Please post a link, do not make members hunt for the source.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 ? )
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 ? )
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.
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
crap, I really screwed up my calcs.. doh... I'll bow to your better maths, no wonder I failed school cert maths twice hahabilliards 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!
Hi Davedavenn 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
This stuff is not really maths. It's just working with units.
davenn said:OK how did I go that time ? :)
Dave
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.
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
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.
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.
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.
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.
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.