How flat is Australia?

We recently drove down the coast to Mackay, then inland and a lot further South to Carnarvon Gorge before returning home via Clermont and Charters Towers. I will write about Cape Hillsborough and the Gorge in due course but first I will share my overwhelming impression from the 1800 km, twenty hour, trip: it’s flat! Really, really, flat!

We have known for a long time that Australia is flat – old, worn down, eroded, etc – but there’s a difference between book-knowledge and body-knowledge.

Body-knowledge now tells me very clearly that you can drive for a couple of hours along the Bruce Highway from Townsville to Bowen without going higher than 20 or 30 metres above sea level except for a couple of bumps. When you get there, Bowen’s topography is like Townsville’s: flat and low-lying with a few big bumps in the distance. Most of the run from Bowen to the Cape Hillsborough turn-off is the same again: swamps, lagoons, floodways, and an average altitude of perhaps 20 metres.

Heading inland from Mackay towards Emerald there’s more flat coastal land, rather like the Burdekin irrigation area, before (wow!) hills. Up and up and … flat again. Not quite as flat, admittedly, but far from hilly. And the trip from Springsure to Charters Towers is flatter again: hundreds of kilometres with wide, level, horizons and altitudes varying not-at-all-wildly between 250 and 300 metres according to the car’s onboard map.

Porcupine Gorge region
Looking over the savannah from a low hill on the road from Hughenden to The Lynd – much like the landscape between Clermont and Charters Towers

Relief maps

All of which took me back to my childhood, sitting (somewhat bored) in a Victorian primary school classroom and contemplating the globe on the teacher’s desk. It might have been a 12 or 15 inch globe, and its surface was ridged with mountain ranges. Surely the Himalayas should be higher than that? Mount Everest was 29,000 ft high, I knew, and that was very high, wasn’t it?

So I did the sums: diameter of the earth = about 8000 miles, so the scale of the globe was 1 inch to so many miles, Everest was … five and a half miles high (oh! that’s not much compared to the size of the earth) so Everest at the scale of the globe should be … only about one thirtieth of an inch high! Barely detectable, in fact, and such a surprise that I’ve remembered it ever since.

To bring it up to date, one thirtieth of an inch is a little less than a millimetre and, since all the rest of the earth’s surface is much lower than the Himalayas, a relief globe which was truly to scale would be smooth to the touch.

A relief map of Australia

Which brings us back to Australia. Let’s make a relief map of this flat old land, in imagination at least.

It’s about 4000 km from East to West and 3200 from North to South. Let’s reduce that to one metre by 750 mm to be manageable but leave us plenty of room to work with, and let’s base it on this map from Geoscience Australia because it’s so clear and simple:

topographic map of Australia
Australia’s elevations

Here we go:

  • One table-top, blue for choice, for the sea we’re girt by.
  • One sheet of paper (a nice dusty peach colour) for all the land that’s less than 300 m above sea level. How thick? If 4000 km = 1000 mm, 300 m = 0.075 mm which turns out to be the thickness of the lightest copy paper (60 gsm rather than the standard 80 gsm) from our local supplier. Cut out the continent and Tasmania and spread them carefully on the table.
  • Two big cut-outs (a slightly darker brown) and a few smaller ones  for the land between 300 and 600 metres. How thick? 60 gsm again.
  • Eleven little cut-outs (a nice red-brown) for the land above 600 metres How thick? Let’s use 60 gsm again.
  • What about the mountains? Well, Kosciuszko is 2300 metres high and that reduces to 0.55 mm at the scale we’re using. Our three sheets of paper add up to 0.23 mm, so we only need another one-third of a millimetre. A sparse sprinkle of fine sand over the darkest of our three layers of paper would be about right for the highest mountains.

And we’re done.

That Great Dividing Range doesn’t look very high any more. You could drive clear across the continent from Brisbane to Shark Bay without going over 600 m, and come back from Port Hedland via Mt Isa to Rocky just as easily.

Even more impressively, you could go almost directly North-South, from the tip of Cape York to the point where the Vic-SA border touches the coast, without going over 300 metres. The high point of the trip would be the watershed which divides Gulf rivers from the Lake Eyre basin, somewhere near Hughenden.

Yes, it’s flat!

Where did we come from?

Where Did We Come From? is the title of a book written by Carl Zimmer in the wake of the discovery of the “hobbits” of Flores fifteen years ago. It was a very good popular introduction to human evolution.

According to Zimmer, our African ancestors parted company with the ancestors of chimpanzees and bonobos six or seven million years ago to begin developing an upright posture, tool use and, perhaps most importantly, language. Our own species, Homo sapiens, evolved about 200,000 years ago and began spreading out of Africa 130,000 years ago, through Europe, Asia, Australia and, eventually, America. We lived alongside closely related species until comparatively recent times. Neanderthals reached Europe before we did and coexisted with us there until 28,000 years ago, if not later. The ‘hobbits’ of Flores, by far the most spectacular recent discovery in the field, survived as recently as 18,000 years ago, well after Homo sapiens had migrated through South Asia and the islands to Australia.

Given the pace of discovery in the field, Zimmer’s book is now somewhat outdated. This collection of recent articles introduces research which adds depth and complexity to Zimmer’s account without changing its broad outlines. I have assembled them here in evolutionary order. Continue reading “Where did we come from?”

Winter Solstice

Midwinter, the winter solstice, doesn’t mean as much here in the tropics as it does further from the Equator but it’s still a significant turning point.

The winter solstice is always close to June 21 – 22, and this year’s was yesterday, June 21, according to this lovely site. (I chose it partly in memory of a warung (restaurant/cafe/bar) owner’s patient explanation of an amazingly detailed Hindu astrological calendar to me in Bali a year ago.)

According to this site, the solstice was not just generally “June 21” but specifically at 20:06:39. Sunrise was at 06:45:29 and Sunset at 17:43:38, for a Day Duration of 10 Hours 58 Mins 09 Secs. The previous day was 1 second longer and today was the same length as the solstice day.

Continue reading “Winter Solstice”

Winter is here

wattle in flower
Winter arrived yesterday, with its usual suddenness.

As in most years, a big weather pattern somewhere down South pushed cold, dry air from Central Australia out over the ranges to Townsville. Overnight temperatures dropped, and the humidity crashed. Last year I reckoned the Dry arrived at the end of April, as it did in 2014 and 2015 so we’re running a couple of weeks late this year.

In numbers, the changes are from overnight minimums of 18 – 21 C for the beginning of May down to 13.4 and 10.6 on the nights of the 12th and 13th, and humidity from 55 – 90% down to 16 – 19%.

In daily life that means the cat becomes a permanent lap-rug, if he can get away with it, but we’re not permitted to stroke him because sparks leap painfully from the tips of his ears and tail. Meanwhile, we search for windcheaters we haven’t worn for six months and seek out patches of sunshine in the morning instead of drifting automatically into shade.

Let me be clear, however: I am not complaining. I love this weather, and after a good Wet season I really look forward to it.

Bali Botanical Gardens

bali botanical garden
Formal gardens in the European style

The Bali Botanical Garden is up in the mountains, near Mount Batur, an hour or so from Ubud by car. Its altitude makes its climate significantly cooler than the lowlands and the day we visited was overcast with intermittent rain but we had a wonderful time anyway. The orchids and ferns were particularly good, and we would have spent far more time in the Taman Usada or Continue reading “Bali Botanical Gardens”