GEOLOGY

Detailed explanation-1: -As magma approaches the surface, the pressure exerted on it decreases. Gas bubbles start to form, and the more gas there is in the magma, the more bubbles form. If the gas content is low or the magma is runny enough for gases to rise up through it and escape to surface, the pressure will not become excessive.

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.

Detailed explanation-3: -When magma flows or erupts onto Earth’s surface, it is called lava. Like solid rock, magma is a mixture of minerals. It also contains small amounts of dissolved gases such as water vapor, carbon dioxide, and sulfur. The high temperatures and pressure under Earth’s crust keep magma in its fluid state.

Detailed explanation-4: -Gases in Magmas Gas gives magmas their explosive character, because volume of gas expands as pressure is reduced.

Detailed explanation-5: -Magma is a liquid rock that is below the surface of Earth. Magma is typically located within the crust and in the upper mantle. Magma is liquid rock found within Earth.