Saturday, December 25, 2010

Merry Christmas!

 

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(We’re taking the lazy Trendy-Tacky Table-Top Tree Tactic this year.)

Friday, December 17, 2010

Two-sided Dike

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This is one of my favorite cave features here at Oregon Caves National Monument. It’s a quartz diorite dike encrusted with calcite.
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Water (carrying minerals) flows through cracks in the marble bedrock. Quartz diorite is less permeable than marble, and when the water is unable to seep through. Instead, it flows down the surface of the dike, coating one side with calcite formations.
This is my favorite example of this, but there’s a much more prominent one along the tour route, so you should visit sometime!
If you’d like to learn more about the caves, you should read Ranger Gaelyn’s fantastic cave tour part one and part two!

Wednesday, December 8, 2010

Slick-n-slide

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Ok, so the technical name for this is “slickenside,” but I find “slickenslide” easier to remember.

(I loved the concept of slip n’ slides as a child.)

Anyway, a slickenside is created as the two sections of rock alongside a fault move past each other, slowly polishing the surfaces of the rock. This creates smooth, slick rock faces along a fault line. Sometimes you can find “slickenlines” on the slickenside, which are small, directional scrap marks left by the movement.

In the above picture, the slickenside (and fault) cross at about 35 degrees from the left to the right. In the below picture, the slickenside is more difficult to see, but is at about 60 degrees.

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That, it should be noted, is the definition of slickenside that I learned on a field trip – if anyone has a more technical definition, I would be really interested to hear it!

Thursday, December 2, 2010

Adorable, Rabies-Ridden Critters

Many years ago, I was 13, and hiking in the Grand Canyon with my family. We paused near a French family: a mother, a father, and a boy – a cute boy. He was feeding trail-mix to a chipmunk, despite the numerous, multi-lingual signs to the contrary. Luckily, my mother is fluent in French, and was willing to explain the problem to him.

Excusez-moi,” she said. “You are not allowed to feed the animals.”

The boy looked at her like she was crazy. “Pouquoi?” He asked, empty hand dangling in the air.

“Well, feeding the animals can make them sick. Also, it makes them not afraid of humans. They can become aggressive.”

Agressifs?’ he asked – just as the chipmunk lashed out and bit a chunk out of his hand.

There was shouting, and shooing, and bleeding… and my mother, explaining to his mother how to get rabies shots.

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The moral here? Don’t feed the animals, or assume cute French boys are intelligent.