Baddaginnie Boys Earthcache

To comply with the new Earthcache hiding guidelines, "List logging tasks at the top of the cache description." (1.4.24) The questions are now at both the top of the page as well as below the lesson....reading the lesson will help you answer the questions...

Earth lesson Questions: 

With your back to the road you need to inspect the right hand side of the monument where you will find an obvious inclusion...

Now to the test! To log this earthcache, please answer the following 2 questions and forward your answers to us and log with your photo:

1) Using your new knowledge, do you think this inclusion is a xenolith? What leads you to this answer?

2) Can you see any other inclusions on other parts of the monument? Describe where they are and indicate if they seem to be xenoliths?

3) Please attach a photo to your log of yourself, or a personal object, with the monument in the background, distant enough to not show any spoiler information.

You may log the cache as soon as you submit your answers to us via messenger.

Logs without accompanying answers sent or without a photo uploaded may be deleted without notice. No need to strain your brain, the questions are not that hard, just have a go! 

THE LESSON.....

In geology, there are lots of terms that are “foreign”….. “enveloped” in a lot of language that often makes you feel you need to have PhD in Geology to understand it all! It doesn’t have to be this way! Break things down, like a “chip off the old block” and the terminology can become clearer. 

If you are like we were when we first attempted to complete earthcaches it seemed like such a "steep mountain" & was overwhelming (I am pretty sure we made a total dog's breakfast of our first few answering attempts!)….it just seemed like there was so much to know and learn! Desmond Tutu once wisely said “there is only one way to eat an elephant: one bite at a time.” In other words, the seemingly impossible can be accomplished gradually, taking on just a little bit at a time. In the same vein, the more earthcaches you attempt, one at a time, the more you learn and build on your accumulated knowledge….and before long you will find yourself reading an earthcache page and thinking…oh, I know this! If you are like me, you’ll soon find yourself seeking out the earthcache symbol wherever you go!

And so, without further ado....The Lesson...

For the this earthcache we are looking at learning just 2 terms; Inclusions and Xenoliths.

An inclusion is any material that is trapped inside another during its formation. Within geological parameters, the term “inclusion” can encompass a few different occurrences. In mineralogy; an inclusion is any material that is trapped inside a mineral during its formation. In gemology; an inclusion is a characteristic enclosed within a gemstone, or reaching its surface from the interior. Inclusions are usually other minerals or rocks, but the term may also be used in relation to trapped water, gas or petroleum. Liquid or vapour inclusions are known as “fluid inclusions”, like a microscopic bubble of liquid and/or gas that is trapped within a crystal, for example. In the case of amber it is possible to find organic matter such as insects or plants as inclusions within the fossilised resin.

Baltic amber inclusions - 40-50 million year old ants.

A xenolith (xeno : foreign; lith : stone) is older "country" or basement rock that becomes enveloped in a larger, younger rock during the latter's development and solidification. In geology, the term xenolith is almost exclusively used to describe inclusions in igneous rock during magma emplacement and eruption. Magma rises to the Earths surface through deep cracks, faults or pipes between the Earth's crust and mantle, and as the molten material rises, it tears off bits and pieces of the magma pipe in which it is travelling. Xenoliths may be engulfed as magma passes along the margins of a magma chamber, ie the older country rock may be torn loose or blasted from the walls of an erupting lava conduit or explosive diatreme or picked up along the base of a lava flow on the Earth's surface. These bits and pieces become trapped in the magma but do not melt into it, becoming xenoliths. A xenolith may lose its unique qualities if it melts into the surrounding magma. If the surrounding magma causes the xenolith to become molten it then ceases being a xenolith, it mixes with the surrounding molten material and changing the mineral make up of the younger rock….thus as it cools and solidifies it becomes a metamorphic rock.

Schematic illustration of a diatreme pipe eruption.

Although the term xenolith is most commonly associated with igneous inclusions, a broader definition could include rock fragments which have become encased in sedimentary rock. 

To be considered a true xenolith, the included rock must be identifiably different (a different colour, texture, density and mineral content) from the surrounding rock in which it is enveloped (an included rock of similar rock type is called an autolith, but that’s a whole different story!). Xenoliths can be as small as a grain of sand or as large as a football, and as long as several metres.

Xenoliths provide important information about the composition of the otherwise inaccessible mantle. 

An example of a Xenolith, a chunk of the rock peridotite is embedded in basalt rock.

So by definition; any Xenolith is an inclusion BUT not all inclusions are xenoliths. Hopefully all that is crystal clear…or at least clearer than mud!

Glossary…(a brief wrap of what you have learned)

Autolith: pieces of older rock within a younger rock that is related to the younger rock, having similar or the same colour, texture, density and mineral content.

Country or basement rock: rock that’s native or local to an area, the term is used to denote the usual strata of a region.

Diatreme: (dia : through, across, over; trema : hole, aperture) when related to volcanics it is a funnel-shaped pipe cutting through basement rock generally formed by gaseous explosions.

Igneous rock: having solidified from lava or magma.

Inclusion: any material trapped inside another during its formation.

Metamorphic rock: a rock that has undergone transformation by heat, pressure, or other natural agencies

Sedimentary rock: formed by or from deposits of sediment.

Xenolith: a fragment of country rock included within another, younger rock having a noticeably different colour, texture, density and mineral content than the rock it is embedded in.

And so, to the earthcache…..

Here you are facing the Baddaginnie War memorial. The monument was originally erected to commemorate those from the district who died in service of Australia during WW1. It now commemorates those who served in all wars and conflicts.
 

With your back to the road you need to inspect the right hand side of the monument where you will find an obvious inclusion...

Now to the test! To log this earthcache, please answer the following questions:

1. Using your new knowledge, do you think this inclusion is a xenolith? What leads you to this answer?
2. Can you see any other inclusions on other parts of the monument? Describe where they are and indicate if they seem to be xenoliths?
3. Please attach a photo to your log of yourself, or a personal object, with the monument in the background, distant enough to not show any spoiler information.

You are welcome to log a find as soon as you message the answers to us. There is no need to wait for confirmation. If a question needs clarification we'll be in touch. However, as this is an Earhcache, you must submit your answers to me within 14 days, or your Find log may be deleted without notice.