✈️ FLIGHT ✈️
Flight is a sculpture by Japanese artist Keizo Ushio - The wing expresses the distant hope and the white circle represents infinity.
This Earthcache is a short walk from the Canberra Airport terminal. It aims to provide a lesson on special geological phenomenon: Xenoliths. You will learn how xenoliths are formed and how you can recognise different types.
There is a footpath that takes you all the way from the terminal, or limited free parking near the sculpure itself.
What is a xenolith and how are they formed?
An inclusion is a generic term for any foreign rock within a host rock. In the case of igneous rocks however, a specialized term “xenolith” is used to differentiate the foreign body. If the host is another rock type (i.e. metamorphic or sedimentary) then the foreign body will only be classified as an inclusion. Xenoliths are particularly fascinating to geologist because of the manner in which they are formed.
While the term xenolith literally translates to ‘foreign rock,’ some xenoliths are not entirely foreign to the host. They may be a related material (such as a gabbro xenolith in a basalt host). These foreign bodies are given a specialized term and are referred to as “autoliths” or “cognate inclusions.” These terms specifically denote that the crystalline structure of the host and the foreign rock were crystalized from the same magma.
A true xenolith, or a foreign rock in an igneous host which did not form from the same magma, is always older than their host rocks. This is because in order for the foreign body to become surrounded by the igneous rock, it must have already existed as a solid rock fragment when the magma around it solidified. This is not necessarily true with cognate inclusions.
Xenoliths are often brought to the surface by volcanic eruptions. During an eruption, magma ascends from deeper parts of the Earth and passes through the surrounding rock layers. Sometimes, pieces of these rocks break off and get carried along by the rising magma.
As the magma nears the surface and erupts, it forms volcanic rocks like basalt, granite or other types of volcanic deposits. The rock pieces that were carried along in the magma are then embedded within these volcanic rocks - xenoliths are formed. The volcanic rock containing the xenoliths is referred to as the host rock.
Xenoliths are valuable to geologists because they offer insights into the Earth's composition and processes deep beneath the surface, which are otherwise difficult to study directly. They can retain characteristics of their original formation environment, such as mineral compostions and textures that formed under high pressure and temperature conditions.
How can you recognise a xenolith?
- Xenoliths have a different mineral composition and texture compared to the surrounding host rock, making them stand out visually. Their surface might feel different than the host rock.
- Xenoliths can vary in size. They can be small pebbles or large boulders.
- They often have a different colour than the host rock.
- They are commonly found in igneous rocks, such as basalt or granite, where they have been incorporated during the magma's ascent.
- The xenolith may show signs of different metamorphic conditions, such as higher pressure or temperature minerals, compared to the host rock.
To log a find on this earthcache you must answer the following questions to be sent via message:
Using the picture above, locate the Xenolith on the sculpture under the marked "?"
1. Compare the foreign rock to the host rock, how does differ in colour and texture?
2. Using the listing above and your obersvations, is this foreign rock a true xenolith, inclusion, or autolith?
3. Do you think the foreign rock is older, younger, or the same age as the surrounding rock. Why?
4. Take a photo from the posted co-ordinates of yourself OR a personal item with "Flight" behind you and upload this to your online log
Please MESSAGE your answers to me using the the link at the top of the page underneath the name of the cache.
This method is preferred and I will reply promptly upon recieving your message. Otherwise an email is OK too!
Feel free to log your "Found It!" in the meantime, if any problems occur I will let you know
Most importantly thouugh, have fun and enjoy Flight 
This Earthcache was part of GC Project: It's Raining Caches 2025.
The project's aim was to create a rain of new geocaches to fall from the sky across the state of NSW at 9am on 19th January 2025 - 1 week before Sydney Geoquest, the first Block Party in the Southern Hemisphere.
Many legendary hiders came together to generously contribute their finest geocaches to build excitement and connection amongst the community and for all finders to enjoy years after the event.
