Magma is a liquefied mixture of rock, crystals and dissolved gas. While this fits the general description of magma, it has three distinct observed types: basaltic, rhyolitic and andesitic.Know More
Magma types tend to consist of mixtures of silicon dioxide, or molten sand/glass, combined with a varying mix of iron, magnesium, calcium, sodium and potassium, according to Tulane University. This variance is what determines magma's classification. Basaltic magma is high in iron, magnesium and calcium but low in sodium and potassium, while rhyolitic magma is the opposite.
Gases in magma consist mostly of water and carbon dioxide, with small amounts of sulfur, chlorine and flourine gas. This gas is kept dissolved within the magma due to the high pressure involved but escapes to the surface should the pressure on the magma be relieved. Gases emerging from magma are what create its volatile behavior, and in turn, they are largely what cause eruptions. The gas content in different varieties of magma can vary, with rhyolitic magma carrying a very large measurable amount.
Magmas of different types have varying properties, such as viscosity and the observed temperature at which they commonly erupt. Magmas that have higher viscosity have a greater chance to erupt at lower temperatures due to the amount of gas found within them, for instance.Learn more about Volcanoes
A volcanic neck forms when lava inside a caldera cools after magma stops feeding the mountain, and then the outside of the extinct volcano erodes after millions of years. The cooled lava remains intact because it is harder than the surrounding rock that eroded. Perhaps the most famous volcanic neck in the United States is Devil's Tower in Wyoming.Full Answer >
The formation of volcanic islands occurs as tectonic plates move over fixed "hot spots" in the ocean, where underground rock melts to form magma. This magma rises to the surface to become lava that cools and builds up mounds, which eventually break through the surface of the water to form islands. The process takes thousands of years and involves hundreds of eruptions, explains Live Science.Full Answer >
The volcano Popocatépetl produces magma that is primarily andesite mixed with some dacite as of the current eruption cycle including 2015. This active stratovolcano, the second tallest peak in Mexico, has erupted primarily andesitic magma for most of its history.Full Answer >
Volcanic eruptions occur when magma builds up beneath the Earth's crust and forces its way to the surface. Natural vents in the crust allow magma passage to the surface, and eruptions occur when the magma that forms is less dense than the material above it, causing it to flow upward. In some cases, this flow is slow and steady, but it can also be rapid and violent.Full Answer >