Welcome to the Lock 33 Limestone Breccia Earthcache. Because this is an earthcache, there is no container to find here. Instead, you are looking for a geological feature called breccia. In order to log this cache as found, please complete the following two tasks (logging requirements):
1. Send you answers to the following three (3) questions to the CO via Geovcaching Messages, email, or by any other means available to you.
a) Pick a sample of breccia from the stones located at GZ. There are at least two different types of breccia noticable at GZ, with one type being more prevalent than the other. Which type do you feel is more prevalent, based on your observations and the reading below?
b) Based on the reading below, how do you think these breccia were formed?
c) How many different breccia samples do you see in the rocks at GZ? If less than 20, please count them. If your answer is more than 30 please make an estimate.
2. Take a photo of yourself with lock 33 in the background to prove you visited the location.
Now that you know what you need to do to log this earthcache, let's answer some basic questions:
What is Breccia?
Breccia is a term that describes sedimentary rock made of clasts that are composed of large angular fragments (over 2mm in diameter). The spaces between the large angular fragments are filled with a matrix of smaller particles and a mineral cement that binds the rock together.
When you hear the word "breccia" used in reference to a rock or rock material, it is fairly safe to assume that it means angular-shaped pieces.
A true Breccia is considered to be a “Sedimentary rock”. Sedimentary rocks are formed by the collection and eventual compression of mineral or organic particles at the earth’s surface, followed by cementation. Sedimentary rocks are deposited in layers as strata, forming a structure called bedding.
What is Breccia's Composition?
Breccia has many compositions. Its composition is mainly determined by the rock and mineral material that the angular fragments were produced from. The climate of the source area can also influence composition. Most breccia are a mix of rock fragments and mineral grains.
The type of rock that the fragments were produced from is often used as an adjective when referring to the rock. Some examples: sandstone breccia, limestone breccia, granite breccia, chert breccia, basalt breccia, and others.
The rocks located at GZ are made of limestone and thus these samples would be considered limestone breccia.
Different Classifications of Sedimentary Breccia
Collapse Breccia:
Broken rock that originates from a cavern or magma chamber collapse, and then rejoined through heat and/or pressure.
Fault Breccia or Tectonic Breccia:
Broken rock found in the contact area between two fault blocks and produced by movement of the fault.
Flow Breccia:
A lava texture produced when the crust of a lava flow is broken and jumbled during movement. Another example of Metamorphic Breccia.
Fold Breccia:
A breccia formed by the folding and breakage of thin, brittle rock layers which are inter-layered with incompetent, ductile layers. Through an increase of pressure, these rocks have been cemented together, and with infilling of sedimentary material.
Impact Breccia:
A deposit of angular rock debris produced by the impact of an asteroid or other cosmic body, when it slams into the earth. These catastrophic impacts literally transform surface material into new rock types. As they have been altered by heat and pressure, Impact Breccia is considered a metamorphic rock.
What are the Uses of Breccia?
The rock, breccia, has very few uses. It can be used as fill or road base where the technical requirements are minimal. It is rarely used in important projects because its composition, degree of cementation and competence are highly variable.
At GZ, you will find a collection of limestone blocks that are used for landscaping purposes.
Source: https://geology.com/rocks/breccia.shtml