Category Archives: Earth

Sydney Climate Update

We’re just coming out of what felt like a freezing cold winter, it seemed like it was bitter and dark for so long. But when it comes to accuracy human skin and brain cells are really terrible at remembering and comparing the weather. Lucky for us we have the data!

Cold and wet at the Mt Tomah botanical gardens

The BOM have updated their long term climate data again. This time we’re in for a treat, we have updates to temperature, sea level and rainfall.

Looking at the maximum and minimum monthly temperature averages we have indeed had some cold months. The July average minimum of 8C is the coldest since 2002 when it was 7.9C, and looking back 30 years only 1995 was colder. The mean maximum for July was cool but many years have been cooler over the past 30 years. 2013 and 2014 were quite warm by comparison though, maybe that’s why it felt cold this year. As we’ve only got up to July we can’t compare moving averages yet.

For sea levels the short term averages actually show a drop in 2014. The 5yr and above moving averages still show an unmistakable upward trend.

Rainfall averages are up, I don’t recall it being particularly wet though, so much for memory.

Climate data update

I’ve updated the Sydney temperature and rainfall pages with the latest data from the BOM, we’re pretty much right up to date now, thanks BOM. Something has happened to their sea level pages though, their Fort Denison measurements have not been updated since the end of 2012.

It’s the long term trends that are of most interest so nothing mind blowing in these updates, temperature continues to rise on almost all average time periods. I found it interesting that even after the “August of rain” most rainfall averages are still low when you look back over time.


The 2014 Annular Solar Eclipse

The 2014 annular solar eclipse was meant to be a rare one, occurring once every 73 years. It was going to be about 50% in Sydney, not total but still impressive to watch. I left the arc welding helmet at home with instructions for the kids on how and when to use it to look at the sun. The goggles came with me to work.

It was clear all day, but the clouds gathered near the horizon just as the sun dipped and the eclipse was due to start.


The 2014 Annular Solar eclipse as viewed from Sydney. Just clouds.
Vikram and I climbed to the carpark roof to view the eclipse, but it was behind the clouds.

Igneous Dyke near Brooklyn

An igneous dyke is where molten magma has forced it’s way up into a crack between existing rocks. Dykes can extend for many kilometers in lines on the surface.  There’s a dyke marked on the Sydney 1:250,000 geological sheet that cuts across the M1 and old pacific highway just south of the Hawkesbury River. It’s mentioned in the “Geology along state highways” section of The Field Geology of NSW. I’ve tried to spot it many times while driving down the M1, I think I’ve seen it but it wizes by so fast it’s hard to be sure.

The dyke is the red line striking ESE just south of the Hawkesbury River. Tv stands for Tertiary volcanics, which means the dyke is less than 65 Million years old. Geologically it’s a baby!

Last weekend I went for a ride down the old Pacific Highway and I’m pretty sure I found it.

Pacific Hwy Dyke
Dyke in a cutting beside the old Pacific Highway just south of the Hawkesbury River

It’s a vertical channel about 4m wide that cuts through the surrounding Hawkesbury sandstone. The material in the dyke was heavily weathered and seems softer than the surrounding sandstone.