If this story is really 3 years old, I bet you Media Watch will give it some air time.
Haha, Media Watch will also be having fun with tonights episode of 7's Today Tonight.
There was a story about scammers and they mentioned someone had been ripped off $592,000 and then mentioned they were ripped a further half a million for a total of $1.92 million....... some good adding up right there.
Haha, Media Watch will also be having fun with tonights episode of 7's Today Tonight.
There was a story about scammers and they mentioned someone had been ripped off $592,000 and then mentioned they were ripped a further half a million for a total of $1.92 million....... some good adding up right there.
Easy answer to that one...they're journalists. How many of them actually know anything about science or maths. Very few.
Saw this happen to a car in Kal back in the early 90's. There was a huge storm and this caused one of the many old mine shafts dug underneath the town to collapse. There was a big hole where the car used to be . Never felt too safe driving around the place after that.
I lived in Kal as a kid.... no surprise my parents lived in fear that my brother and I would disappear down a hole one day.
The bush(where my bro and I used to go play) around Kal is like swiss cheese.
This is a geological condition also known as swisscheesiatis.
Not far wrong!
Alot to the Central American ismuth is made of limestone. These storms have carved out enormous amounts of the substrait. These sinkholes are very common. If you look at a map of these countries, they have very few rivers. Most of the water flows into these sinkholes and out to sea. There have been a few adventurers that have followed these underwater rivers all the way out to the Gulf of Mexico and the Pacific too. The flow of this freshwater being strong enough to remain drinkable to a couple of km from shore, even producing a two level water system with the fresh water running below the saltwater, even though the salt water is denser.
This explains why you don't see the bottom of the hole- it isn't there in the first place!
The ancient Aztec civilization which had suddenly disappeared hundreds of years before the Maya, and Columbus, fell victim to this geology, where their entire aquaculture revolved around this underground water system. That was until erosion undercut their water source and instantly killed their civilization.
The more recent Maya civilization, and Mexico City now too, relies on much of this underground water source. Problem for them is that they are using it faster than it is being replenished, AND it is seasonal- It's the tropics there.
The bottom of the sinkhole is the channel that carries the subterranian water. So as such the sinkhole doesn't have a bottom as it was washed away.
These sinkholes occur initally through a fissure in the rock, creating a gutter which leads to the subterranian 'river'. Over time the fissure spreads the water through the rock through capillary action. This widens the weakening effect of the errosion, until the weight of the material above the 'gutter' causes the weakened erroded rock to cave in.
There is such a sinkhole here in New South Wales at the Abercrombie Caves, not far from Cowra. I was there 18 months ago too. To access the main cave there you actually walk down into the sinkhole. A massive structure. The main cave is the subterranian river that still contains its original river run, but obviously without the amount of water that originally created it.
Actually, our Abercrombie caves show that the local geology has undergone many climatic changes. First a marine enviroment to create the coral reef, metamorphosing into limestone. Geological movement lifted the reef and a tropical enviroment erroded the limestone and created the sinkhole and cave system. Now the area is much drier, with a very different climate and flora, limestone errosion occuring much more slowly.
The river running through the cave system does on occasion experience flooding, evidenced by the debri of trees and rubble that the force of water washes down the near dry riverbed.
Looking at the sinkhole I'm struck by just how circular it is. I think other sinkholes I've seen have also been round (there's a nice one south of Braidwood).
Now the underground cavern is long and sinous and the fissures through the rock are almost certainly not straight and vertical. So why does the rock failure have such a regular shape? Why isn't it elongated and irregular? The answer is obviously more in physics and engineering rather than earth science.
Last edited by AstralTraveller; 03-06-2010 at 07:16 PM.
Reason: typo
. Never felt too safe driving around the place after that
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