GC82XZR Cataclasites (Earthcache) in Southern England, United Kingdom created by angelou666

GC82XZR ▼

A cache by angelou666 Message this owner

Hidden : 1/27/2019

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Terrain:

Size: Size: other (other)

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Geocache Description:

This is an urban EarthCache in which geocachers are invited to examine an attractive wall cladding on an historic building in Southampton city centre. The learning point of this EarthCache is to get the geocacher to become familiar with cataclasites and identify which type of cataclasite the ornamental fascia is made from.

Everything you need to answer the questions is available by attending the co-ordinates and reading this lesson. I don’t anticipate you will have to research anything extra online, although you’re welcome to do so if you wish to.

Here are some keywords for this lesson:
fault: a crack in the Earth's crust
matrix: the geological material in which something is embedded
foliation: planar arrangement of structural or textural features in rock (looks like straight or wavy layers)
schistosity: a type of foliation that occurs in certain metamorphic rocks
porphyroclasts: pre-existing older crystals in a metamorphic rock that are larger than the surrounding matrix.
lithic fragments: bits of broken rock
breccia: angular rock fragments larger than 2 millimetres (0.08 inch). Breccia differs from a conglomerate, which consists of rounded rock fragments.

The posted coordinates will take you to the door of 12 Bugle Street, which currently serves as the head offices of the Red Funnel company. Officially titled the Southampton Isle of Wight and South of England Royal Mail Steam Packet Company Limited, the company runs ferries that carry passengers, vehicles and freights between the UK mainland and the Isle of Wight.

The origins of today’s company date back to 1820, when the Isle of Wight Royal Mail Steam Packet Company was established in Cowes. In 1826, the Isle of Wight Steam Packet Company was formed in Southampton, and in 1827 the two companies began co-ordinating their operations. In 1860, the two companies merged when a rival, Southampton, Isle of Wight & Portsmouth Improved Steamboat Company began operations.

And so today’s Red Funnel company, aka The Southampton, Isle of Wight and South of England Royal Mail Steam Packet Company Limited, has the longest name of a registered company in the United Kingdom. The shortened name Red Funnel was adopted after 1935 when all the company's ships had a black-topped red funnel.

The company originally operated a paddle steamer ferry service between Cowes and Southampton. In the past, it also operated trips along the south coast of England and day trips from the Isle of Wight to France, but today services are concentrated on two routes.

Clastic sedimentary rocks may have particles ranging in size from microscopic clay to huge boulders. Their names are based on their clast or grain size. The smallest grains are called clay, then silt, then sand. Grains larger that 2 millimeters are called pebbles. Shale is a rock made mostly of clay, siltstone is made up of silt-sized grains, sandstone is made of sand-sized clasts, and conglomerate is made of pebbles surrounded by a matrix of sand or mud. Around the doorframe of the company offices is some pink wall cladding. It is made of a clastic rock. Clastic rocks are made up of pieces (clasts) of pre-existing rocks. Pieces of rock are loosened or broken off in a large variety of processes. If these clasts are buried deeply, they can become compacted and cemented. Depending on the transport process of the clast, (among other things,) the clasts may be defined as conglomerates or breccia. Breccia is a clastic rock that is composed of large (over two-millimeter diameter) angular fragments. The spaces between the large fragments can be filled with a matrix of smaller particles or a mineral cement which binds the rock together. Conglomerate is a clastic rock that contains large (greater than two millimeters in diameter) rounded particles. The space between the pebbles is generally filled with smaller particles and/or a chemical cement that binds the rock together. In short, breccia clasts are generally angular, whilst conglomerates are generally rounded.

The rock you see here at GZ was formed within a fault. A fault is crack in the Earth’s crust. Typically, faults occur at the boundaries between Earth’s tectonic plates. In an active fault, the crust along the fault moves over time. This movement can cause earthquakes. In an inactive fault, the Earth’s crust no longer moves, although it used to. Where the crust has moved against itself, rock is broken and falls into these faults.

Metamorphic rock is created when an existing rock (igneous, metamorphic or sedimentary) is chemically changed by extreme heat or extreme pressure. It does not simply melt but rather the minerals within it are altered.

The British Geological Survey defines a cataclasite as a type of fault rock, which is cohesive with a poorly developed or absent schistosity, characterised by generally angular porphyroclasts and lithic fragments in a finer-grained matrix of similar composition.

Cataclasites can be subdivided according to the proportion that the fine-grained matrix forms the rock volume.

If the matrix forms less than 50% of the rock volume, the cataclasite is called a protocataclasite. (In other words, if the fine-grained host forms less than 50% of the rock volume, and the angular-shaped ‘foreign’ rocks more than 50%, it is called a protocataclasite.)
If the matrix forms between 50-90% of the rock volume, it is called a mesocataclasite.
If the matrix forms more than 90% of the rock volume, it is called an ultracataclasite.

To log this cache, please visit the published co-ordinates and answer the questions below. Once you have obtained the answers, please send them to me via email or through the Message Centre. You are free to log your find once you have contacted me. You don't have to wait for a reply. If there are any questions about your answers, I’ll contact you.

Logs without answers will be deleted. Please don’t include close up pictures in your logs that may answer the questions.

Questions:

1 Look at the matrix of the rock. Is it foliated or a random fabric?

2 Is the wall cladding cohesive or incohesive?

3 Look at the cataclasites in the matrix. Please choose one and measure its length and width.

4 With reference to the diagram, identify which type of cataclasites are present.

5 Optional, take a photo of yourself and/or your GPS in the general area of this EarthCache.

Good luck, and thanks for visiting this EarthCache!

Additional Hints (No hints available.)

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Geocache Description:

1 Look at the matrix of the rock. Is it foliated or a random fabric?

2 Is the wall cladding cohesive or incohesive?

3 Look at the cataclasites in the matrix. Please choose one and measure its length and width.

4 With reference to the diagram, identify which type of cataclasites are present.

5 Optional, take a photo of yourself and/or your GPS in the general area of this EarthCache.

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Cataclasites EarthCache

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Geocache Description:

1 Look at the matrix of the rock. Is it foliated or a random fabric?

2 Is the wall cladding cohesive or incohesive?

3 Look at the cataclasites in the matrix. Please choose one and measure its length and width.

4 With reference to the diagram, identify which type of cataclasites are present.

5 Optional, take a photo of yourself and/or your GPS in the general area of this EarthCache.

Attributes

Inventory

Bookmark Lists

Treasures