Sand Volcanoes at Ross. EarthCache

This Earthcache will hopefully explain to you how 'Sand Volcanoes' were formed here in West Clare which was previously to be found on the edge of a large continent, they are fossilised and thus preserved along with the event which most likely caused their formation all those years ago

A sand volcano also known as a 'sand blow' or a 'sand boil' is a shallow pile of sand formed by the ejection of wet sand onto a surface through a weak point. This forms a cone which looks like a miniature volcano complete with crater on top. These can vary in size from a couple of meters to a few cm.

Once upon a time this area was part of a huge delta and river system. Over a period of 7.5 million years (318.5 to 311 million years ago) this massive river system carried sand, silt and mud to the sea. Over time it deposited vast amounts of sediment and material which created a large submarine fan delta just off the coast of an ancient continent. Over time these mud and sand layers formed the different bands of rock that can be seen here today.

Here at Ross the manner in which the rock is displayed indicates that from time to time throughout this period and as a possible result of under water avalanches due to the changing weight of material, the submarine fan become unstable in places, one such collapse or slump can clearly be seen at the far side of the Cove as you look towards these coordinates from the car park. Here the sediment gave way. Immediately above this slump some 'Sand Volcanoes' were formed as water and liquefied sand oozed up out of and above the slump as it settled.

The following set of images I got permission to use Courtesy of the Nova Scotia Museum and they illustrate this phenomenon pretty well though not exactly as they occurred here.

This next set of images show some more recently formed sand volcanoes. They are from the Christchurch area in New Zealand and were formed during the 7.1 magnitude earthquake there in September 2010, Their formation would have come about slightly differently but the same principles apply to the those in this Earthcache. Pressure and vibration or movement caused the wet sandy layers to liquefy and force their way through the layer above.

• You will need a measuring tape or something similar.
• You should save the image below to your device or print a copy so you can use on site it to find the answers to Q1.

Please send the answers using the message center and not by email because I may miss them there.

1. There are several of these 'volcanoes' here but I want you to examine the one in the picture and make some observations, size etc The 'crater' on top is not circular but roughly elliptical. Can you measure the internal length and width and the external length and width and give me the the values for a,b,c & d in the image above?
   
2. Is the external surface rough or smooth?
3. As mentioned the 'volcano' is part of a cluster and there are several touching each other here. In the center of a neighbouring volcano the central crater or plug is missing leaving a cylindrical hole. What is its diameter at the top and what is its depth?
4. As you make your way to GZ or if you visited the neighbouring EC first you will be well aware of the fact that the Layers of Sandstone and Mudstone here are constantly RISING and DIPPING. Now examine the layer the volcanoes are on at GZ is it (i) flat or horizontal. (ii) inclined towards the ocean. (iii) Inclined away from it?

An explanation as to why these volcanoes are so shallow is something called the angle of repose, now in this case it may well be distorted but it does give an idea.
Definition: The angle of repose of a granular material is the steepest angle of descent or dip relative to the horizontal plane to which a material can be piled without slumping.

I have earned GSA's highest level:

Needless to say you may log the find but I will delete any logs that I have received no answers for or are inaccurate. photos that don't give clues to the answers are most welcome but not obligatory