[Music] [Music] partial melting heat transfer decompression melting at flux melting magma is a molten or semi-molten natural material that is found beneath the surface of the earth it creates igneous rocks when solidified that is found on the surface of the earth another it is a mixture of molten rock minerals and gases it is usually made up of hot liquid base called the melt its temperature ranges from 700 to 1300 degrees centigrade or degrees celsius [Music] the source of heat from within is high enough [Music] next is magma and lava so how can we differentiate the two terms magma and lava are both molten rocks the only difference is the location so scientists use the term magma for molten rock that is underground or found in the magma chamber of a volcano and lava for molten rock that breaks through the earth's surface are found on the surface of the earth once the volcano perhaps a process under the earth's grass where formation and movement of magma occur is what we call magmatism next is where does the formation of magma takes place so it happens in the asthenosphere so it is the lower part of the earth's grass and in the upper portion of the mantle so remember that the earth has three parts the crust mantle and core so asthenosphere is found between crust and mantle so again it is the part of the earth where the formation and movement of magma takes place three composition of magma so take a look on the pie chart and it presents the elements present in magma so the composition of magma depends on the rock it was formed from and the conditions of melting so magmas derived from the mantle have higher levels of iron magnesium and calcium but they are still likely to be dominated by oxygen and silicon in our pie chart it shows that the oxygen is the most abundant element in magma so it comprises less than half or 46.6 of the total composition of magma followed by the element silicon at just over one quarter or has 27.7 percent we also have aluminum with 8.1 percent iron with five percent three point six percent for calcium sodium has two point eight percent potassium is 2.6 and the element which has the lowest amount in magma is magnesium with 2.1 percent so again so these are the elements found in magma [Music] next is the ways to generate magma so molten rocks undergo the process called partial melting from the word it's a parshan hindi totally battle so it is mainly because of the components of the rocks so partially all of the igneous rocks that we see on earth are derived from magmas that form from partial melting of existing rock so either in the upper mantle or the crust so partial melting is what happens when only some parts of a rock melt it takes place because rocks are not pure materials so most rocks are made of cebural minerals each of which has a different melting temperature or it melts at different temperatures and these substances have their own melting point as nothing melting point temperature is a substance since most of the minerals have different melting points indirect sabesabai natuku now and manga minerals partial melting so i have here an example example i am once so the wax in a candle is pure so if you put some wax into a warm oven at certain temperature and leave it there for a while so what do you think will happen so it will soon start to melt and that is complete melting and not partial melting since the wax in a candle is pure so masma bilisha natuna or natuna so if instead you took a mixture of wax plastic aluminum and glass and put into the same warm oven the wax would soon start to melt perro and plastic aluminum and glass would not melt and that's exactly partial melting and the result would be solid plastic aluminum and glass surrounded by liquid wax since she walks long and pure materials milk so of course partial melting in the real world isn't exactly the same as in our example so racks are much more complex than the four component system used in the example and the mineral components of most rocks have more similar melting temperature so two or more minerals are likely to melt at the same time to varying degrees so another is when rocks melt the process takes thousands two million years not minutes or an hour it took in the example last are the conditions for melting of rocks to occur so first one so there must be an increase in temperature next is the decrease of pressure and last one is the addition of volatiles let us start with increase in temperature so as magmaris says we all know that it is very hot so its temperature is around 1200 degrees celsius and enough to melt the rocks it touches such as quartz and feldspar that begins to partially melt at around 650 to 850 degrees celsius when heat is transferred from molten rocks to the earth's cold brush this process is called heat transfer and it happens in convergent boundaries where tectonic plates are crushing together second one is the decrease of pressure so rocks in mantle remains solid when exposed to high pressure so what happens if the pressure is being reduced so during convection rocks tends to go upward and triggers the melting of magma and this is known as decompression melting so this process occurs at the mid ocean ridge and underwater mountain system for our last condition is the addition of volatiles so this process is called flux melting so it occurs when water and carbon dioxide is added to hot rocks so these compounds cause the rock to melt at lower temperature so this creates magma in places where it originally maintained a solid structure and occurs around subduction zones again here are the conditions for melting of rocks first there must be an increase in temperature so the process is called heat transfer and it happens in the convergent boundaries next decrease of pressure so it occurs in the mid ocean ridge and the process is called decompression melting and last is the addition of volatiles the process is called flux melting and it occurs in the subduction zones