Archive for September, 2009

I read a good article about the geology of the antarctic peninsula and the facts discovered surrounding the mesozoic-cenezoic subduction of the pacific ocean floor.  The rocks found are similar to the Andean rocks of south america, which contain calcareous-alkaline remnants of now fragmented western margin of Gondwana extending from south america to the antarctic peninsula. The paper attempts to assess the compositional variation of amphibole in relations to host rock composition since amphibole is commonly found in all members of the magma present on the peninsula.


check out the article at google books

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Ol Doinyo Langai is a volcano in Tanzania that erupts with natrocarbonatite lava, which is rich in calcium, sodium, and potassium, and low in silica.  Because this volcano is low in silica the lava is cool.  It alternates between effusive eruptions and explosive eruptions that build large cinder and ash cones.

For the effusive erutpions, the 1983 lava filled the crater of an ash cone that formed during an eruption in 1966.  Since then the lava filled the crater. volcano

The dark areas on the previous picture show recent lava flows while the white color shows older lava flows that have reacted with rain and moisture.

For the explosive erutpions, in September 2007 an eruption threw ash thousands of meters into the air.  Ash also covered the landscape which forced residents to leave.  The eruption built a cone over 300 feet high with a steep walled crater, which can be seen in the following picture:


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In Colorado and Wyoming Diamonds have been found in 40 known diamond containing kimberlite pipes. Diamonds are very rare because the conditions suitable for their formation are also rare. The kimberlite pipes are vertical columns that were squeezed up from great depths(over 150 km deep) within the mantle, and these kimberlites have been deeply eroded (possibly 2000- 4000 feet) for hundreds of millions of years, so there must be plenty more diamonds within the nearby river and stream channels, but few have looked for them. The conditions suitable for the formation of a diamond is that it must be at extreme temperatures and pressures at great depth, and also carbon is needed because diamond is pure carbon. Diamonds have high symmetry and are isometric, and they have many crystal habits including, cubic, octahedron, dodecahedron. Diamonds have perfect cleavage in four directions that are parallel to ther octahedral faces. They are usually colorless but can rarely occur in many different colors. Diamonds are hydrophobic thus they repel water, they also are unaffected by acids. They usually concentrate in black sands in the river beds of the Wyoming and Colorade regions and can be panned for just like gold.


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Graph paper!

All right, this might not make your day, but I have to say that finding the http://www.waterproof-paper.com/graph-paper/ made me really, really happy.   I’ve searched high and low for ternary paper on occasion, but now I have a pdf!   Unfortunately, all of their grid paper is in inches not mm, but you can’t have everything…

So, here’s a challenge for my students: can you find an internet site that will help you with petrology?

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In the Sunda Islands in Indonesia on April 10, 1815 the Tambora Volcano eruption occurred and it was so loud that it could be heard from 3000 miles away in India. The blast ejected 150 cubic kilometers of tephra into the atmosphere, and ash from the eruption was found up to 1300 kilometers away from the volcano. The eruption ash shielded the sunlight causing a global cooling event that was known in 1816 as the year without a summer. This caused crops in Europe to die that in turn caused a widespread famine.The picture below is a satellite view of the Tambora caldera taken in July 2009. The caldera is 6 kilometers in diameter and nearly 1100 meters deep, minor lava flows and steam vents have occurred in recent years but nothing major has happened since 1815.


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This is an interesting article about when tools were first created by the Europeans, particulary knife/axe like tools.  It was originally determined that people in spain created axe like tools 500,000 years ago. The new study determined that the tools were actually created between 760,000 -900,000 years ago.

The method used to determine the new age was paleomagnetic dating. This method takes advantage of the earth’s magnetic field which has reversed itself often over a geologic time scale.  This article briefly discusses how scientists analyzed the polarity of magnetic minerals in rocks above and below the level where the axes were found. 



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