Introduction:
The name of this Earth Cache comes from nearby Shirley Heights, which is worth its own visit. The Earth Cache requires you to gather answers from the rocks in front of you at GZ, based on knowledge you can gain from the "Geology of Antigua" section below.
If you are standing at GZ, you are either standing in front of or on top of a tall, unusual-looking rock. It is a good representation of the geologic history of Antigua.
The Geology of Antigua:
The island of Antigua is somewhat unique in that its three regions represent a transition between geological periods and processes. Part of the island shows the remnants of volcanic action from 7-10 million years ago. Other parts show the subsequent deposition of carbonates. So, it's a combination of igneous (volcanic) rocks overlain by limestone (sedimentary) rocks.
Unlike some other Caribbean islands, Antigua has three distinct zones that reflect its geological history.
Basal Volcanic Suite (Volcanic Region)
This volcanic region takes up the southwest 40% of the island. It is the oldest unit (Eocene-Oligocene) comprising basalt (a fine-grained volcanic rock), andesite (a dark, fine-grained brown or grayish volcanic rock), with some outcrops of dacite (similar to andensite, but with bits of quartz) in the eastern portion and thick accumulations of pyroclastic debris (The Technical Advisory Committee 2005).
Central Plain Group
This unit overlies the Basal Volcanic Suite and comprises sedimentary rocks such as mudstones (a fine-grained sedimentary rock with silt- and clay-sized grains), tuffs (porous igneous rock formed by volcanic ash and dust), arenites (sand-grained sedimentary rock), conglomerates (looks like aggregate cement, with rounded bits bound together) and some limestone (very fine-grained sedimentary rock).
Limestone Region
They are geologically the most recent and are composed of mostly fossiliferous marine limestones (limestone with a noticable quantity of fossils) and marls with coral limestones (limestone with and a few lenses of interbedded, weathered and volcanic gravel.
To Log This Earthcache:
Please submit answers to the following questions:
1. In what region are you standing? Aside from the map, what around you indicates your geological location?
2. Based on the description above, what type of rock is right in front (or under you if you are standing on top of it).
3. There are remnants of buildings all around you. Examine the materials used to build them. Based on what you see, were the buildings constructed of the same type of rock as at GZ? If not, what type, of those underlined above, seems to have been used?
4. Not required, but feel free to post a picture of the view from at or near GZ.
Bonus Question: What famous musician's "compound" is approximately 1.1km away at a compass bearing of 72deg?
Congrats to Father Monk for the FTF, and for getting the Bonus Question.