Glaciers move slowly but relentlessly down valleys gouging out huge volumes of rock as they go. It takes about 400 years for snow collecting at the top of Fox glacier to reach the Fox river at the bottom.
As the glacier rips rocks away from the sides of the valley it can leave a polished surface with gouge marks. 400 years in this grinding machine can turn rocks into flour. Look at the colour of the water coming out the end of the glacier in the last video. Rocks carried by the glacier get dumped at the front and the sides when the ice melts.
Valleys formed by glacier erosion have a characteristic U shape.
North of New Zealand the Pacific tectonic plate is being subducted beneath the Australian plate. There is a lot of volcanic and earthquake activity along the collision zone.
Deep trenches form at the leading edges of subduction zones. If you watch as the pointer moves around the screen on the video and look at the elevaton numbers at the bottom ( they are negative so indicate the depth below sea level) the sea depth reaches 22,000 feet just east of tonga.
Tonga lies on a tiny microplate trapped as a rise between a spreading zone to the west and the subduction zone to the east. Recent volcanic activity appeared 10 kilometers from the southwest coast of Tongatapu, the main Tongan island. There are 36 other underwater volcanos in the vicinity.
Chemistry has its own language with words and sentences.
To a chemist the words are chemical formulae. When chemical formulae are joined together in a sentence we call this a chemical equation.
Hydrogen and oxygen mixtures explode when lit. In a test tube this explosion is heard as a “pop”. We call the test for hydrogen “the pop test”
The space shuttle is launched into space with three main engines. Each engine produces 1.8 Meganewtons of thrust. The engines are powered by liquid hydrogen and oxygen fuel stored in the large central rust coloured tank.
The space shuttle is blasted into space on the back of a mega “pop test” The two tanks on either side of the shuttle are solid fuel boosters.
Hydrogen molecules and oxygen molecules react with each other to form water molecules. A chemist rewrites this sentence as a word equation
hydrogen + oxygen —–> water
Chemists use chemical formulae instead of words. Finally chemists need to count the numbers of atoms involved. We need to have the same numbers of atoms after the reaction that we had at the start.
When we do this we end up with a fully balanced chemical equation. As far as NCEA level 1 is concerned here are the steps.
word equation…..achievement
with chemical formulae……merit
a fully balanced chemical equation…..excellence
Check out the video to see how we get a fully balanced equation for the “pop test”
try balancing the equations that describe metals reacting with acids.
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.
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