Tuesday, May 31, 2011

Tnorala - recreate the deep impact on your laptop!

An artist's impression... fortunately.
 If you're looking for an interesting way to try and grasp the vastness of geological time and the immensity of cosmic forces that have shaped our little planet, here's something that may be of interest.

Purdue University in Indiana USA, hosts this website http://impact.ese.ic.ac.uk/ImpactEffects/ called Earth Impact Effects. Colloquially it is known as the Catastrophe Calculator. This is great fun for the cosmically curious.

By putting in a variety of parameters like the size of the asteroid, the velocity and composition, the website will generate a complete description of the expected destruction from the impact. You also insert the distance you are observing the hypothetical event from, and the report will tell you what to expect.

As soon as we discovered this in the Land for Wildlife office, the race was on to recreate as closely as possible a modern day incidence of the impact that created Tnorala (Gosse Bluff) 159kms west of Alice Springs.

Using Google Earth and information on the nature of the projectile from the NT Government website, this is what the website gave us;

Your Inputs:

Distance from Impact: 159.00 km ( = 98.70 miles )
Projectile diameter: 600.00 meters ( = 1970.00 feet )
Projectile Density: 1000 kg/m3
Impact Velocity: 30.00 km per second ( = 18.60 miles per second )
Impact Angle: 45 degrees
Target Density: 2500 kg/m3
Target Type: Sedimentary Rock


Energy before atmospheric entry: 5.09 x 1019 Joules = 1.22 x 104 MegaTons TNT
The average interval between impacts of this size somewhere on Earth during the last 4 billion years is 1.5 x 105years

Major Global Changes:

The Earth is not strongly disturbed by the impact and loses negligible mass.
The impact does not make a noticeable change in the tilt of Earth's axis (< 5 hundreths of a degree).
The impact does not shift the Earth's orbit noticeably.

Atmospheric Entry:

The projectile begins to breakup at an altitude of 89700 meters = 294000 ft
The projectile reaches the ground in a broken condition. The mass of projectile strikes the surface at velocity 28 km/s = 17.4 miles/s
The impact energy is 4.44 x 1019 Joules = 1.06 x 104MegaTons.
The broken projectile fragments strike the ground in an ellipse of dimension 1.66 km by 1.17 km

Crater Dimensions:

What does this mean?
Crater shape is normal in spite of atmospheric crushing; fragments are not significantly dispersed.
Transient Crater Diameter: 6.14 km ( = 3.81 miles )
Transient Crater Depth: 2.17 km ( = 1.35 miles )
Final Crater Diameter: 7.81 km ( = 4.85 miles )
Final Crater Depth: 549 meters ( = 1800 feet )
The crater formed is a complex crater.
The volume of the target melted or vaporized is 0.279 km3 = 0.0671 miles3
Roughly half the melt remains in the crater, where its average thickness is 9.45 meters ( = 31 feet ).

Thermal Radiation:

What does this mean?
Time for maximum radiation: 253 milliseconds after impact
Visible fireball radius: 5.1 km ( = 3.17 miles )
The fireball appears 7.29 times larger than the sun
Thermal Exposure: 5.44 x 105 Joules/m2
Duration of Irradiation: 1.53 minutes
Radiant flux (relative to the sun): 5.91

Seismic Effects:

What does this mean? The major seismic shaking will arrive approximately 31.8 seconds after impact.
Richter Scale Magnitude: 7.3
Mercalli Scale Intensity at a distance of 159 km:
    VI. Felt by all, many frightened. Some heavy furniture moved; a few instances of fallen plaster. Damage slight. VII. Damage negligible in buildings of good design and construction; slight to moderate in well-built ordinary structures; considerable damage in poorly built or badly designed structures; some chimneys broken.


What does this mean? The ejecta will arrive approximately 3.05 minutes after the impact.
At your position there is a fine dusting of ejecta with occasional larger fragments
Average Ejecta Thickness: 3.15 mm ( = 1.24 tenths of an inch )
Mean Fragment Diameter: 1.43 cm ( = 0.564 inches )

Air Blast:

What does this mean? The air blast will arrive approximately 8.03 minutes after impact.
Peak Overpressure: 14400 Pa = 0.144 bars = 2.04 psi
Max wind velocity: 32 m/s = 71.6 mph
Sound Intensity: 83 dB (Loud as heavy traffic)
Damage Description:
    Glass windows will shatter.
    So there you go. A lot of technical stuff there if you're good at maths, but it seems that in the unlikely event that the Tnorala impact happens again in exactly the same place, all we need worry about is some shattered windows and a light dusting of comet fragments!
    Now if you liked that, you can go and try the visual version for a more updated version with some fancy graphics. 

    Wednesday, May 25, 2011

    Beware of rodent poisons - they don't just work on mice!

    Mice are very common at the moment and poisoning might seem an effective way to control their numbers. Due to environmental side-effects from poisons however, mechanical traps are an overwhelmingly preferable solution. While a mouse-trap may occasionally catch a wayward dunnart or native mouse, the larger scale effects of poisons entering the food chain are a much greater concern.

    The most common active agent in commercial rodent poisons is an anti-coagulant chemical named brodifacoum. In short - if you own rodent poison, you probably own brodifacoum. It is sold under many brand names including; Biosnap, d-Con, Finale, Fologorat, Havoc, Jaguar, Klerat, Matikus, Mouser, Pestanal (Sigma-Aldrich BT), Pestoff, Ratak+, Rodend, Ratsak, Talon, Volak, Vertox and Volid.

    Brodifacoum is an anti-coagulant which causes internal bleeding and may eventually cause death. It may be circulated or stored for up to 4 weeks in the fatty tissues and some organs, particularly the liver, and will be transferred to any animal which ingests the poisoned carcasses. While brodifacoum has not been shown to enter plants, it will remain in dry soil for several days after contact. Rabbits and native mammals may also be tempted by poison baits. Predatory and scavenging animals such as birds of prey, tawny frogmouths, fish and some small mammals may be adversely affected by the presence of this chemical in the food chain if they consume enough of animals that have died from anticoagulants. 

    A raptor would require the livers from at least 12 to 20 house mice carcasses for it to become a victim as well. Less obvious however is the impact of sub-lethal doses where predatory animals become impaired by the toxin.

    A Land for Wildlife member rescued a tawny frogmouth this week on a traffic island near Billy Goat Hill. The vet's explanation for its stupefied state? Poisoned mice. On the domestic front, vets have documented cases of pet dogs and cats being poisoned after eating rabbits, birds and mice that died from household baits.

    So if you are keen on keeping the mice away from your place, please stay away from the poisons and use the good old mechanical spring traps, or some of the inventive pit traps which only trap and don't drown the trappee. We don't need those extra toxins entering the food chain.

    On another note, as well as feral mice there are many native rodents and marsupials present around Alice Springs at the moment. It's an exciting time for wildlife lovers. Many of these species have not been recorded around Alice Springs for years and in some cases decades. Some of the species that have already been collected from Land for Wildlife properties include Long-haired Rat, Kultarr, Wongai Ningaui, and a number of species of Dunnart and Hopping Mouse. These are all of scientific and conservation interest as range extensions or little-known species.

    If you find any dead, small mammals which you can’t positively identify as a feral mouse please place it in a plastic bag and store it in a freezer. Contact the Land for Wildlife coordinators and drop the specimen in, or they will collect it for identification and examination. lfw@lowecol.com.au

    You never know - Alice Springs Mouse which hasn't been recorded alive in central Australia since two centuries ago!

    Sunday, May 22, 2011

    World Turtle Day - Centralian Style...

    OK... so it's not the best turtle sand sculpture ever, but we're relying on points for effort and originality as dry desert sand just doesn't cut it for sculpting and this may be the only entrant in the competition made from a sand dune in the centre of the continent.
    From a certain angle it really did look like a turtle... honestly... perhaps if you squint really hard..
    Well, perhaps it is the worst sand sculpture turtle ever, but hopefully it's the thought that counts and it was all for a good cause. We've sent a message of support for the declaration of marine reserves across our northern coasts.

    From left: Land for Wildlife Coordinators, Jesse Carpenter and Chris Watson, LES Consultant Holga Woyt. Photographer - Emily Bynon and not in the picture is Bingo the dog.
     4 people and an amused dog spent an afternoon trying to turn red sand into a green turtle and if that isn't worth a Wilderness Society T-shirt then I don't know what is!

    Friday, May 20, 2011

    Australia - The World of Parrots

    The newly released work by Canadian filmaker, Donald Kimball.
    Anyone who lives in Australia will be well aware of the richness of our birdlife, and particularly the parrots. Perhaps it is something that some of us take for granted, but to have birds as colourful and brash as Galahs, Ringnecks, and Budgies, bashing around in our backyards is unusual by world standards. It's an absolute delight for foreign visitors to land at any of our capital cities and find trees festooned with birds as dazzling as Rainbow Lorikeets, Crimson Rosellas, or Yellow-tailed Black Cockatoos.

    This is certainly something that had an impact on Canadian filmaker, Donald Kimball. A frequent visitor to Australia, and repeat visitor to Alice Springs, he was so taken with our parrots that he was driven to set himself a natural history filmaking task of Everest proportions - to film every living Australian parrot species in the wild. After 6 months, and inumerable thousands of kilometres travelling to every corner of the country, Donald has triumphed and we can finally enjoy the fruits of his adventure in the 4 disc DVD series he has just released, "Discovering the World of Parrots: Australia".

    Donald only dipped out on one species, the ever elusive Night Parrot. If he'd managed to film that bird it would have been front page news worldwide. There are no photos in existence of a live specimen and only a handful of people still alive who claim to have seen the bird in the wild. This obvious and forgiveable miss aside, the series constitutes a comprehensive catalogue of the most arresting members of the Australian avifauna.

    Some of the most stunning varieties are from the desert landscapes around The Red Centre so keep your eyes peeled for familiar settings.

    The DVD's are available along with several free trailers at Donald's website;

    World Turtle Day

    Australian Snake-necked Turtle, Chelodina longicollis. Thomas Ruedas, wikicommons.
    G'day wildlife lovers. There are a couple of important dates coming up this week. Sunday the 22nd of May is World Biological Diversity Day, surely a worthwhile observance for us all. This day was declared by the United Nations Convention on Biological Diversity and would seem to have plenty of media clout behind it.

    Another day which is perhaps less well known and certainly overlooked by those of us in Central Australia is Monday the 23rd of May - World Turtle Day! This day was actually declared back in 1990 by a mob called American Tortoise Rescue, but it has since caught on and spread well beyond the rescue of land tortoises in the continental US. What has all this got to do with us here in The Centre you ask?

    Well perhaps not much on the surface of things. If you dig a little deeper though, you will realise that we have some 18 species of threatened or endangered freshwater turtle species here in the Northern Territory according to the IUCN classifications. This doesn't even count all the endangered sea turtle species that visit our northern coasts through the year, all of which are suffering from the reduction of critical breeding grounds year after year.

    You may not think that there is much to be done about this from down in Alice Springs where we don't even get any turtles - but think again. On Sunday the 22nd of May (the day before World Turtle Day) people will be gathering all around Australia to build sand effigies of their favourite turtles to send a message of support for marine reserves in northern Australia to Environment Minister Tony Burke.

    The one thing we have lots of here in Alice is sand! So grab your bucket, grab your spade and head down to your nearest river bed or sand dune. Email the photos of your wonderful creations in support of an issue farther afield from The Red Centre. What better way to show the country what an enlightened, ecologically attuned community we are? Who could argue with a beautiful red sand sculpture of a Mary River Turtle?

    Email your photographs to  jenita.enevoldsen@wilderness.org.au and the best efforts will win a Wilderness Society gift pack. They're not expecting sand sculptures from the desert so any Red Centre entries will surely be well-received.

    Additionally, you can post your photos to the facebook page of the Australian Marine Conservation Society and also be in the running for prizes. For details check their World Turtle Day website at;

    For more information visit the Wilderness Society's World Turtle Day page: http://www.wilderness.org.au/articles/world-turtle-day-2011

    The Convention on Biological Diversity Page : http://www.cbd.int/idb/

    American Tortoise Rescue: http://www.tortoise.com/

    Thursday, May 19, 2011

    Land for Wildlife Members Devise Ingenious Use for Buffel Grass

    The Buffel Bridge
    Land for Wildlife members on the far side of Roe Creek have devised a brilliant way of putting removed Buffel Grass to good use - build a bridge!

    As Roe Creek has been flowing quite well in recent months, the sand has softened and is proving to be something of a barrier to 2WD visits to their property. After some long sessions of dedicated Buffel Grass removal it was decided that the weed might have another, more practical use. By laying the grass across the river and packing it down with a few trips back and forth in the 4WD it has rendered the creek navigable by most vehicles without the need to engage 4WD.

    Top work folks!

    Tuesday, May 17, 2011

    Fire Season Approaches with the Cooler Weather

    A fire front spreading out across the Wakaya Desert in April
    By now we are all fully aware of the extraordinary rainfall that The Centre has experienced this year. Along with this, the undergrowth has thickened up and is now beginning to dry out. All of this has firefighters up and down the territory bracing for a record year of fires, particularly here in The Centre. Already there have been a few outbreaks of fire up around Tennant Creek and closer to Alice around Aileron Station.

    If you have a property with heavy growth of Buffel Grass and other fire favourites then now is a good time to be thinking of putting in or maintaining fire breaks. To stand a chance of being effective, these need to be at least 4 metres wide and slashed down to a height of 250mm.

    There is more information on fire awareness in your Land for Wildlife property assessment report, but you should already have devised a viable fire action plan for your property. People often underestimate the impact a fire might have on their property so it is good to avoid an unpleasant surprise and make sure you are prepared in case conditions change suddenly.

    For more information on making sure your property is fire-ready, check some of the factsheets on the Land for Wildlife website at http://www.lowecol.com.au/