Moel Hebog Pillow Lava EarthCache
Hidden : 2/12/2013
Difficulty:
2 out of 5
Terrain:
4 out of 5

Size: Size: not chosen (not chosen)

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Geocache Description:


This is an Earthcache there is no container to find, please do not remove any rocks or lava.




Pillow Lava


What are Pillow Lavas:

Pillow lavas are “elongated lava “pillows” that are formed by repeated oozing and quenching of the hot basalt” This procedure is in a 2 step sequence:

1) A stretchy glassy crust forms on the recent extruded lava, forming an extended pillow,

2) Pressure builds until the crust breaks and new basalt extrudes like toothpaste, forming another pillow. This goes on until the lava is thick and ready to be deposited. The pillows are described as “bulbous, spherical, or tubular lobes of lava” (Nemo). During the formation, the recent pillows erupt from the and flow outward until they freeze. This process produces steep-sided mounds or ridges that can grow very thick.


geology diagram


What are the characteristics of a Pillow Lava?:

1) There are chilled glass selvedges around the pillows. This is formed by the rapid cooling of the lava by the water.

2) Pillow tops are typically rounded upward, while their under surfaces may be smooth, curved up or propelled down between underlying pillows.

3) Gas cavities are usually located on the upper part of the pillow lavas.

4) In some instances, clay and sand may be evident between the spaces of the pillows.

5) Pillows are solid and not typically hollow. They frequently have scuff marks on their sides that appear during the extrusion.

Ground Zero


The Cache Location


Where can pillow lavas be found?:

They can be found in oceans, lakes, rivers and glaciers. They have been found in Scotland, United States( Hawaii, Washington State, Oregon), Iceland, Canada, the island of Crete, and possibly many more.

Early Life Found in Pillow Lavas:

Mineralized tubes the size of micrometers were found in pillow lava rims that were in the Mesoarchean Barberton Greenstone Belt that is located in South Africa. These tubes prove that there was submarine microbial action during Earth’s early history. The borders of the tubes hold organic carbon. The overlying of metamorphic and magmatic dating of the pillow lavas imply that microbial life populated these subdivisions of volcanic rocks right after their explosion.



The Cache


We set this cache on an extremely wet day walking approx 9 miles with the rain falling for every step of the way, so excuse the slightly fuzzy picture at ground zero. Hope you enjoy the cache and do so in much nicer weather than we had in setting it !! As with all high mountain/hill walks please wear appropriate footware stout boots preferably, and wet weather gear also.

Logging Requirements :


Please e-mail me the answers to the following Questions, also a picture at GZ would be nice :

1. Observe the pillow lava how many shapes can you see and what are they ?

2. Approx what is the average size of pillows in the immediate area please estimate the height and width of one of them

3. Gas cavities are normally found on what part of the lava and please explain why you think this is.

4. How many years ago do you think the Pillow Lava was formed.



Permission for this cache was kindly granted by CCW


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Additional Hints (Decrypt)

Whfg ybbx sbe fbzr hahfhny ebpxf !

Decryption Key

A|B|C|D|E|F|G|H|I|J|K|L|M
-------------------------
N|O|P|Q|R|S|T|U|V|W|X|Y|Z

(letter above equals below, and vice versa)


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