is the EGU’s online open access geosciences image repository. All geoscientists (and others) can submit their photographs and videos to this repository and, since it is open access, these images can be used for free by scientists for their presentations or publications, by educators and the general public, and some images can even be used freely for commercial purposes. Photographers also retain full rights of use, as Imaggeo images are licensed and distributed by the EGU under a Creative Commons licence. Submit your photos at http://imaggeo.egu.eu/upload/.

 

Imaggeo on Mondays: Through the hole

Imaggeo on Mondays: Through the hole

The Gunung Mulu National Park is an area so geologically remarkable and home to such incredibly diverse fauna and flora it has been declared a World Heritage Area.  Located on the island of Borneo, the park is famous for its over 100 different palm species and 3500 other plant types. Geologically speaking, a trip though the varied landscapes will be rewarded with views of deep gorges and hidden valleys, as well as towering limestone and sandstone pinnacles. The predominantly calcareous landscape means most make the journey to remote area to catch a glimpse of the world’s second largest cave chamber. With dimensions of 600 m by 415 m and 80 m high, Sarawak Chamber is a natural wonder worthy of making the journey to Borneo for!

“The picture was taken in February 2014 while I was on a two month trip to Indonesia and Malaysia after graduating from my Master studies. Eventually I found one of the most beautiful places on the island of Borneo: the Gunung Mulu National Park,” explains Juliane Krenz, a PhD candidate at the Department of Environmental Science of the University of Basel.

Aside from the staggering Sarawak Chamber, the national park is crisscrossed by at least 295 km of explored caves.  Made up of the Mulu Sandstone Formation, overlain by the Melinau Formation – which formed in coral rich lagoons some 20 million years ago – the caves are home to a host of species, from bats to swiftlets.

“After spending a few days exploring one of the largest cave systems in the world, I wanted to get deeper into the rainforest and climb Mount Api to see the so-called “pinnacles” – an incredible limestone karst formation everybody was talking about,” Juliane says.

The journey to reach the “pinnacles” involved an hour’s boat ride and three hours walk through the rainforest, eventually reaching a small base camp impressive for its setting: three houses next to a crystal clear stream surrounded by mountains covered in dense forest.

The hike to the sandstone spires began in earnest the next morning. To reach the impressive formations Juliane had to climb an endless number of natural steps made of slippery roots and stones of varying heights from a comfortable 20cm up to 1m, with a total elevation increase of 1200 m in little over 2km – turning the hike into an adventurous climbing trip.

“After 3 hours hiking mostly vertically we reached the top and looked down on an innumerable amount of silver-greyish rock pinnacles spiking out between the dense bright green forest, some of them being up to 40m tall. None of us would have guessed that there were so many,” describes Juliane.

Capturing the beauty of the setting was no easy task.

“I had seen many impressive photographs of the spikes but I was looking for the special focus. Eventually I chose the hole as a frame making the largest pinnacles look like they are part of a miniature world – like me wandering through the rain forest.”

By Laura Roberts Artal , EGU Communications Officer and Juliane Krenz, a PhD candidate at the Department of Environmental Science of the University of Basel.

For more information on the Gunung National Park:

In 1977-78 there was a large expedition (followed by many others known as the Mulu Cave project) founded by the Royal Geograpical Society to explore the dimensions of the cave system. The “pinnacles” at Mount Api are part of the limestone ridge between North Thailand and New Guinea.  The area is full of limestone spikes of various sizes (from few centimeters up to several meters) that are formed through weathering and dissolution over centuries. Nowadays, most research is focused on the ecology and biodiversity in the caves and the surrounding areas.

An earlier version of this post stated Sarawak Chamber was the largest cave chamber in the world. That accolade goes to Hang Sơn Đoòng in Vietnam. With thanks to @TerjeSolbakk for helping us improve this post. 

 

Imaggeo is the EGU’s online open access geosciences image repository. All geoscientists (and others) can submit their photographs and videos to this repository and, since it is open access, these images can be used for free by scientists for their presentations or publications, by educators and the general public, and some images can even be used freely for commercial purposes. Photographers also retain full rights of use, as Imaggeo images are licensed and distributed by the EGU under a Creative Commons licence. Submit your photos at http://imaggeo.egu.eu/upload/.

Imaggeo on Mondays: The organisation of a river system

Imaggeo on Mondays: The organisation of a river system

The picture shows the Elbe Rivervalley, one of the major rivers of Central Europe. It was taken from the Bastei Bridge close to Rathen, which towers 194 meters above the Elbe River in the state of Saxony in the south-eastern Germany. This region belongs to the national park known as Saxon Switzerland. Together with the Bohemian Switzerland in the Czech Republic, the Saxon Switzerland National Park forms the Elbe Sandstone Mountains, which represents the greatest cretaceous sandstone erosion complex in Europe and is popular with tourists and climbers.

The Elbe basin covers the largest area in Germany (65.5 %) and the Czech Republic (33.7 %). The smaller parts of the basin lie in the Austria (0.6 %) and Poland (0.2 %). It starts in the northern Czech Republic at an elevation of about about 1400 meters above sea level and flows via Bohemian, Germany, and into the North Sea at Cuxhaven. Therefore, the Elbe river system connects four countries as well as large German cities such as Dresden, Wittenberg, Magdeburg and Hamburg.

The sandstone of the Elbe Mountains was formed by accumulation of sands during a marine regression – a process where previously submerged seafloor becomes exposed due to receding ocean waters – (Cretaceous sea) millions of years ago. The varying sandstone formations that make up the mountains represent variations in pressure regime, horizontal structure and fossil content. After the marine regression, the developed sandstone formations were uplifted. The uplifted sandstone formations have been shaped by subsequent chemical and physical erosion and biological processes acting on the rocks. Moreover, the water masses of the Elbe River formed the valleys and streambeds. Therefore, the current state of the landscape of the Elbe Sandstone Mountains is characterised by the changes between plains, ravines, table mountains and rocky regions with undeveloped areas of forest. Human activity also plays an important role in the shaping of the highland region’s landscape as it is affected by settlements, tourisms and climbers.

The image illustrates how the interplay between long-term processes, such as geology, tectonic history, geomorphology, climate, biology and human influence shape landscapes.

By Tatiana Feskova, researcher at the Helmholtz Centre for Environmental Research.

Imaggeo is the EGU’s online open access geosciences image repository. All geoscientists (and others) can submit their photographs and videos to this repository and, since it is open access, these images can be used for free by scientists for their presentations or publications, by educators and the general public, and some images can even be used freely for commercial purposes. Photographers also retain full rights of use, as Imaggeo images are licensed and distributed by the EGU under a Creative Commons licence. Submit your photos at http://imaggeo.egu.eu/upload/.

Imaggeo on Mondays: The place where water runs through rocks

Imaggeo on Mondays: The place where water runs through rocks

Antelope Canyon, located in Arizona, USA, was formed by erosion of the Navajo Sandstone, primarily due to flash flooding and secondarily due to other sub-aerial processes (think of physical weathering processes such as freeze-thaw weathering exfoliation and salt crystallisation). Rainwater runs into the extensive basin above the slot canyon sections, picking up speed and sand as it rushes into the narrow passageways. Over time the passageways are eroded away, making the corridors deeper and smoothing hard edges in such a way as to form characteristic ‘flowing’ shapes in the rock.

The Navajo Sandstone was deposited in an aeolian (wind-blown) environment composed of large sand dunes: imagine a sea of sand, or an erg, as it is known scientifically, not dissimilar to the present Sarah desert landscape. The exact age of the Navajo Sandstone is controversial, with dated ages ranging from Triassic to early Jurassic, spanning a time period between 250 million years ago to approximately 175 million years ago. The difficulty in determining the exact age of the unit lies in its lack of age diagnostic fossils. The Navajo Sandstone is not alone in this quandary, dating is a common problem in aeolian sediments.

“The picture was taken during a three week Southwest USA road trip in summer 2012. One of the highlights was the visit to Antelope slot canyon, which is located on Navajo land east of Page, Arizona. The Navajo name for Upper Antelope Canyon is Tsé bighánílíní, which means the place where water runs through rocks,” explains Frederik Tack, an atmospheric scientist from the Belgian Institute for Space Aeronomy and author of today’s Imaggeo on Monday’s photograph.

The erosive processes which form the canyon are still ongoing. There is an elevated risk of flash floods, meaning the canyon can only be visited as part of guide tours.

“The canyon was actually quite crowded which made taking this picture challenging, especially as I wanted to capture the peace and solitude of the landscape,” describes Tack.

The effort was worth it: Waved rocks of Antelope slot canyon was one of the EGU’s 2015 Photo Contest finalists!

Imaggeo is the EGU’s online open access geosciences image repository. All geoscientists (and others) can submit their photographs and videos to this repository and, since it is open access, these images can be used for free by scientists for their presentations or publications, by educators and the general public, and some images can even be used freely for commercial purposes. Photographers also retain full rights of use, as Imaggeo images are licensed and distributed by the EGU under a Creative Commons licence. Submit your photos at http://imaggeo.egu.eu/upload/.