People are talking about tremors near Fraser Is causing this. One guy (on fb) explained it this way:

“Unlikely. There was a similar sand slump at Rainbow Beach in 2011. These slumps appear to be caused by liquefaction – water from the subsurface wells up and forces the sand grains apart, reducing the friction between the grains which keeps the sand in place. This then turns it into a slurry which slumps down into the ocean.

It is possible that tremors caused the water flow – but not likely given similar events in the past. Just a coincidence.”

So what happened?

kii said:

So what happened?

I don’t want to alarm people but perchance a judicious read of this link may bring some sense to what is going on:

http://www.theguardian.com/world/2015/sep/26/blood-moon-mormon-church-apocalypse-warning

Shoosh sibeen!

Neither MV nor his jackhammer have been sighted for some time..

I think the almighty tried to smite Lemon Tree Passage… and missed…

So, apart from MV and his jackhammer, the blood moon/end of the world….what the fuck happened?

kii said:

So, apart from MV and his jackhammer,

I don’t think you need to look any further.

have we reached peak sinkhole yet?

A tongue of land like that is particularly vulnerable to erosion, the effects of which can be quite sudden at times.

kii said:

People are talking about tremors near Fraser Is causing this. One guy (on fb) explained it this way:

“Unlikely. There was a similar sand slump at Rainbow Beach in 2011. These slumps appear to be caused by liquefaction – water from the subsurface wells up and forces the sand grains apart, reducing the friction between the grains which keeps the sand in place. This then turns it into a slurry which slumps down into the ocean.

It is possible that tremors caused the water flow – but not likely given similar events in the past. Just a coincidence.”

So what happened?

Something from outer space, looks like a UFO is still at the scene.

Bubblecar said:

A tongue of land like that is particularly vulnerable to erosion, the effects of which can be quite sudden at times.

Yes. It’s happened a few times in recent years.
But what happens? Also…why are people still camping there if this area is vulnerable ?

I wholeheartedly condone this effort of MV’s to run his own tunnel highway into brisbane. Very singleminded!!!

:P

diagram of sinkhole

A sinkhole is a Basin formed by continuous water infiltration into calcareous rock, causing the dissolution of the rock.

sinkholes are visible on the surface

when a sinkhole forms further down under the surface it is called a cave

I think

more information

https://americaninfomaps.wordpress.com/2015/03/18/sinkholes-and-karst-terrain-regions-in-america-1900-2015-maps-geological-data/

http://www.weatherwizkids.com/?page_id=1331

CrazyNeutrino said:

more information

https://americaninfomaps.wordpress.com/2015/03/18/sinkholes-and-karst-terrain-regions-in-america-1900-2015-maps-geological-data/

http://www.weatherwizkids.com/?page_id=1331

What are sinkholes?

Sinkholes are pits in the ground that form in areas where water gathers without external drainage. Sinkholes mainly occur as water drains below ground. It can dissolve subterranean caverns, particularly in areas where the bedrock is made of water-soluble evaporate rocks such as salt or gypsum or of carbonate rocks such as limestone or dolomite.
sinkhole

What causes sinkholes?

Sinkholes can be natural or man made. Natural sinkholes occur due to erosion or underground water. They start developing long time before it actually appears. The ground beneath our feet is not as much of a solid structure as we think it is. The ground is made from dirt, along with many rocks and minerals. There is water continually seeping in between the mud, rocks and minerals, as it makes its way down to the ground water reservoirs. As this happens, the water slowly erodes the rocks and minerals. Sometimes the flow of water increases to a point when it washes away the underground structure of the land. And when the structure becomes too weak to support the surface of the earth, it collapses and opens up a hole. This is how sinkholes are formed.

more..

The only time I visited Rainbow Beach the blue crabs (Soldier Crab, Mictyris longicarpus) on the beach were being decimated by each 4WD vehicle that drove along the beach, and tacks behind the beach were seriously dangerous to hikers for the same reason. Saw my first and only Common Keelback on one of those back tracks, was seriously concerned about its lifespan under those circumstances.

stumpy_seahorse said:

have we reached peak sinkhole yet?

Not in Florida.

> So what happened?

The normal method for sinkhole formation is collapse of an underground limestone cavern. I don’t know it that’s true in this case.

LOL a google search for “rainbow beach sinkhole cause” yielded as first entry “A major sinkhole near Queensland’s Rainbow Beach swallows …. Nicole Kidman’s last appearance on the London stage”.

rocks such as

salt rock

gypsum rock

carbonate rocks like

Limestone or

dolomite.

Have we heard from MV?

yep

Abseiling down a sinkhole?

Not sure what is going on here

I was in Brisbane when this happened, but we have made a quick trip to Rainbow Beach and back today, moving another load of stuff there. I just got back to Brisbane. I’m OK and our house is fine. This event was about 15 km north of our place, at a popular camping spot – Inskip. I didn’t go there and rubberneck the event, so my interpretation below is based on looking at photos on news sites and a knowledge of the geology and geomorphology of the area.

I think it was a slump not a sinkhole. A sinkhole technically (as pointed out earlier) is a Karst landscape feature, formed by the chemical erosion of underlying limestones or other soluble rock.

Inskip is located on the sand bar defining the outer limit of the above-water section of the Mary River delta. The sand bar comprises fine grained, dominantly quartz sand, which is entirely unlithified – it is not rock.

Where the event occurred, the sand bar is a couple of hundred metres wide, and is at maximum about 3 metres above high tide level. The slump is on the ocean-side of the sand bar. My guess is that what happened is the inverse of the “straw that broke the camel’s back”. Ocean erosion removed the last grain of sand holding that bit of the bar up, and it slumped into the ocean.

stops pacing up & down

party_pants said:

stops pacing up & down

Here, have a Guinness to calm your shattered nerves.

Michael V said:

party_pants said:

stops pacing up & down

Here, have a Guinness to calm your shattered nerves.

Cheers mate!

The slump is shown clearly on this photo taken from the air. The image looks west from the ocean, across the Inskip sand bar to the Mary River inlet.

I wonder if it would be a good fishing spot. Looks deep…

Michael V said:

The slump is shown clearly on this photo taken from the air. The image looks west from the ocean, across the Inskip sand bar to the Mary River inlet.

!https://scontent-hkg3-1.xx.fbcdn.net/hphotos-xft1/v/t1.0-9/12038041_825491530902690_2364778265617354756_n.jpg?oh=8de3ba1827a9872c997f837a9c2562bc&oe=569AA1C6

Looks reasonably deep.

party_pants said:

I wonder if it would be a good fishing spot. Looks deep…

I reckon it could be for a few weeks at least – until it fills back in. But then most people camping there are there for the fishing, so I doubt (with my level of fishing competency) I’ll get a look in…

Oh, and I should add that the earthquakes we had a few weeks back (last was16 September, M3.3) likely had nothing to do with triggering this slump .

Earthquake-triggered liquefaction occurs at the time of the earthquake, and pretty much finishes when the shaking stops.

Thanks for the responses, MV (and some others)

I figured some of this out. I can’t get over the fact that similar events have occurred in the same area and people are still allowed to camp there. Wouldn’t these previous incidents indicate that it’s a fairly fragile/unstable structure and maybe people need to stay off that point?

Oh well, it’s only Queenslanders and a few Yanks that might drown in the ocean, get eaten by sharks….that sort of thing.

Thanks MV.

I feel bad for the site owners, they’ve lost most of their camping ground and scared off customers in the middle of school holidays.

Sinkhole sounds more mysterious than slump so I expect the media to stick with sinkhole no matter what.

Divine Angel said:

Thanks MV.

I feel bad for the site owners, they’ve lost most of their camping ground and scared off customers in the middle of school holidays.

i think they’ll be fine… Melbourne’s been a sinkhole for years and people still go there…

Divine Angel said:

Thanks MV.

I feel bad for the site owners, they’ve lost most of their camping ground and scared off customers in the middle of school holidays.

It’s a National Park. We all own the site.

:)

Peak Warming Man said:

Sinkhole sounds more mysterious than slump so I expect the media to stick with sinkhole no matter what.

:)

Oh.

Well then I’m outraged that property I partly own hasn’t been concreted in place to prevent events like this.

Divine Angel said:

Oh.

Well then I’m outraged that property I partly own hasn’t been concreted in place to prevent events like this.

Heh! :)

http://www.abc.net.au/news/2015-09-28/sinkhole-at-inskip-geotechnical-engineers-to-use-radar-to-assess/6808590

The geotechnical engineer reports it to be a slump. Yet the journalist has included a side box explaining what a sinkhole is, referring to limestone dissolution etc. It is sand there, not limestone. As far as I am aware, there is no limestone within this sedimentary package. (sigh)

Michael V said:

I was in Brisbane when this happened, but we have made a quick trip to Rainbow Beach and back today, moving another load of stuff there. I just got back to Brisbane. I’m OK and our house is fine. This event was about 15 km north of our place, at a popular camping spot – Inskip. I didn’t go there and rubberneck the event, so my interpretation below is based on looking at photos on news sites and a knowledge of the geology and geomorphology of the area.

I think it was a slump not a sinkhole. A sinkhole technically (as pointed out earlier) is a Karst landscape feature, formed by the chemical erosion of underlying limestones or other soluble rock.

Inskip is located on the sand bar defining the outer limit of the above-water section of the Mary River delta. The sand bar comprises fine grained, dominantly quartz sand, which is entirely unlithified – it is not rock.

Where the event occurred, the sand bar is a couple of hundred metres wide, and is at maximum about 3 metres above high tide level. The slump is on the ocean-side of the sand bar. My guess is that what happened is the inverse of the “straw that broke the camel’s back”. Ocean erosion removed the last grain of sand holding that bit of the bar up, and it slumped into the ocean.

^
this

there is a lot of sand movement in and around this area

Inskip sinkhole: Possible ‘near-shore landslide’ at beach campground ‘relatively stable’, engineer says

A Queensland Government geotechnical engineer today said that the event may have been a “near-shore landslide” rather than a sinkhole.

sinkhole

slump

landslide

?

CrazyNeutrino said:

Inskip sinkhole: Possible ‘near-shore landslide’ at beach campground ‘relatively stable’, engineer says

A Queensland Government geotechnical engineer today said that the event may have been a “near-shore landslide” rather than a sinkhole.

sinkhole

slump

landslide

?

that’s essentially what a slump is… it seems to be to have all the characteristics of a typical circular slope failure

diddly-squat said:

CrazyNeutrino said:

Inskip sinkhole: Possible ‘near-shore landslide’ at beach campground ‘relatively stable’, engineer says

A Queensland Government geotechnical engineer today said that the event may have been a “near-shore landslide” rather than a sinkhole.

sinkhole

slump

landslide

?

that’s essentially what a slump is… it seems to be to have all the characteristics of a typical circular slope failure

Ok

If a slump, then there ought to be a sketch of it in my copy of “Capper and Cassie, Mechanics of Engineering Soils”. I’ll see if I can find a sketch on the web.

Something like this.