GEOLOGY

Detailed explanation-1: -At convergent boundaries magma is formed where water from a subducting plate acts as a flux to lower the melting temperature of the adjacent mantle rock. At divergent boundaries magma forms because of decompression melting. Decompression melting also takes place within a mantle plume.

Detailed explanation-2: -Areas of lower pressure always have a lower melting point than areas of high pressure. This reduction in overlying pressure, or decompression, enables the mantle rock to melt and form magma. Decompression melting often occurs at divergent boundaries, where tectonic plates separate.

Detailed explanation-3: -This happens because different minerals have different melting temperatures. The melt is less dense than the surrounding rock, and will percolate upward without the source rock having melted completely. The result is magma with a different composition than the original rock.

Detailed explanation-4: -Because the mantle is composed of many different minerals, it does not melt uniformly. As minerals with lower melting points turn into liquid magma, those with higher melting points remain as solid crystals. This is known as partial melting.

Detailed explanation-5: -Magma is produced at convergent boundaries when water from a subducting plate acts as a flux, lowering the melting temperature of the nearby mantle rock. Magma forms at divergent boundaries due to decompression melting. Inside a mantle plume, decompression melting also occurs.