The Kingdom of Sedimentary Rock

In May of 2014, an article I wrote about the Colorado Plateau appeared in the Society for Scientific Photography’s members’ magazine, which is published twice a year. The article contrasts the rather vertical and violent history of the Japanese Archipelago with the more horizontal and comparatively sedate history of the Colorado Plateau. The archipelago has a history of volcanoes that grew and collapsed and grew again, and mountain ranges that were uplifted through tectonic activity, and then cut by rivers. On the other hand, the Colorado Plateau has experienced mostly the deposition of sediments over nearly 2 billion years, with seas, river deltas, flood plains, and vast dune fields taking turns in providing different sedimentary deposits.

The article was conceived upon my return from Las Vegas in 2010 when I read through the books I had purchased about Zion and Bryce Canyons. During my brief stay, I had managed a few short trips to these places as well as Red Rock Canyon and Valley of Fire State Parks in Nevada. Pondering the very different geomorphology of Japan and the Colorado Plateau, I thought of how impossible it would be for such landscapes to have formed and developed in a tectonically active ocean archipelago. This I wanted to share with a Japanese audience.

The article was initially submitted to Nippon Kamera along with medium and large format film photographs. Six of the photos were published, but the article had to be trimmed down considerably. Still eager to share my whole story, I submitted it to the association of which I am a member. In the past, the magazine ran an article I wrote about alpine glaciers. So I was very pleased to see my latest work published as well.

Many thanks to Naoko Watanabe for checking over my Japanese and making it comprehensible and grammatically correct.

The Moler Load

The moler formation in Limfjorden in northern Denmark is a clay formation rich in diatoms that formed during the Eocene period. It is exposed along cliffs, particularly on the island of Mors, and in quarries on Mors. Volcanoes that were once located near the Faroe Islands erupted volcanic ash that fell into the sea, creating a suffocating layer that blocked out oxygen and buried the marine animals at the sea bottom. Fish, crabs, and many other smaller creatures can be found fossilized in the clay layers. Concretions known as cementsten (cement stone) can be spotted cropping out of cliffs such as at Hanklit. These concretions contain high concentrations of calcium and may have insect fossils. Many of the softer layers of clay in the moler are heavily bioturbated, disturbed by living organisms prior to the consolidation of the layers. Unfortunately, the burrowing creatures did not leave their fossils behind.

Most seabeds become uplifted due to the raising of the land by tectonic action. The molar formation, with its layers of clay and volcanic ash, can clearly be seen as intensely folded layers forming anticlines and synclines. Some of the most dramatic folds can be seen at the Skarrehage quarry. These folded sedimentary layers were not crumpled by tectonic activity but rather by the force of several glacial advances. Each glacial period saw ice sheets moving south from Norway and Sweden and as they ploughed south, they pushed and folded the soft seabed like a carpet.

The clay layers are quarried for their use as cat litter or making lightweight bricks; however, the quarry workers are on the lookout for rare fossils which are delivered to the museum across the road from the Skarrehage quarry. Fossil hunting is encouraged in Denmark and finds of minor consequence can be taken home. Unusual or rare finds should be turned in to the museum which offers some remuneration for the find. Both the Skarrehage and the Ejerslev quarries permit fossil hunters on weekends or in areas where the machines are not working.

For more information read the detailed and excellent article below:

ESNews

This site has photos and a map.

Fossil Location

And the Strahlen Foundation site has some good photos too.

Strahlen Foundation

The Goodness of the Badlands

In several arid and semi-arid places in the world one can encounter the bizarre-looking landscapes of clay and other sediments known as badlands. From French les mauvaises terres and closely resembling the Spanish word for a related but different landscape malpais, badlands are characterized by landscapes that look as though a clay bed sheet has been draped over many small hills and knolls, which sometimes rise into sharp knife-edged ridges and fins. There are usually rocks and boulders of sedimentary rock scattered about and sometimes these rocks end up as cap rocks on clay towers known as hoodoos. Badlands lack or have a very shallow regolith, which means there is little soil for vegetation to take root. The landscape is easily eroded by water and wind, and only hardy scrub plants such as sage brush and prairie grasses exist to a relatively moderate degree of abundance. Some flowering plants can also find a place to sprout in the cracks of rocks.

In the Province of Alberta, Canada is one of the most significant badland locations in the world. Sediments were laid down during the Late Cretaceous – from 75 to 65 million years ago – when the area was in a transition zone that was at times a shallow inland sea, a swamp, a river delta, or a flood plain. Over this period, prehistoric life left its remains in the sediments and the area is now said to be one of the two richest dinosaur fossil beds in the world, the other one being in China. Alberta’s badlands are at their most impressive and fossil-rich in Dinosaur Provincial Park, not far from the city of Calgary; however the Royal Tyrell Museum is located along the Red Deer River Valley just north of Drumheller. Farther south near Rosedale are the famous hoodoos with their cap rocks.

One interesting ingredient in the badlands clay matrix is the inclusion of a glassy igneous material resulting from volcanic ash fallout from the Yellowstone volcanoes. This material forms a crystalline clay-like mineral called montmorillomite and is the key ingredient in bentonite clay – a soapy, highly plastic clay which swells in water. When dry, bentonite clay is very hard. I once found a pencil sticking out of some dry clay but in spite of tugging with all my might I could not remove it. When wet, bentonite clay swells and becomes horrendously gooey. Walking on the stuff after a rain, I felt myself gaining height as the clay stuck to my boots. It is also terribly slippery and no fun to slide and fall down in. Easy to wash out with some serious scrubbing effort when wet, the clay cements itself to any surface when dry. If it gets between the fibres of the fabric of your clothes, it’s a futile effort to scratch it off with a fingernail, and a chisel is almost required to remove dried bentonite clay from a pair of boots.

The badlands are an exotic landscape to explore and rich in photographic landscape art potential. Go for the bones, stay for the photography!

Read more about the Alberta badlands

Read more about bentonite clay.

Tip of the Inselberg

It appears as a striking anomaly in a landscape of low dunes and flat horizons. The dome of Uluru looks unreal as it seems to be sitting as though it had been dropped from somewhere else onto the vast and flat desert of Australia’s Red Centre. Uluru is, however, not alone. A fraternal twin lies some 40 kilometres away – Kata Tjuta – quite different in appearance but born of the same mother, the Peterman Ranges.

As the geologists' story goes, the Peterman Ranges were much higher 550 million years ago, and erosion of these grand mountains produced two great alluvial fans, one of them consisting largely of river-rounded stones and the other of mostly sand. Over the next 50 million years, these fans built up layer upon layer, becoming kilometres thick. Then the whole area became covered by a sea and new layers of sediments fell on top of the fans. The weight of the new seabed turned the fans into rock – conglomerate for the rocky fan and sandstone for the other. Then some 400 million years ago, the Australian continent underwent considerable tectonic movement. The sea drained away and the layers of sediments were folded and tilted. The sandstone fan was tilted so that one end bent up at nearly 90 degrees. From 300 million years ago and on, the covering of sand and soil has slowly been blown away, exposing the harder rock of the ancient alluvial fans to the air. But what you see “sitting” on the landscape is just the tip of the iceberg, so to speak, or more accurately, just the tip of the inselberg.

Inselbergs are, according to the Encyclopaedia Britannica, an “isolated hill that stands above well-developed plains and appears not unlike an island rising from the sea.” Indeed, the name comes from German for “island” and “mountain” and was coined by early German explorers of southern Africa who were impressed by such landforms they encountered there. Inselbergs are often granite and other rocks of igneous origin, or other rocks that are more resistant and whose base lies well below the surface. While the surrounding soils and sands are gradually removed by the powers of erosion, the harder rock remains, slowly “rising” above the plains. As in the case of Uluru and its sibling Kata Tjuta, most of the petrified sediments still lie below the ground, possibly extending for several kilometres. Only a small portion of the total mass is exposed, making both landforms the lithological equivalent to an iceberg.

Incidentally, the sediments are not red in their unexposed state but rather light grey as the main components are feldspar and quartz, a type of sedimentary rock known as arkose. The exposed rocks turn reddish as their iron components oxidize with the air. This brings to mind the scene in the movie “The Hitchhiker’s Guide to the Galaxy” when for but a couple of seconds we see workers busy painting the grey rocks of Uluru red in preparation for the completion of the new Earth. Someone’s shot at a gag was not so far off from reality.

Hotspots and Large-body Impacts

The Kilauea volcano on the Island of Hawaii is one of the most active volcanoes in the world and visitors come to see the orange rivers of glowing lava that flow usually very peacefully – though sometimes aggressively and destructively – from the craters and vents and pours in dramatic cascades into the spitting and steaming ocean. The Island of Hawaii also includes two much higher volcanic peaks, Mauna Kea and Mauna Loa, whose eruptive activity has continued until fairly recently.

All the Hawaiian Islands are products of volcanism and the reason for their continued activity is a phenomenon called a hotspot. Hotspots are thought to be plumes of rising heat through convection currents within the mantle. The earth has 40-50 identified major hotspots and many minor ones, too. Hotspots remain in a relatively fixed position and so as the plates drift over them their product volcanic edifices are moved away from the up-welling magma and the volcanoes become extinct while a new volcano is born over the hotspot. The Hawaiian Islands form a chain of volcanoes with the Island of Hawaii comprised of the most recently active volcanoes, Maui’s Haleakala having been active until the recent past, and all islands becoming older as one moves northwest. On the ocean floor, a chain of extinct volcanoes and former islands extends across the Pacific, makes a change of direction halfway to Asia and continues on to its subduction zone at the far western end of the Aleutian archipelago. Other famous hotspots include the Yellowstone Caldera and Mount Etna.

What exactly are hotspots and what causes them? Two theories are that they are either deep mantle plumes or shallow plumes. But a new hypothesis is being tested that would suggest the origin of at least some of earth’s hotspots is large-body impacts. According to the paper by Johnathan T. Hagstrum, most of the earth’s major hotspots have antipodal hotspots or large igneous provinces (LIPs) of roughly the same age. The paper examines evidence that could suggest that a bolide of greater than 20km diameter striking the earth in an ocean could penetrate into the mantle and disturb it enough to create long-term volcanic activity where eruptive magma would cover any evidence of the impact crater. Furthermore, such a large impact would create Rayleigh shock waves that would spread around the globe and converge at the antipode of the impact. This convergence of seismic energy could fracture the crust sufficiently so as to lead to eruptive activity. One significant point is that most hotspots have antipodal LIPs, which suggests that if a large-body impact created the hotspot then the seismic energy focused at the antipode possibly triggered the basalt floods that created the LIPs. Another point is that in the case of continental impacts, the tensile strength of the thicker continental crust acted as a shield that prevented the creation of an antipodal hotspot or basalt flood. Only very large continental impact sites have antipodal hotspots. The paper offers a lot to consider.

So how about our Hawaiian hotspot? Its antipode is Lake Victoria in Africa; however, the research paper says that some antipodal hotspots are just coincidental and in the Hawaii/Lake Victoria case this seems to be the situation.

For further reading:

Hotspots

Antipodal Pair Impact Hypothesis

A post of mine about meteor craters

The Perito Moreno Glacier

Listed as one of the Seven Wonders of South America, the Perito Moreno Glacier is indeed a sight and sound to behold. From the viewing deck built up on the slope the view of the glacier is phenomenal. Between the mountain peaks emerges a 30-kilometre-long river of ice that stands on average 60 metres above the waters of Lago Argentina and stretches roughly 5 kilometres from side to side with a total surface area of about 250 kilometres squared. The view is nothing less than mind-boggling and at the same time both awe-inspiring and almost forbidding. It looks as though some frozen hell has breached its restraining barriers and has come flooding into our world. This incredible view has the air charged with sound as tremendous cracks and gunshot booms emanate from the seemingly static towers of ice that are actually slowly advancing forward into the frigid lake waters and bending under their own weight. Large chunks of ice break free and plunge into the lake with a splash that sounds like a semi-trailer truck was dropped in, and if you can watch long enough you might even see a huge section collapse into the lake with a thunderous rumble and a splash that sends tsunami-like waves rolling across the water.

The Perito Moreno issues from the Southern Patagonian Icefield, the third largest freshwater reserve on the planet. It is one of only three Patagonia glaciers that is still growing. Though the articles say that scientists are still not certain why the glacier is growing while most others are retreating, I think it may be a combination of factors such as proximity to the regions of the icefield that receive the most precipitation, wind direction in relation to the surrounding mountains, and the presence of self-produced cloud cover. Icefields tend to make their own climate, cooling the air over them creating clouds when the air is moist and causing rain or snow to fall while neighbouring mountains and plains remain dry.

Aside from its impressive visual appearance, the Perito Moreno glacier is also famous for its spectacular ruptures. The glacier’s trajectory pushes it against the rocky headland where Lago Argentina branches into the main lake and an arm known as Brazo Rico, and once the ice has built up against the rocks, the melt waters in Brazo Rico cannot escape into the rest of the lake. The water level rises and it can reach up to 30 metres before the water forces a way through in with a crashing collapse of ice and an explosion of ice-chocked water. The pent up waters surge through the opening sending icebergs swirling and bobbing into the main body of the lake. This extraordinary event may occur as frequently as once a year to as infrequently as once every several years.

The Primrose Terrace and the Wai-O-Tapu Geothermal Area

There are many places in the world where near-surface geothermal activity causes silicates to bubble up with hot water and then to be precipitated as the hot water trickles away or evaporates. Where these siliceous precipitates are deposited, impressive structures of delicate miniature pools and terraces are formed. Perhaps the most famous is the Mammoth Hot Spring terrace of Yellowstone National Park. In the southern hemisphere, New Zealand’s North Island has some of the most impressive geothermal features, particularly around Rotorua and Wai-O-Tapu.

The Wai-O-Tapu area includes a variety of natural features such as hot spring pools, bubbling mud pots, collapsed craters, and a sinter terrace known as the Primrose Terrace. This is the largest known sinter terrace (1.5 ha) in the Southern Hemisphere, since the Pink and White Terraces were destroyed in 1886 by the eruption of Mount Tarawera. The siliceous sinter flows in hot water from the Champagne Pool, which gets its name from the carbonic gases that bubbling out of the 73-degree water. Microbiolites and microstromatolites play an important role in the silicate precipitation by providing templates for silica precipitation. Around the Champagne Pool, various elements provide the colours of the rich pallet, including colloidal sulphur and ferrous salts (green), antimony (orange), manganese oxide (purple), silica (white), sulphur (yellow), iron oxide (red), and sulphur and carbon (black).

The Wai-O-Tapu area is associated with volcanic activity dating back to 160,000 years ago. The Champagne Pool is much younger, only about 900 years old, and the Primrose Terrace is believed to have been forming only for the last 700 years.