Question

1 Explain the significance of low For content in lunar rocks for understanding the origin of the moon and earth
2 Explain the significance oh hornblende(amphibole) in volcanic rocks understanding the explosive style of eruptions of volcanoes in the"Ring of fore"?
3Three mechanisms that can produce compositional banding in banding in gneisses

Answer 1

Ans(1) : The lunar basalts have low content of silica around 50%. Not only ballasts but all the lunar rocks have low silica content. This is contrasting in nature to the earth's crust. It helps in understanding the origin of the moon and earth. Lunar rocks are usually found on the surface of moon and hence the low silica content will give significance of moon and earth. Moon rocks on earth come from some sources naturally as they fell down by some natural causes like meteor falling on earth.

Ans(2) : Hornblende is a rock constituent which has constituents of many igneous and metamorphic rocks. It has particles from different metamorphic rocks like gabbro, basalt, dolorite, gneiss and many more. It is the principles mineral of amphibole. It may be used in understanding explosive style of eruptions. Due to the volcanic eruptions there are constituents of different rocks present in the hornblende rocks. It alters easily to chlorite and epidote. More the variety of constituents present in the hornblende mire will the explosive nature of the volcano.

Ans(3) : Compositional banding is the the appearance of different layers. It is being seen in gneiss rocks. Not all rocks show compositional banding, it is being shown by some like kyanite gneiss, crystal of kyanite gneiss. The mechanism used in bending are :

• High pressure is being applied and then the layers are being formed.
• Temperature is being increased and due to that pressure is also increased resulting in the banding.
• Minerals are being arranged in different layers that appears to be as bands in cross section.