Monday, July 24, 2017

Filming at a Sandstone Gem in Northern Arizona

This past weekend, I was asked to take part in a Japanese TV production at the Vermilion Cliffs, a remote location in far northern Arizona. I was asked to serve as geologic interpreter for the longest running Japanese TV Travel Documentary program, titled “Sekai Fushigi Hakken (Discover the Wonders of the World), which has been airing in Japan since 1986. This is my second Japanese television project I have worked since last November. I was to explain how this extraordinary landscape came to look the way it does.


Setting up the initial shots. We had to drive for 90 minutes on a very bad road just to attain the trailhead. Then it was a short walk into the rocks.

This was the host of the show who was in front of the camera explaining the geology.

The area boasts some of the strangest forms I have seen in sandstone outcrops and it is easy to see why they wished to film here.

There are lots of exposures of Navajo Sandstone in the Arizona and the American Southwest. But I think they were drawn to this particular area because of the fantastic shapes, which can be explained geologically.

To start with, the Navajo Sandstone was deposited during the Jurassic, about 190 million years ago. It's obvious textures show that this part of North America was a vast Shara-like desert in which huge dune fields abounded. These are essentially petrified dunes.

Close-up of the cross-bedded sandstone. Cross-bedding indicates the current direction - in this case air or wind. The direction that the cross-beds dip indicates the ancient wind direction. Here we can see that the wind was blowing from left to right. It is the leeward side of the dunes that are preserved. The US quarter for scale lies within a bed of sand that has variable grain sizes, while the thin wisps that stick out in relief are of one particular size. The interpretation is that variably-sized layers resulted from sand avalanches that slid down from the crest of the dune. In these avalanches, variably sized grains intermix. (See the picture immediately below). The thinner but single size layers are the result of gentle winds blowing across the dune face in between avalanches. The wind segregates the sand grains to a particular and specific size. As all of this texture sits buried, groundwater moves through the sand and leaves variable amounts of cement, ultimately causing this feature when the rock becomes uplifted, exposed and weathered. This was quite a bit of information to relate to a travel variety show but our host was most gracious and seemed to be impressed with the information (relayed through a translator).

The next two photos are from the Namib Desert in southern Africa. This one shows the extent of this great desert, which makes for a good modern analog of the Navajo erg (sand sea) that was present in the American Southwest during the Jurassic some 190 million years ago.

Here are examples of sand avalanches from the dune field in Namibia, with sand avalanches seen on the leeward side of a dune. Note the tongues of sand that have naturally cascaded downhill when the slope of the dune became too too steep.

And all of this is just the first part of there story! The previous could explain most Navajo Sandstone outcrops anywhere on the Colorado Plateau. Here in the Vermilion Cliffs however, a few beds of sandstone were involved in a prehistoric landslide that disrupted the layering before they became cemented. In the middle of this rock, you can see the reddish contorted beds riding up and over the in-place beds below and above. This is what gives this area its unique attraction.

Close-up view of the mobilized bed of sand (main part of the picture with brownish rock) with an intact and undisrupted cross-bedded sandstone riding on top of it (upper left). Note the clast of cross-bedded sandstone (lower right) that was broken off from its main counterpart and lodged as a separate clast within the disrupted beds.

Overturned sandstone involved in a Jurassic-age slump event. The slump could have been initiated by an earthquake or slippage along a wet horizon (or both).

Small-scale faults disrupt the cross-bedding. Features like this suggest that the sediment was somewhat consolidated and partially brittle. The extreme folding elsewhere indicates that it was not completely lithified.

A plant called rockmat (Petrophytum caespitosum) in the Rose family, grows where water seeps out of the rocks and adds a touch of green to an otherwise red landscape.

The mobilized bed appears as whitish sandstone on the very top of this outcrop with partially faulted and bent layers below.

Another great feature of the area is the polygon in the sandstone. Many of these are pentagons or hexagons and are reminiscent of the columnar jointing found in basalt rocks. These however are not cooling fractures but form from the expansion and contraction of the sandstone surface or shrinkage related to the inclusion of clay grains in the sandstone (the former cause is more likely in this case). Here we see polygons within polygons.

I often refer to these textures as "biscuit" rocks, since they appear like a pan of freshly cooked biscuits.
Don't forget the B roll!

The host walking on the biscuit rocks.

This was an enjoyable project to work on and I am thankful for TV-man Union in Japan for using my services. The feature will air in Japan on September 23 at 9 PM.

Saturday, June 24, 2017

Traveling to Iceland with Smithsonian Journeys

I've been in Iceland for the last week, lecturing on a Smithsonian Journeys natural history tour. This is the same itinerary I participated with in September of last year and many of the places visited are the same from that trip.

Hraunfoss (literally Lava Falls) near Reykhold. The dark line of rocks above the falls is a porous post-glacial lava flow that spread over and above an older, denser lava flow. Snow and rain water seep into a shallow water table and emerge at the contact of the two lava flows.

Near Arnarstapi on the Snæfellnes Peninsula. Note the color and texture difference within this single lava flow in the high cliff. The top (orange) part is called the colonnade and the gray lower part is called the entablature. The irregular joint pattern in the entablature is due to water seeping into the flow while it was cooling. The colonnade cooled in the absence of water. In the Grand Canyon and elsewhere, these textures may be reversed when river water flowed over the top of cooling lava flow.

This lava flow erupted in sea water during the last glaciation (more than 10,000 years) and the lower part of the flow became protected when it cooled and so the colonnade is located on the bottom.

Beautiful coastline on the Snæfellnes Peninsula.

The bay at Arnarstapi and a highly eroded lava flow.

Iceland flags over the North Atlantic Ocean.

At Lóndrangar along the southwest corner of the peninsula, one can view the inside throat (or core) of a volcano. The towers are the eroded remnants of the vent material, with the whitish cliffs to the right composed of tephra (ash) erupted from the vent.

We were very fortunate to travel the whole day on the peninsula with the geologist who made the geologic map of Iceland, Haukur Jóhannessen. Traveling with his map allowed me to know what rocks we were looking at during the entire trip.

Sitting in the North Atlantic, one is never far from bad weather in Iceland. But it does have a certain drama to it.

We visited the Volcano Museum in Stykkisshólmur and saw this engraving of the Snæfellnes volcano by Carl Emanuel Larsen, completed in 1845. Note the three-masted ship anchored in the bay to the right.

Near Stykkisshólmur, this rhyolite volcano exposed colorful rocks.

And then Haukur mentioned that this was the site of an ancient landslide, which I have outline here on the same photograph as above. For more pictures of the Snæfellsnes Peninsula, see my blog posting from September 25, 2016 here. Now we move on to the North Coast of Iceland.

Leaving the town of Akureryi headed to the North Coast.

In the little town of Husvik, a monument to the training of the Apollo astronauts in 1965 and 1967.

Atlantic Puffins (Fraturcula artica) nest on the hillside facing the north shore of Iceland near Tjörnes. People love puffins!

A view of the pseudo-craters at Lake Myvatn, where hot lava poured over marshy ground about 2,800 year ago, causing stream blasts that created these "rootless" cones. Features like this are often called maars in North America.

The geothermal area at Lake Myvatn. My-vatn means midge-water in the Icelandic language and we saw zillions of them. They do not bite but swarm around everywhere.

Dettifoss waterfall, considered Europe's largest.

At Dettifoss, the car park is about 1/2 kilometer away from the falls and one must walk across this channel of an outburst flood, which in Icelandic are called Jökulhlaups.

This outcrop is located to the west of the car park and is the highest deposit from the outburst flood.

I have outlined the extend of this channel (above) but the floods were much bigger than this. Three of them have been documented since the end of the last Ice Age coming to the north from the Vatnjökull glacier.

The geothermal area at Hvirir has lots of steam vents, boiling mud pots, and hissing springs.

Here, sulphur deposits ring the openings in a steam vent. I like the smell of the Earth's interior!

View to the south from near Lake Myvatn. The giant Skjaldbeiđur shield volcano looms on the horizon. For more pictures of the North Coast of Iceland, see my blog posting from September 27, 2016 here. We now move to the South Coast where I experienced my best weather ever for this part of Iceland.

The Gulf Stream rams against the south shore of Iceland making this the wettest side of the island. Consequently, there is much greenery here along with hundreds of waterfalls.

Skógarfoss on the South Coast.

The Alaska lupine was brought here in 1885 but was planted widely to control soil erosion beginning in 1960. It is now rampant across the landscape, outcompeting native species.

It is a beautiful plant however.

South Coast view across a lupine field.

Flowers on top of the basalt columns near Reynisfjara.

Sea stacks at Reynisfjara are the eroded remains of a volcanic vent.

Hyaloclastite rocks (lava quenched after erupting into water or ice) have tumbled down onto the black sand beach here.

Close-up of a hyaloclastite.

Top view of basalt columns at Reynisfjara.

Typical Icelandic scene on the South Coast.

The church at Vik, the southernmost town in Iceland.

Sejalandsfoss.

This waterfall can be accessed from behind and when doing this, a rainbow sometimes appears.

Mt. Hekla, Icelands most dangerous volcano. It last erupted in 2000 and poses a major threat due to its explosiveness.

On our last day we visited a geothermal plant where they had a great rock collection from the island.

A section of insulated pipe that brings hot water to Reykjavik.

It looks like a street map of Reykjavik but it is actually a map showing the hot water distribution system in a typical neighborhood.

The turbines are powered by steam.

Geothermal plants are very carbon-friendly and only generate about 15% of the CO2 that an equivalent carbon-fueled plant would make. However, Iceland is a very forward-looking country and this amount is deemed unacceptable. So the geothermal companies have developed a way to inject the CO2 back into the volcanic rocks, setting up a chemical reaction that deposits limestone on the basalt (the white on this basalt rock).

I highly recommend a visit to this fascinating country and will be leading another tour for Smithsonian Journeys July 5 to 15, 2018. Whomever you go with and whenever you go, take a geologist with you - there is so much to see and learn about.

Mike DeVault took this picture of me at the end of our trip while visiting Reynisfjara. Thanks Mike!