GC3JJ2H Tatami Ishi (Earthcache) in Okinawa, Japan created by TeamBrudvik

GC3JJ2H ▼

A cache by TeamBrudvik Message this owner

Hidden : 5/3/2012

Difficulty:

Terrain:

Size: Size: not chosen (not chosen)

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Geocache Description:

Tatami Ishi is a series of more than 1000 pentagonal and hexagonal rocks that look like turtle shells that is connected to each other. The pattern were created for more than 20 million years ago when a concentration of lava cooled and splintered into rocks. Wave erosion has worn the rocks nearly flat over the years. Such formations are extremely rare in the world and the area has been designated a national monument in Okinawa.

How are the formation created?

A similar formation can be seen when mud dries. When the mud looses water it cracks in symmetrical polygon shapes. The reason for this is because when the mud looses water it starts to shrink and the contraction is relieved by breaking. When it happen it naturally seek the most stable position in the form of polygons with vertical cracks. Basalt and lava behave similarly as mud. It does not dry, but it shrink when it becomes cold and brittle, and relieves stress by cracking. The cracking produces a polygon pattern that extends trough the lava flow. The most common shape are six sided, but also four, five, seven and eight sided are relative common. The perfection of the polygon pattern depends on the composition of the lava and on it's cooling speed.

Cache requirements

Send me the answer to the following questions:
1) What factor of the cooling process determine the size of the rocks?
2) What is the average size of the rocks that can you see?
3) What three numbers do you see at the bottom left of the information board?

Optional: Take a picture of you or your GPS in front of the rock formation and post it in your log