FF16 - (HOT) Lava Nest EarthCache
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Difficulty:
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Terrain:
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Size: 
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(HOT) lava nest
A pseudocrater is a volcanic landform which resembles a true volcanic
crater, but differs in that it is not an actual vent from which lava
has erupted. Pseudocraters are also known as rootless cones, since they
are characterised by the absence of any magma conduit which connects
below the surface of the earth.
Pseudocraters are formed by steam explosions as flowing hot lava
crosses over a wet surface, such as a swamp, a lake, or a pond. The
explosive gases break through the lava surface in a manner similar to a
phreatic eruption, and the tephra builds up crater-like forms which can
appear very similar to real volcanic craters.
This earthcache takes you to a pseudocrater located in the Azores
archipelago, S. Miguel Island that looks like a giant birds nest due to
its symmetry. This location, generally known as the Ponta da Ferraria
hosts several unique volcanic features that have been classified as a
regional natural (geo)monument.
This pseudocrater was formed as a result of a strombolian eruption
(Strombolian eruptions are relatively low-level volcanic eruptions,
named after the Italian volcano named Stromboli, where such eruptions
consist of ejection of incandescent cinder, lapilli and lava bombs to
altitudes of tens to hundreds of meters. They are small to medium in
volume, with sporadic violence) that created a scoria cone and
originated a lava tongue that fell downhill to create a lava delta. The
advance of the hot lava into the sea caused a phreatic explosion which
created a conical volcanic structure disassociated from a deep mantle
source.
Pseudocraters are not very common in volcanic environments.
To claim a FIND in this earthcache please go to the supplied
coordinates and observe the structure in order to be able to answer the
following questions:
1- What is the dominant colour or dominate colours of this
pseudocrater?
2- How high do you estimate it to be?
3- Can you detect if the pseudocrater is stratified? i.e. it shows
visible layering.
4- Do you see a difference in grain size from the base to the top of
the structure?
E-mail these answers to me .
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Additional Hints
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