When you arrive at GZ you will find yourself at an information point with parking, shelter and picnic tables at the base of Pine Mountain. There is lots of information about the geology, flora and fauna of the local area as well as about the bushfires in the area a few years ago. There are also a few artworks and some binoculars to give you a better view of the mountain.
There is ample parking for cars or even caravans and trucks.
Pine Mountain
Pine Mountain on the border of Victoria and New South Wales is a single gigantic rock argued to be the largest in Australia, being 1.5 times the size of Uluru. It is composed of a unique type of pink and grey granite known as ‘Leucogranite.’
The gigantic red granite monolith was uplifted to its present height of 1062 m more than 2 million years ago. Since then erosion has highlighted the steep eastern side, established several creeks, and in the upper area, created small rock pools which contain shrimp and tadpoles despite annual drying, and large granite marbles 2-3.5 m in diameter.
Today, Pine Mountain is largely covered by vegetation, humbly disguising its significance as one of Australia’s largest rock’s.
Volcanic activity is an important mechanism responsible for the creation of many mountains. Mountains are formed when molten rock pushes its way up to the Earth’s crust. Dome mountains are created when the magma lifts the rock layers, but does not penetrate the surface, while volcanic mountains are formed when the magma erupts and piles upon the surface.
Igneous rock
Igneous rock or magmatic rock, is one of the three main rock types, the others being sedimentary and metamorphic. Igneous rocks are formed through the cooling and solidification of magma or lava.
Igneous rocks can be either intrusive (plutonic) or extrusive (volcanic).
Intrusive
Intrusive igneous rocks make up the majority of igneous rocks and are formed from magma that cools and solidifies within the crust of a planet. Bodies of intrusive rock are known intrusions and are surrounded by pre-existing rock (called country rock). The country rock is an excellent thermal insulator, so the magma cools slowly, and intrusive rocks are coarse-grained. The mineral grains in such rocks can generally be identified with the naked eye. Intrusions can be classified according to the shape and size of the intrusive body and its relation to the bedding of the country rock into which it intrudes. Typical intrusive bodies are batholiths, stocks, laccoliths, sills and dikes. Common intrusive rocks are granite gabbro, or diorite.
Basic types of intrusions:
- Laccolith
- Small dike
- Batholith
- Dike
- Sill
- Volcanic neck, pipe
- Lopolith
Extrusive
Extrusive igneous rock, also known as volcanic rock, is formed by the cooling of molten magma on the earth's surface. The magma, which is brought to the surface through fissures or volcanic eruptions, rapidly solidifies. Hence such rocks are fine-grained or even glassy. Basalt is the most common extrusive igneous rock and forms lava flows, lava sheets and lava plateaus.
Logging tasks
Please message me through Geocaching.com with your answers within a week of logging, you can post your log straight away.
- Given that Pine Mountain is composed of Leucogranite, was it formed by an intrusive or an extrusive process?
- There are some rocks edging the carpark area where you are. Do you think they are intrusive or extrusive rocks and why?
- Please post a photo in your log of yourself, or something with your geocaching name, with Pine Mountain in the background.
Source: https://en.wikipedia.org/wiki/Igneous_rock
https://en.wikipedia.org/wiki/Pine_Mountain_(Victoria)