Tsumekizaki is tourist site located in the southern tip of Izu Peninsula, Shizuoka Prefecture, having three notable highlights.
First is a great view from cape with Tsumekizaki lighthouse.
Second is gregarious narcissus, and the blooming period is about one month from the end of December.
And third is columnar jointing exposed in Tawaraiso beach.
The beach is a valuable place, that can observe columnar jointing close at hand.
Columnar jointing is a pattern of crack complex that forms slender columns, and it is usually consist six-sided.
If you observe the columnar jointing around the posted coordinates, you will be surprised at the regular cross section patterns.
How was this mysterious complex created?
The hot lava which flowed out in the ground is cooled by atmosphere and ground, and shrinks toward center point of shrinkage distributed over equally on the cooling surfaces.
At this time, inside of the hot lava does not shrink yet, so it cause distortion between the cooling surfaces.
The lava relieves the distortion by cracking.
The cracking develops perpendicularly for isothermal line and forms slender columns.
| Task 1: |
Why is cross section of the columnar jointing usually hexahedron?
Send your answer by E-mail.
DO NOT REVEAL YOUR ANSWER IN YOUR LOG. |
| Task 2: |
Find out the columnar jointing that cross section is NOT hexahedron.
Take a photograph and upload it with your log.
Please bring your own camera.
If you post your log without the photograph, I will delete it immediately. |
| Attention: |
You should not observe the columnar jointing on a rainy day, a windy day and a billowy day.
Please wear sports shoes for your safety. |
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