Stretching puts Earth into shape over winter

Electronic Telegraph ^ | December 14, 2001 | By Roger Highfield, Science Editor

[Map Kernow]

SNOW, ice and frost are deforming the shape of the Earth.

Scientists have discovered that it is slowly stretching so that the North Pole is heading towards the centre of the world and the Equator is migrating northward.

The Earth is experiencing seasonal "stretching" in response to increased winter loading of the ground and corresponding atmospheric and gravitational changes.

As a result, compression and expansion in opposite hemispheres occurs. It does not change the Earth's overall shape, but stretches its surface and so affects site co-ordinates," said Prof Geoffrey Blewitt of the University of Nevada, Reno, who reports the find with colleagues in the journal Science.

By studying data from the global positioning system of satellites, they found that the Earth deforms without changing.

Prof Blewitt said the discovery "amazed us, but we delved into the theory of the Earth's response to the weight of surface loading, the maths tell us how this is possible."

Imagine taking a balloon in the perfect shape of a sphere, then squeezing one half of it so it compresses that half and the opposite half expands.

"There is a way to do this so that the balloon ends up being spherical (the same shape), but one half of the surface is compressed, and the other side stretched," he said.

These factors combine to compress the northern hemisphere and expand the southern hemisphere.

[Map Kernow]

Environmental degradation the Sierra Club can't blame on humankind.

[RnMomof7]

ping

[Sloopy]

So, does this mean global warming (if it exists) is a good thing? Sort of a counter balance to the freezing and stretching?

[gcruse]

"There is a way to do this so that the balloon ends up
being spherical (the same shape), but one half of the surface is
compressed, and the other side stretched," he said.

If the shape doesn't change, what does?  And if the
shape doesn't change, why would a GPS register
anything differently?

[Don W]

The SHAPE (an ovoid sphere) remains the same, but its proportions are altered. The cooler half shrinks a bit, and the warmer half expands.

As for the co-ordiantes changing, think soccer ball vs basketball: xyz on the soccerball is inside the basketball if they both occupy the same space. Think of the earth as BOTH, but the basketball is the hot bit, and the soccerball is the cool bit. The SHAPE is the same, but they are different sizes. And the size of each half changes with the seasons.

[gcruse]

My head hurts. ;)

[Don W]

Just be glad I didn't get into a discussion of differential physics < VBG >.

[RightWhale]

Seasonal heating and cooling penetrates the surface only a few feet. Any seasonal or climatic dimensional changes would be due to the weight of ice, snow on the surface. It is well known, and was even before GPS, that Scandinavia is still rising since the most recent Ice Age, it is called glacial rebound.

Tides are another effect. Ocean tides are well-known and have been since the first human went clam-digging on the shore. The land is also subject to tidal motion.

There is another effect that gradually moves survey monuments. Land flows downhill, slowly. Any survey monument that is not embedded in bedrock will move with the land.

And of course there are tectonic forces, even Wegener's continental drift hypothesis has finally been accepted, not, of course, while he was still living.

Here in Fairbanks where it goes from 80 degrees in summer to -60 in winter, the effect is only skin deep. Most materials contract when cooled, but this wouldn't amount to much compared to the radius of the earth, and wouldn't change the weight of the land, only its volume, and only through the couple of feet in depth affected. 20 feet, tops.