Bridging the Gap - An Accidental Meeting EarthCache

There are a number of national parks that stretch over a distance of some 600 kilometres along Western Australia’s south coast, from just east of Augusta to east of Esperence. They fall mainly within the one geological province known as the Albany-Fraser Orogen.

An orogen is a mountain range, or more typically the remains of a mountain range. It is the belt of rocks that was at the interface of colliding continents where the intense heat and pressure they experienced due to deep burial and compression resulted in dramatic changes to their mineralogy and structure.

The Albany-Fraser Orogen was formed by the collision of the Australian continental plate and a continent to the south called Mawson, remnants of which exist in Antarctica.

The granite around Albany is the uplifted and eroded core of this ancient mountain range. There are some fine examples of coastal erosion of this granite in the area. Two of these are the Natural Bridge and the Gap. At the Natural Bridge erosion has progressed to leave a large block of granite suspended, while at the Gap the force of the ocean has eroded and eventually removed numerous joint-bounded granite blocks. Although this has happened right along the coast, here it has left a spectacular result (at least for the time being!).

To log this cache you need to

A. Visit the information sign at the given co-ordinates and answer the following questions:-

1.  Near what site in Antarctica can the identical rocks be found?

2.  According to the sign, what will the natural bridge eventually become?

3.  Australia and Antarctica are drifting further apart. By how far each year?

4.  The bands and folds of dark rock that can be seen in places, are what kind of rock?

B. Post a photograph of your visit to the area (but please don’t include the sign).

Please email your answers for question A so we can give you the OK to claim a find, then you can log it and upload your photo.