Horse Head Formations EarthCache

Horse Head Formations

Beach Meadows is a settlement in the Region of Queens Municipality, Nova Scotia. It is the site of Beach Meadows Beach Park. The communities in this area were settled principally by German folk, who long preserved their language and customs.

Across from the parking area is Coffin’s Island, named after Peleg Coffin, one of the first settlers. Earlier, it was known as Bear Island. It is said that beach rock was gathered on the island for ballast, which eventually reached places as far away as Labrador and the West Indies. The first lighthouse was built in 1812 and it was destroyed by fire in 1913.

Earthcache

At the parking area you can read about the island and see the horse head rock. Start here to make your way to the earthcache. It is easier when the tide is not high but can still be done at high tide. At ground zero there are four formations that you are looking for, a fold, pressure breaks, veins and quartz slabs.

Folds

The folds arise as a result of the tectonic pressure and stress in the rocks and rather than fracture, they fold. They are easily visualized by the loss of horizontality of the strata. Tectonic forces acting on sedimentary rocks can create a number of characteristics and changes to the rock formation. Sedimentary rocks are more flexible than the metamorphic, and when the thrust is intense enough it makes them fold as if they were a piece of paper. The rock layers in folds can be folded in two ways: as a result of Transverse bending and by Longitudinal bending. Transverse bending is across the rock grain, while Longitudinal is along the rock grain or axis of the fold.

Fractures

Fractures in rocks can be formed either due to compression or tension. Fractures due to compression include thrust faults. Fractures may also be a result from shear or tensile stress. Some of the primary mechanisms are discussed below.

There are three modes of fractures that occur (regardless of mechanism):

• Mode I crack – Opening mode (a tensile stress normal to the plane of the crack)

• Mode II crack – Sliding mode (a shear stress acting parallel to the plane of the crack and perpendicular to the crack front)

• Mode III crack – Tearing mode (a shear stress acting parallel to the plane of the crack and parallel to the crack front)

Veins

Veins generally need either hydraulic pressure in excess of hydrostatic pressure (to form hydraulic fractures or hydrofracture breccias) or they need open spaces or fractures, which requires a plane of extension within the rock mass. There are two distinct types: fissure veins and ladder veins.

Fissure veins are formed in two stages, sometimes greatly separated in time; first the fissure is formed, and then it is filled with ore. There are several varieties: simple, with relatively straight, parallel walls; chambered, with irregular, fragmented walls; dilation, or lenticular, with fat lenses in a string or roughly parallel in schists; sheeted, with several distinct, closely spaced, parallel fractures; and composite, with several roughly parallel fissures and connecting diagonals in partially replaced rock.

Ladder veins are short, rather regularly spaced, roughly parallel fractures that traverse dikes (tabular bodies of igneous rocks) from wall to wall. Their width is restricted to the width of the dike, but they may extend great distances along it. Ladder veins are not as numerous or important as fissure veins.

Quartz slabs

The simplest type of a quartz vein is the filling of an already present crack in rocks. The crack might form during folding of the rock in mountain-building processes, by shattering during tectonic events, by a decrease in pressure during the uplift of a rock, or because a rock cools down and shrinks. Hot brines that percolate the rocks and originate at greater depths with higher temperatures will precipitate the minerals they carry with them in cracks at lower temperatures and pressures. This process may continue until the crack is completely filled or may stop before, leaving "pockets" in the vein that are sometimes outlined by crystals.

The result is milky quartz, either massive or made of interlocked milky quartz crystals. Later, when the crystal growth slows down, the crystals may get less milky or even clear. In the majority of quartz veins, most of the quartz is precipitated as massive, milky quartz. Well-formed crystals, if found at all, are only a small portion of the vein filling.

Below is an image of a quartz slab on top of a piece of granite.

To log this Earthcache visit the viewing location.  Please answer the following questions and send in a timely manner to my geocaching profile or email. Answers not received will result in deleted logs.

Remember this is a D5, so you answers must respect the difficulty.

Look in the general area of ground zero to find all the formations

Questions

Fold

1 - How long and in what direction is/are the fold(s) going?

2 - What type of bend is present on the fold, longitudinal or transverse? 

Fractures

3 - What type of fractures are present, Open, Tearing, or Sliding?

4 - Do they all run in the same direction, Why?

Veins

5 - Why type of veins are presents, fissure or ladder?

6 - What caused the veins to form?

Quartz Slabs

7 - What is the size and shape of the Quartz slabs? (see image for example)

8 - Why are these Quartz slabs not veins or were they; explain?

Final

9 - What came first, the fractures or the veins and why?

10 - Post a picture in your log with a personal item or hand in picture to prove you were there.

[REQUIRED] In accordance with the updated guidelines from Geocaching Headquarters published in June 2019, photos are now an acceptable logging requirement and WILL BE REQUIRED TO LOG THIS CACHE. Please provide a photo of yourself or a personal item in the picture to prove you visited the site.