Tuesday 24 June 2014

Earth Learning Idea

I have recently come across an interesting and easy to understand site that explains earth processes in fun and creative ways. This is a site called Earth Learning Idea. By way of examples here is a demonstration of sink holes that you can try yourself (just like those I mention in the addendum to this earlier blog post):

I'm pleased to see such an interesting site. It made me wonder whether I should be more pro-active in earth science education. Recently helping to sort out a rock collection for a local environmental centre is something that I enjoyed. I've also been honoured by an invitation to do a formal presentation at this years Big Scrub Rainforest Day. I'm happy to do these things because I enjoy geology and I enjoy talking with people.

Interestingly, as a member of the Geological Society of Australia I can be more formally aligned with geology education by joining the Specialist Group in Geological Education. I just don't want to stretch myself too far as I'm already a member of three specialist groups: the Environmental Engineering and Hydrogeology Specialist Group, Specialist Group in Geochemisty, Mineralogy and Petrology and the Specialist Group in Vocanology (Learned Australasian Volcanology Association). I have another 6 months to decide... I think it is good to take time in making decision... even if this is a little one.

Saturday 7 June 2014

Blog Update #5

It has been about a year since my last blog update. I'm pleased with how well the blog is ticking along though I've been a bit slow in posting sometimes and I am still neglecting many areas. The area between Camden Haven and Coffs Harbour is regularly neglected, so too the New England highlands. I also tend to leave at least one typo per post! Not for the first time I will try and remedy these issues in future posts.

The next few months will have a focus on several areas:

  • Continuing on the hydrogeology theme;
  • Points of interest in the Macleay River catchment;
  • The Mount Warning Central Complex;
  • Recent reviews of the upper stratigraphy of the Clarence-Moreton Basin;
  • Some more posts on gas resources; and
  • A granite intrusion or two in the New England tablelands

While I'm looking both backward and forward. I'm looking forward to reaching 100 000 page views in the next few months. At the time of this post there were over 85 000 views though I estimate approximately 20% of these are not human visitors.

I'm also looking forward to the pocket money this blog is now helping me with. Visitors will notice advertising in the top right corner of the page. When visitors click on these ads I receive between 1cent and 80cents from Google. These ads are not ones that I choose but are placed by Google Adsense based upon the content of this page and your own Google search history. So far I've noticed ads for fracking companies, TAFE and universities and even Clive Palmers Australia Party! I've had advertising for about 2 months now and I've made enough for about 4 cups of coffee. How exciting!

Thanks to everyone for continuing to visit and comment. I appreciate comments and try to respond to all of them.

Sunday 1 June 2014

This is what one aquifer looks like

In some amazing places you can immerse yourself in an aquifer. These places are rare and dominated by a rock type that does not occur in any substantial amounts in our region. However, people dive in the sub-terrainian waters of the limestone caves of the Nullabour in South Australia. The best aquifers in our region do not contain large caves compared with limestone areas. They are hosted in riverine alluvial sediments, fossil soil horizons in volcanic rocks, or fractures in hard metamorphic and volcanic environments. The main aquifers being on the coastal river flood plains, Alstonville Basalt and the New England areas respectively. However, volumetrically the sources that are very large are those in coastal sands.

Auger containing saturated sand from the Woodburn Sands
This post is an illustration of how one of those coastal sands aquifers looks. I've covered the Woodburn Sands in several previous posts but a quick summary is still needed. The Woodburn Sands are beach and dune sand that was laid down during the last significant interglacial. This was around 130 000 years ago during the Pleistocene period. The sea level was much higher than now and this meant that beach systems were often formed a significant way inland.

From the picture you can actually see what the medium that hosts an aquifer looks like. The Woodburn Sands are just that, sands. The sand grains are mostly quartz but there are also some grains made from volcanic and metamorphic rock fragments. Occasionally you can see grains of heavier minerals that were mined until the 1980's. The sand grains are very similar in size which is typical of wave and wind sorting. There is a very small fine fraction of clayey material.

Where the clay content is higher the ability of the water to flow through the aquifer is reduced. This is why some bores can only produce a small amount of water compared to the huge volume that is in the whole aquifer. This is an example of why aquifers tend not to behave as underground lakes. You can pump water out of one end and run out because the hydraulic conductivity (flow velocity) is not high enough to allow the water at the other end of the aquifer to flow in.

The Woodburn Sands is not the only important coastal sands aquifer in the region. Another very important water source include the Macleay sand coastal aquifers. These aquifers were formed in a similar way to the Woodburn Sands and are used for similar purposes. Usage includes irrigation, stock, domestic use and town water supply for places such as Kempsey and Evans Head. There are also some interesting arsenic contamination issues in one aquifer system (Stuarts Point) in the Macleay area which I will post on in the near future.

The similar characteristics of the coastal sands aquifer systems in the North Coast area has motivated the NSW state government to develop a Water Sharing Plan for these systems as a whole. The Water Sharing Plan is expected to be formally adopted this year (2014). Local governments regard groundwater from the coastal sands aquifers as very important. Rous Water has recently adopted its future water strategy which identifies coastal sands as the main source of additional information in the medium to long term and Mid-coast water have recently increased their production of groundwater for drinking too.

Available here is a presentation by the NSW Office of Water on the overall coastal sands systems in North East New South Wales