Five Islands Fault Zone - LOW TIDE EarthCache

Best to view this earthcache at low tide unless arriving by boat.

To log this earthcache, please don’t stress about answering the questions. Simply send your best attempts in a private message to me, (the cache owner), and then go ahead and log it as found. 

You don’t need to wait for my approval. All attempts will be accepted.

Go ahead and have fun learning! 

At the outcrop:

1. [REQUIRED] Please post a photo in your log of yourself or a personal item at the outcrop to prove you visited the site.
2. Compare the sandstone on the west to the lava flow rock on the east. What are the differences?
3. Look at the top of the cliff. Which type of fault is this?
4. Is the fault line between them clean, or can you see any fault breccia? Describe what you see.

This earthcache will take you to a fault line in Five Islands. Walk the beach from the parking spot to the area where you will see an abrupt change in the colour of the rocks cliffs. A fault brings the sandstone into contact with lava flows of the North Mountain Basalt.

What Is a Geologic Fault?

A fault is a crack in the Earth's crust. Typically, faults are associated with, or form, the boundaries between Earth's tectonic plates. In an active fault, the pieces of the Earth's crust along a fault move over time. The moving rocks can cause earthquakes. Inactive faults had movement along them at one time, but no longer move. The type of motion along a fault depends on the type of fault. The main types of faults are described below.

	Normal dip-slip fault Normal faults happen in areas where the rocks are pulling apart (tensile forces) so that the rocky crust of an area is able to take up more space. The rock on one side of the fault is moved down relative to the rock on the other side of the fault. Normal faults will not make an overhanging rock ledge. In a normal fault it is likely that you could walk on an exposed area of the fault.
	Reverse dip-slip fault Reverse faults happen in areas where the rocks are pushed together (compression forces) so that the rocky crust of an area must take up less space. The rock on one side of the fault is pushed up relative to rock on the other side. In a reverse fault the exposed area of the fault is often an overhang. Thus you could not walk on it. Thrust faults are a special type of reverse fault. They happen when the fault angle is very low.
	Transform (strike-slip) faults The movement along a strike slip fault is horizontal with the block of rock on one side of the fault moving in one direction and the block of rock along the other side of the fault moving in the other direction. Strike slip faults do not make cliffs or fault scarps because the blocks of rock are not moving up or down relative to each other.

Fault breccia

Fault beccia sample

Fault breccias are rocks formed by movement along a fault zone. The grinding and milling occurring when the two sides of the fault zone move along each other results in a material that is made of loose fragments. The fault zones are easily infiltrated by groundwater. Zones of fault breccia in rocks can be a hazard for the construction of tunnels and mines, as the non-cohesivness form weak places in the rock where a tunnel can collapse more easily.