Deep inside Earth, heat and pressure cause rocks to melt, forming liquid rock or magma. At this depth, some of the rocks would be already liquid, and others would need a small rise in temperature or small drop of pressure to melt and form magma. Decompression melting occurs thus when pressure decreases causing those igneous rocks to melt. Magma later rises towards the surface since it is lighter than the rocks that surround it. It takes several thousands or even millions of years for this magma to reach the Earth's surface and flow out of an opening called a vent. Once magma reaches the surface, we call it lava. This lava cools and becomes thus solid, forming layers of igneous rock around the vent. The steep-walled depression around a volcano's vent is the crater.
Questions:
1- What is magma composed of?
2- What factors influence the difference in magmas (highly fluid, pyroclastic ash...)?
3- Why does a descrease in pressure cause rocks to melt?
References:
- Grotzinger, J., & Jordan, T. (2010). Volcanoes. In W.H. Freeman and Company.
- Weston, M. (n.d.). Volcanoes. Retrieved from www.volcanoes.com
- Dr. Camp, V. (n.d.). How volcanoes work. Retrieved from http://www.geology.sdsu.edu/how_volcanoes_work/Home.html
1)Magma, also known as liquid rocks is composed of melted rocks as a result of heat and pressure.
ReplyDelete2)Some of the factors that differentiate magma apart are, its temperature, water content, crystallinity, viscosity, or the mixture of two different types of magma.
3)Decreasing the pressure causes only igneous rocks to melt and thus transform into magma. This type of melting is known as decompression melting.
1. The magma is formed as the heat and pressure melt the rocks turning them into magma.
ReplyDelete2. The temperature of the magma and its viscosity cause the difference in magmas.
3. It is an axiom in physics that the decrease in pressure increases the volume, which means that solids increase in volume to form liquids (rocks melt to magmas) when exposed to less pressure.