Wednesday Rocks: #3

As this Wednesday Rocks being posted 40 minutes into Australia Day (Thursday 26th January) it's fitting that the subject is Australian.

Springbrook National Park, Queensland.

Natural Bridge

In November 2011 we took a drive south of Brisbane into the SE Queensland / NE New South Wales Hinterland (-28.202768,153.249664 - just enter the coordinates into the Google Maps search bar). Our exploring took us to Natural Bridge in the Springbrook National Park (I keep seeing Springbok but that's a result of my eight years living in South Africa). The rocks at Springbrook are part of a ~20Ma shield volcano which forms the Tweed Province, a series of basalt and rhyolite lava flows. Natural Bridge is an erosional feature formed behind a waterfall (Willmott, et al. 1981). 

A river runs through it, the top of the waterfall.

I assume that the formation is the result of a pothole or kettle forming behind the lip of the waterfall, as evident in the photo above. The rocks possibly faced a four-pronged attack from above, the pothole, below, the falling water eroding the rocks at base of the falls, water eroding joints and fractures in the rocks and then continued erosion by the waterfall. However, these processes are not something I've looked at in detail for a couple of years so feel free to drop suggestions in the comments box.

The cave at Natural Bridge is 46m long, 26m wide and 6m high (Webb, et al). It is famous for glow-worms and bats neither of which were in residence on our visit.

Willmott, W.F, Webb, J.A. and Wade, M. (Eds), 1981. Geological Sites in Southeast Queensland, Report 2. Geological Elements of the National Estate in Queensland, Geo. Soc. Aust. Inc. Queensland division, Brisbane, pp 119.

Tweed Valley
Happy Australia Day!! :)

Wednesday Rocks: #2


As I have mentioned before, New Zealand's North Island is rife with volcanic activity. I spent part of December and January on the North Island and part of that time was spent camping near Rotorua. Rotorua is part of the Taupo Volcanic Zone. Volcanism here is related to the subduction of the Pacific Plate beneath the Australian/Indian (depending on your source) plate. The volcanic zone has four recent andesite or dacite calderas which are, in order from west to east; Taupo, Maroa, Okataina and Rotorua. Maroa is the largest and Rotorua is the smallest (Cole, 1984). These calderas are situated in the Taupo-Rotorua depression and evidence suggests that the depression is the result of extension (Cole, 1984).

The photos below are from the Whakarewarewa Geothermal Village which is the happy marriage of New Zealand culture and geology. The village is home to the Tuhourangi/Ngati Wahiao people who use the geothermal springs for cooking, bathing and hot water. The village has been open to visitors since the beginning of the 19th Century and is definitely worth a visit. The people of the village are fantastic and the guides very knowledgeable. While we were at Whakarewarewa we had a hangi, a traditional Moari meal cooked using hot stones. At Whakarewarewa the hangi is unique as it is cooked using the heat from the geothermal system. One of the geothermal pools is also used for cooking. Food is placed in a basket which is lowered into the pool for about 7 to 15 minutes, depending on what's being cooked. 

The geothermal footprint at Rotorua is extensive with hot springs occurring on both the northern and southern shores of Lake Rotorua. Whakarewarewa is situated on the southern shore and the hot water found here ranges from about 90 - 110C. The composition of the hydrothermal waters at Rotorua suggests that there are three related hydrothermal cells. Whakarewarewa and a hydrothermal system which surfaces beneath Lake Rotorua are the hottest reaching temperatures in excess of 250C, at depth. The water flowing to the north of the lake is cooler at 220C. Ions dissolved in the hydrothermal fluids suggest that they interact with basalt and/or rhyolite at depth with basalt being the probable heat source for the thermal waters (Giggenbach and Glover, 1992).

Cole, J.W. 1984. Taupo-Rotorua depression: an ensialic marginal basin of North Island, New Zealand. Geo. Sco. London, Special Pub. p 109-120.

Giggenbach, W.F.  and Glover, R.B. 1992. Tectonic regime and major processes governing the chemistry of water and gas discharges from the Rotorua Geothermal Field, New Zealand. Geothermics pp 121-140

Parekohuru, most of the hot water used at Whakarewarewa comes from this spring. It is also the cooking pot.
Pohutu, Big Splash, Geyser (I think)

Whakarewarewa Village with Rotorua in the background

Mud pool with gas bubbles. Photo by Julian Joyce.

The hangi meal, cooked with the wonders of geothermal energy :) and very tasty

Wednesday Rocks: #1

Wednesday rocks will be my regular mid-week post of a cool, in my opinion, geo-related photo with a bit of an explanation. 

Today's image is from the Cape Fold Belt (CFB), which is a mini meme started by Brian Romans of Clastic Detritus with posts by Evelyn Mervine of Georneys and Callan Bentley of Mountain Beltway

The CFB extends for roughly 500km from Port Elizabeth to Cape Town where it takes a 90 degree turn northwards and can be followed for about 350km to Vanrhynsdorp. From the air the rocks of the CFB form very distinctive ridges which I'd always watch out for when flying to Cape Town. I get bored during flights so seeing the familiar folds and ridges of the Cape Mountains is a nice reprieve from the monotony of the Karoo. There is a cool Landsat image of the CFB here posted by Jeanine Engelbrecht.

Near vertical bedding of the Carboniferous Witteberg Group. Mudstone layers
have been preferentially weathered leaving two sandstone ridges.
The photo is fom the hills behind Ladismith, Western Cape, South Africa

Learning Geology Online: Sifting The Fake From The Genuine

This may seem like a random topic. But I come from a education system where the academic year begins now or within the next month and with all the talk about the importance of lectures it seemed natural.

Many people are interested in how the Earth works. They have become interested in rocks by reading geology blogs, moving to areas with rocks visibly mangled by tectonic forces or hearing about volcanoes, earthquakes and climate change on the news. The information from blogs is like dipping one's toe in the water, mangled rocks are just plain confusing and the media often gets things wrong. People interested in Earth processes and geology may be left wanting more.

My sisters are studying by correspondence through the University of South Africa (UNISA). This has made me curious about this as an option for geology. Can one study geology by correspondence or online? The advantages of distance learning are; it is perfect for people who can only study part time and it tends to be cheaper than physically being on campus. On the other hand one has to be very self motivated and disciplined and there are no lectures or lecturers to guide one. Yes emails are answered but there is nothing quite like one on one contact when one is struggling with a concept. Added complications when studying geology by correspondence are field work and practicals. I have found that students struggle with concepts such as mineral cleavage or visualising things in 3D (yes the layers on Table Mountain do indeed go all the way through the mountain). My one sister did chemistry and zoology through UNISA (she's now studying psychology) so the practical side is not impossible. She did her chemistry practicals in the chemistry labs at the University of Namibia and the zoology practicals in Potchefstroom, South Africa. So I know that studying science via correspondence is doable. But are there options for people interested in geology? And if yes what are they? 

Table Mountain, Cape Town, South Africa. Taken from Lion's Head.

From my googling there seems to be two options 1) a degree in geology by distance learning and 2) free courses which teach the basic principles but do not result in a geology degree. I have also discovered that this is more complex than I had at first thought so I am going to cover distance learning in a series of blog posts. I shall evaluate the different free courses and then potential degree options by country. In this post I shall tackle how to choose an institution.

Important questions to ask yourself are: what do I expect to gain from this course/degree? Do I want to be a geologist or do I just want an introduction so that I understand the basics? If I want to be a geologist will this degree make me employable as a geologist? Is the organisation offering the course a real accredited institution?

The last two questions are linked. A degree from a genuine institution should make one employable as a geologist. Determining the legitimacy of an online institution can be easy in some cases and difficult in others. Courses from the Massachusetts Institute of Technology (MIT) or Birkbeck University of London are probably legit. Courses from University Degree Program are probably not. Personally I would use four steps to determine the legitimacy of an online university which I have listed below. If you can think of any of any others feel free to add them in the comments section.

1) Is the institution accredited by a valid organisation?

Wikipedia has a wonderful list of dodgy institutions (interestingly/unsurprisingly a fair number of them have theology in the title). Wikipedia also makes life easy by listing all the bodies which can legally decide whether an institution is accredited or not. Although the Central Council of Homoeopathy is on this list! To complement the list of accredited accreditors Wikipedia has a list of non-accredited accreditors.

While I have linked to Wikipedia here, remember the lists are probably incomplete so use them as a starting point for your search.

2) What is their course work/syllabus?

Courses about plate tectonics, mineralogy and petrology are a good start. Courses about Noah's Flood are an obvious red flag.

3) Check the staff.

Who works at the institution? Where did they get their degree from? What are their research interests? Have they published any journal articles? Which journals have they published in?

4) To make doubly sure you can check with on organisation you trust.

Geological surveys and societies are a good places to go. The Geological Society of London a list of accredited UK institutions, for example. If there is nothing on their website you can contact your local survey and ask them if the online institution you are thinking of enrolling with is valid.

Once you have determined that the institution is genuine the next step is looking at the courses offered in more detail. This will be the topic of my next post about online learning.

Windhoek's Weird Weather

Ron Schott is hosting the latest Accretionary Wedge. He is asking us to recall the most memorable/significant geologic event that we have directly experienced. I have lived my life in very geologically stable places so this topic may seem a bit odd as my first entry for the Accretionary Wedge. There has been some neo-tectonic activity with small earthquakes in Namibia and the Western Cape, South Africa, but I have not felt any. There was also apparently an earthquake near Cape Town in my first year at university. I didn't feel that one either. I have traipsed across active faults and volcanoes but fortunately non ruptured or erupted while I was there. The youngest volcano I've lived next to is Regenstein, on the outskirts of Windhoek, and that last erupted in the early tertiary (the only age I can find; Pirajno, 1994) and is extinct. When it comes to geologic hazards, I have lived a sheltered life.

My sister-in-common-law and her husband used to live in Christchurch. It was scary when we couldn't contact them during the 22-Feb-2011 earthquake. Fortunately they were ok, although, their office buildings have been either demolished or condemned. There was a slim chance that we would be spending this christmas in Christchurch. However, they moved the week before we arrived in New Zealand. They now live on the North Island and I am charged with keeping them abreast of volcanic developments. My Partner was in Christchurch for the boxing day earthquake 2010 and in Brisbane during the floods in January 2011 (he just missed the cyclone). Me? I was in nice, stable and politicians aside, non-crazy Southern Africa. Windhoek, Namibia to be precise. What could I possibly experience in Windhoek that would fit the guidelines of Accretionary Wedge #41?

Windhoek is supposed to have an average rainfall of about 350mm per year. Normally we are grateful for rain. We might even consider investigating the merits of rain-dancing. When Windhoek rivers flow many (most?) people in Windhoek go down to the banks to watch the standing waves go by and children play in the parts flowing slowly. Summer in Windhoek, you see, is usually hot and dry. 

The hills on the southern edge of Windhoek. December 2010

Not very green and not much grass to speak of. December 2010. Jill Russell
(aka Jilly Bean) smiling at the camera
In January last year it was different. Last year we had 383.6mm of rain in January alone. By the start of winter Windhoek had had over 1000ml of rain! By the start of winter we were all rather damp and sick of rain. Our roads were full of pot-holes and in some cases washed away all together. There are three bridges, I know of, across the Klein Windhoek River, Windhoek's main river. The roads the river crosses tend to be added to its sediment load.

This unusual rainfall occurred across the country. There was flooding in the North. The Sesriem Canyon was full of water and Sossusvlei was flooded in the South. I spent a weekend in Henties Bay. It rained on our first night. Henties Bay is in the desert. Rivers in Windhoek and across Namibia were still flowing in May. Unheard of! Then in winter it actually snowed. Just a dusting in Windhoek and a bit heavier in the South. It last snowed in Namibia in about 1995. 

Exactly the same slope as the first picture. January 2011

The hills on the southern edge of Windhoek, January 2011

And there you have it the most significant earth science related event I have experienced directly, to date. As for Windhoek? So far this summer has been business as usual, piping hot and dry, with all the people I know in Windhoek looking at the sky, searching for the welcome glint of a cloud.

Pirajno, F. 1994. Mineral resources of anorogenic alkaline complexes in Namibia: A review. Australian Journal of Earth Sciences, pp. 157-168.

More photos from Windoek. These are of Avis Dam on the eastern edge of the city.

Avis Dam flood plain, Windhoek, December 2010

Avis Dam flood plain, Windhoek, January 2011

Rail bridge, and river feeding Avis Dam. Windhoek, beginning of January
River flowing into Avis Dam. Windhoek, 22 January 2011