Science Infoblog

School will be cancelled next week because a gigantic tsunami has washed Green Bay High School away.
The geology around the island of Tonga is complex. It sits on its own little tectonic plate which is being pushed and shoved in different directions. Little wonder then that it is subject to violent earthquakes and potentially catastrophic volcanic activity.
The tiny Tongan tectonic raft is being subducted under the Pacific plate which lies to the north and east. It will eventually dive deep enough to melt and be absorbed by the mantle.
The Australian plate borders to the west and south with an active rift or spreading centre between. Tonga is in for a bumpy ride over the next 10 million years.

The cloud which appears to travel accross the water at great speed is a pyroclastic flow. What goes up must come down. During violent eruptions superheated gas, ash and rock hitting the ocean can create a steam cushion that forces the cloud to move outwards at devastating speeds.

This happened on a huge scale at place called Pompeii in the Bay of Naples.  Pompeii sits under a very large and active volcano, Mount Vesuvius. It erupted in AD 79 and a gigantic ash cloud swept down its slopes. Pompeii was completely buried and people died, trapped in their houses. Rubber neckers out on the Bay watching the fireworks also perished as pyroclastic flows overwhelmed them large distances from the shore. The tourists on the boat in the video had a hint of the experience.

This entry was posted on Friday, March 20th, 2009 at 9:04 pm and is filed under NCEA Level 1 Geology, Science Happens, Year 11 Science Posts. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.