Saturday, April 05, 2008

Comment of the day

The Times reports:

So much ice in Iceland has melted in the past century that the pressure on the land beneath has lessened, which allows more of the rock deep in the ground to turn to magma. Until the ice melted, the pressure was so intense that the rock remained solid.
[...]
Since 1890 the ice-cap has lost 10 per cent of its mass, which has allowed the land to rise by up to 25m (82ft) a year.
Michael Ryan left this comment:
Pretty impressive! The area that was under the ice cap has been rising by 25 meters per year, presumably for the last 118 years. So now there is a mountain there nearly 10,000 ft tall where before there was a flat plain? Remarkable!


UPDATE: Appropriately, the comment left by Dearieme is worth bumping to the front page: "Ice is a famous exception, but solids are almost always denser than the corresponding liquid. So if the rock melts, Iceland should slump, not rise. The author may not understand what he's talking about - Scotland is still rising after the removal of its ice more than 12000 years ago, because, on that timescale, rock flows upwards in response to the removal of the overburden. The prophetess Deborah had views on the topic."

5 comments:

dearieme said...

Ice is a famous exception, but solids are almost always denser than the corresponding liquid. So if the rock melts, Iceland should slump, not rise. The author may not understand what he's talking about - Scotland is still rising after the removal of its ice more than 12000 years ago, because, on that timescale, rock flows upwards in response to the removal of the overburden. The prophetess Deborah had views on the topic.

dearieme said...

Oops, there's a flaw in my logic there. Apologies.

Peter Risdon said...

You mean if liquid is less dense it should occupy greater volume?

Even so, liquids are indirectly compressible, often, aren't they? Dissolved gas.

Peter Risdon said...

Oh, and in a short timescale displacement?

dearieme said...

You mean if liquid is less dense it should occupy greater volume?

YES

Oh, and in a short timescale displacement?

YUP