Camel's Hump is a mountain that is part of the Macedon Ranges of the Great Dividing Range, located in the Central Highlands region of Victoria, Australia. This Earth Cache will see you at the mountain top which has an elevation of 1,011 metres, the highest in the region. It is located approximately 65 kilometres northwest of Melbourne.
Camel's Hump is a mamelon (from French mamelon, "nipple") which is a rock formation created by eruption of relatively thick or stiff lava through a narrow vent in the bedrock. Because the lava is not fluid, it does not flow away; instead it congeals around the vent, forming a small hill or mound on the surface.
Camel's Hump is a steep, craggy dome of lava that forms a prominent and peculiar profile above the surface of Mount Macedon. It is not related to the Macedon igneous rocks (Devonian lavas) but is one of a distinctive group of volcanoes that produced a relatively silica-rich lave (soda trachyte) of high viscosity. These lavas are confined to a small area around Woodend and Trentham and include Hanging Rock. Averaging 6 million to 7 million years in age, they are the oldest rocks of the Newer Volcanics. At Camels Hump the lava formed a dome or plug at the vent and did not deform into an elongated lava flow. The rock is well exposed as cliffs. Radiometric dating of lava places the age of eruption as 6.14 million years ago. Small crystals of an unusual mineral (ferroan rectorate) occur in high temperature vesicles in the lava.
Trachyte is an igneous volcanic rock which can be so fine grained that their component mineral crystals are not detectable by the unaided eye through to large crystal grains. It is the volcanic equivalent of syenite (a coarse-grained grey igneous rock composed mainly of alkali feldspar and ferromagnesian). The mineral assemblage consists of essential alkali feldspar; relatively minor plagioclase and quartz or a feldspathoid such as nepheline may also be present. Biotite, clinopyroxene and olivine are common accessory minerals.
Trachyte
Camels Hump is an unusual volcano for Victoria both in terms of its form and rock composition. It lies along the time boundary between the Older Volcanics and Newer Volcanics series (Late Miocene). This site is an important teaching and reference site to illustrate the influence of lava type on volcano form and is one of the best examples of its type in Victoria. Recent isotopic dating of the rock material has supported earlier (1930’s) evaluation of the age and origin of the volcanic material.
These questions can be answered from two view points at the top of Camel's Hump and an inforamtion sign close to the car park.
Please be careful of the very steep drop, you don't need to venture down the cliff face.
Questions
Q1 Describe the rock in detail that is located away from the viewing platform (colours and texture).
Q2 Describe the rock in front of you as you look out to the valley below. (This is a popular rock climbing spot) to the left and right. The coordinates will have you left of a tree and a great spot to take a selfie.
Q3 How long ago does the radiometric dating of lava place the age of eruption at this location?
Once you complete the EarthCache requirements you can post your find without delay, as per the EarthCache guidelines. You will also need to verify your find by sending me a message and provide your answers to the questions.
For a link to my profile, click here - Na'wal
Thanks for visiting this Earth Cache. Hope you enjoy the location.
Feel free to attach photos to your log (optional) but please don't post any spoilers.
References ~ Wikipedia, VRO