The Geomorphology of the Moon Mountain Area We started off at school, to head out to Usfan. Usfan is an area north east of Jeddah. In this project I am mainly going to talk about the history and the geology of the region. We set up camp just after Moon Mountain. At this site there were many apparent geographic features such as batholiths, dykes and huge amounts of weathering.
The origins of the red sea date back to about 35 million years ago which in geographical terms is a very recent event. The pre-rifting stage commenced with an asthenospheric hot spot forming under the Arabian plate. Asthenospheric hot spots are areas underneath the lithosphere where molten rock builds up and causes crustal doming, uplifts, faulting and volcanics.
As shown in the diagrams above, we see the fist stages of the rifting of the Red Sea. Tectonic movement has elevated the west side of Arabia and depressed the east.
Early rifting commenced in the late Oligocene to middle Miocene period which is about 15 million years ago. After this widespread igneous rock activities took place including basaltic lava flows. Dyke swarms were injected in to the continental crust in zones of 5 to 10 kilometers wide. As shown in the diagram below The pictures below show examples of dykes that have been injected into the continental crust As u can see clearly there is a darker colored line of rock within the hill. This is the dyke. Below we can see on the hill that the Dyke splits up which has been formed in the early rifting of the Red Sea.
These Dykes have also crossed over faults and have been shifted. There is was an absolutely amazing example of this at our site as shown below, the student representing the dyke.
Sea Floor spreading only started about 5 to 6 million years ago. And ever since then the Red Sea until now continues to move at rates of 0.5cm to 1cm per year.
In the area we were in called Usfan there were many great batholiths to be seen due to the uplift and weathering. Now the granite rock that used to be under the earth with tremendous pressure has broken the surface. But now due to the exposure the batholiths have been subjected to weathering such as exfoliation or also know as "onion skin weathering". In the pictures below we can see how these huge batholiths are being eroded The granite being subjected to hard core weathering has become weak and easily broken by human force. As shown above our teacher (Mr. Bradley trying to show off) can easily break of layers of the batholith. The granite its self is also subjected to chemical weathering, such as the mica which turns black due to rotting and the feldspar turn into a pinkish or fools gold looking mineral. Below we can see the mica turning black, and the while rock will eventually become red mud, which is being used in the area to make red bricks.
While below, we can see a perfect sample of the feldspar mimicking the fools gold appearance.
Mechanical weathering is the disintegration of rock into smaller particles by mechanical processes but without any change in the chemical composition of that rock. Its most occurant in areas with minimum vegetation such as deserts high mountains and arctic conditions. Physical weathering is apparent usually produces sands like the sand in this sand dune Biological weathering is the breakdown of rocks such as in Physical weathering, but it is done my living plants and animals. A perfect example is shown in the picture below as the tree's roots dig into the rocks splitting them apart.