This is another cache aimed at the younger crowd that will hopefully help them better understand some of the rock formations we see around us. (Parents please keep an eye on your children here as it is on the road side - keep an eye out for cars)
No not that kind of intruder :-) The aim of this cache is to teach you all about volcanic inturders or intrusions as they are more comonly known.
There are a few types of intrusions and they have some rather unusual names - here are some of them:
Batholith: a large igneous intrusive rock that forms from cooled magma deep in the Earth's crust. (3)
Dike: a relatively narrow tube-like igneous intrusive rock, often nearly vertical (2 and 4)
Laccolith: Invasive ignious rock with roughly flat base and convex top, usually with a feeder pipe or dike below (1)
Lopolith: Invasive ignious rock with roughly flat top and a shallow convex base, may have a feeder dike or pipe below (7)
Volcanic pipe or volcanic neck: a tubular roughly vertical Intusion that may have been a feeder vent for a volcano (6)
Sill: a relatively thin tube-like igneous intrusive rock that has intruded along bedding planes(5)
There are a few others but we dont want to get to complicated here so we will leave it at that. Here is an example in picture form for you to make it easier to understand where the nubers are the same as the ones in the explination above
Ok now that you know a bit more about Volcanic Intrusions lets see if you can answer a few questions that you will find the answers to at the published coordinates.
1) Across the valley from the published coordinates you will notice an intrusion that has been exposed by erosion, can you identify what type it is? ... why do you think this?
2) If you look at the colour of the intruding rock and the colour of the bank behind you when facing the intrusion at the published coordinates you will notice there is a stark contrast between them, can you give a possible reason/s for this.
3) Optional – take a photo of your GPS and or yourself with the intrusion in the background
References
1) Encyclopædia Britannica
2) Wikipedia