Monday, June 9, 2008

Greek earthquake

It is useful to compare the pictures from Greece, as opposed to those from China. The Chinese earthquake was a monster 'super quake', and the Greek earthquake was a thousand times smaller.

Greece is very interesting because of the tectonics. That whole area is a zone of thin crust, which is being pulled like toffee. That results in beautiful islands which are essentially normal faulted blocks, which have fallen into the earth. A Greek island typically has one very steep side, and one with a smooth slope, indicating a tilted block.

Earthquakes happen all the time in area, but the overall strain rate is much less than the Himalayas, meaning that for any given spot, it might be hundreds of years between quakes, and these quakes don't spread the damage very far, because of the thin crust. That is why everybody merrily makes their houses out of rubble! The beautiful island of Santorini is a disaster waiting to happen!

Note the perfect slope of the tilted blocks!

The thin crust also gives rise to civilization-busting volcanoes!

ps. scratch that comment of a tilted block in the picture! This is ancient volcano and caldera country. I wish I could go and check it out!

3 comments:

hypocentre said...

Unfortunately your choice of image is a poor one. What you are looking at on Santorini is the inner wall of a caldera and the flank of a volcano.

Harold Asmis said...

Ah! I've never found some good images of the tilted island blocks.

hypocentre said...

If you do get a chance to go, you should. The sunsets from the restaurants on the rim here over the caldera and the new volcanic island emerging from the centre are one of the great geological views in the world.

The remains of the Minoan town of Akrotiri, buried in the c1500 BC eruption are well worth the visit too.