Floating Rock Raft: New Zealand Questions Answered

In summary: I can't even read off the calculator hahacan someone tell me what that number is please, and then I'll work through the rest of the calculations, thanksIn summary, a newly discovered floating rock raft off the coast of New Zealand has a total estimated mass of 13 billion cubic meters, with an average thickness of 0.5 meters. This amounts to approximately 3.25 trillion kilograms of pumice rock. The exact destination or dispersal of the raft
  • #1
pnmeadowcroft
25
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Can anyone answer a couple of questions about the new floating rock raft off New Zealand ?

How much mass does it contain ?

Where is it headed ? ( or will it disperse ? )
 
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  • #2
pnmeadowcroft said:
Can anyone answer a couple of questions about the new floating rock raft off New Zealand ?

How much mass does it contain ?

Where is it headed ? ( or will it disperse ? )
Please post a link, do not make members hunt for the source.
 
  • #3
It has just been discovered around 09 August and there have been not published estimates of its total mass, as far as I know.

http://www.bbc.co.uk/news/science-environment-19207810
http://news.yahoo.com/bizarre-rock-ice-shelf-found-pacific-104349304.html

.
 
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  • #4
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  • #5
pnmeadowcroft said:
Can anyone answer a couple of questions about the new floating rock raft off New Zealand ?

How much mass does it contain ?

Where is it headed ? ( or will it disperse ? )

well time for you to try some maths ;)
you have some of the info, and wiki will provide the rest

its 26,000 sqr km x ~ 600mm (0.6metre thick)

wiki gives an example of ~ 0.25 g / cubic cm for pumice

work out the volume from the first 2 measurements then multiply it by the density

watch your values I would suggest get everything into cubic metres rather than trying to work with km, cm etc


Dave
 
  • #7
pnmeadowcroft said:
Yeah, 3.9 billion tonnes, but I don't really like that answer much. The picture on this page:

http://en.mercopress.com/2012/08/10/volcanic-pumice-mass-size-of-belgium-floating-off-the-coast-of-new-zealand

shows that the depth is far from uniform.

yup some bad maths there I think ;)

26,000 sqr km = 26,000,000 sqr metres ( 26 million) x 0.6 metres = 15,600,000 (15.6 million) cubic metres

0.25g / 1ccm => 2.5g / 10 ccm => 25g / 100ccm (ccm = cubic cm) 100ccm = 1 cubic metre

25g = 0.025kg

15,600,000 cubic metres x 0.025kg = 390,000 kg = 390 tonnes ( 1 Tonne = 1000kg)

some one check my maths please :)

Dave
 
  • #8
davenn said:
yup some bad maths there I think ;)

26,000 sqr km = 26,000,000 sqr metres ( 26 million) x 0.6 metres = 15,600,000 (15.6 million) cubic metres

0.25g / 1ccm => 2.5g / 10 ccm => 25g / 100ccm (ccm = cubic cm) 100ccm = 1 cubic metre

25g = 0.025kg

15,600,000 cubic metres x 0.025kg = 390,000 kg = 390 tonnes ( 1 Tonne = 1000kg)

some one check my maths please :)

Dave

Those numbers aren't right. I reckon:

26,000 sqr km = 26,000,000,000 sqr metres

0.25g / 1ccm = 250 kg/m3

EDIT: Imagine a cubic metre of rock. Now how much does that weigh? 25 grams? No way!
 
  • #9
billiards said:
Those numbers aren't right. I reckon:

26,000 sqr km = 26,000,000,000 sqr metres

0.25g / 1ccm = 250 kg/m3

EDIT: Imagine a cubic metre of rock. Now how much does that weigh? 25 grams? No way!
crap, I really screwed up my calcs.. doh... I'll bow to your better maths, no wonder I failed school cert maths twice haha

after using some online convertors I agree with your m2
I will work on the rest as well

Dave
 
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  • #10
using online calculators

gosh am getting such huge numbers its freaky haha
I need to work through this for my own understanding/sanity please correct me if I go wrong

so 10,000 cm2 = 1 metre2

therefore 10,000 x 10,000 x 10,000 cm = 1 m3

now here's something that has always caught me out...
thats 1 with 12 0's is that the same as 1 x 1012 or 1 x 1011 ... I was thinking 11

Dave
 
  • #11
davenn said:
using online calculators

gosh am getting such huge numbers its freaky haha
I need to work through this for my own understanding/sanity please correct me if I go wrong

so 10,000 cm2 = 1 metre2

therefore 10,000 x 10,000 x 10,000 cm = 1 m3

now here's something that has always caught me out...
thats 1 with 12 0's is that the same as 1 x 1012 or 1 x 1011 ... I was thinking 11

Dave
Hi Dave

1 m = 100 cm
1 m2 = m * m = 100 cm * 100 cm = 10,000 cm2

You got that bit right.


Next:

1 m3 = m * m * m = 100 cm * 100 cm * 100 cm = 1,000,000 cm3

You slipped up with that bit.

Incidentally: 1 with 12 0's is the same as 1012.

This stuff is not really maths. It's just working with units. Try to picture a square metre, then imagine how many square cm would fit inside it, then try to imagine a cubic metre and image how many cubic cm would fit inside it. The maths just drops out of the mental picture.

Cheers
 
  • #12
OK thanks

This stuff is not really maths. It's just working with units.

yeah something that will trip me up easily haha
i will continue working through this in this thread because I eventually want to confirm for myself the cubic volume and mass of the pumice ... besides there may be others that learn something too haha

OK so we have 26,000,000,000 metres2 and for an avg let's just pick 0.5 m thick = 13,000,000,000 m3

now the fun of converting 0.25g / cm3 to kg / m3

0.25 x 1,000,0003 (1m3) = 250,000g / 1m3 = 250kg / 1m3
which is what you said earlier, billiards :)

so 13,000,000,000 m3 x 250kg / 1m3 = 3,250,000,000,000 kg = 3,250,000,000 metric Tonnes

OK how did I go that time ? :)

Dave
 
  • #13
davenn said:
OK how did I go that time ? :)

Dave

good that time :) - I use a depth 0.6 to get the 3.9 billion verse 0.5 to get 3.2
 
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  • #14
Good but the thickness assumption is probably whacky.


One article says the pumice fragments are golf ball sized.

Now golf balls have a diameter of about 5 cm. So I would scale down your answer by a factor of 10 (dave).

Then there is the issue that this thickness is not uniform over the areal extent. You could make another assumption -- e.g. close hexagonal packing -- to account for the gaps in between the pumice fragments: multiply your answer again by 0.74.
 
  • #15
billiards said:
Good but the thickness assumption is probably whacky.


One article says the pumice fragments are golf ball sized.

Now golf balls have a diameter of about 5 cm. So I would scale down your answer by a factor of 10 (dave).

Then there is the issue that this thickness is not uniform over the areal extent. You could make another assumption -- e.g. close hexagonal packing -- to account for the gaps in between the pumice fragments: multiply your answer again by 0.74.

yes agreed, the calcs were for a uniform thickness/density, but at least I finally got my units and maths sorted out haha

D
 
  • #16
davenn said:
yes agreed, the calcs were for a uniform thickness/density, but at least I finally got my units and maths sorted out haha

D

Awesome. Glad to be able to help out
 

FAQ: Floating Rock Raft: New Zealand Questions Answered

1. What is a floating rock raft?

A floating rock raft is a natural phenomenon that occurs when a large number of stones and rocks become trapped in a mat of plant material and float on the surface of a body of water.

2. Where can floating rock rafts be found?

Floating rock rafts are most commonly found in New Zealand, particularly in the South Island's braided rivers, but they can also be found in other parts of the world such as Australia, Canada, and the United States.

3. How do floating rock rafts form?

Floating rock rafts are formed when large amounts of rocks and stones become trapped in a mat of floating plants, such as water hyacinths or willow trees, and are carried downstream by the current. Over time, the rocks and stones become entangled in the roots and stems of the plants, creating a floating mat.

4. Can floating rock rafts cause any harm?

Floating rock rafts are not typically harmful to humans, but they can cause damage to infrastructure and boats if they become too large and dense. They can also disrupt the flow of water in rivers and streams, affecting the habitats of aquatic plants and animals.

5. How long do floating rock rafts last?

The lifespan of a floating rock raft can vary depending on environmental factors such as water flow and plant growth. In general, they can last anywhere from a few days to several months before breaking apart or sinking.

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