![]() In fact, the composition of the magma, as well as its gas content, largely determines whether an eruption is explosive, and the magnitude of that explosivity. Yet many aspects of eruptions are actually controlled by magma chemistry. Volcanic eruptions are inherently physical processes given that they are the emission of gas, magma, and rock from within the Earth. ![]() Magma typically begins to crystallize while they are being stored in magma chambers, forming a liquid-crystal mush.Įruptions from a shallow magma body may be triggered by injection of more magma into the chamber, by overpressure from increased volatile (gas) content, or by some other factor. Shallow magma chambers may form in regions of neutral buoyancy, i.e., areas where the pressure within the magma body equals the pressure outside it. Sometimes it pools at the base of the crust, and other times it continues to rise to form magma chambers. It moves in slow-moving balloons or diapirs or in planar fractures (dikes). Once magma is generated, it rises buoyantly because it is lighter than the surrounding rock. ![]() The heat that causes the partial melting comes from several sources most importantly, from decay of radioactive elements, such as uranium, thorium, and potassium. Instead, magma produced from partial melting of the upper mantle. There are also no permanent pools of melted rock found within the crust or mantle. The melted rock (magma) that is erupted in volcanoes does not come from the Earth’s core or even from deep within the mantle. Whether active or ancient, volcanic landforms found in national parks result from their eruption dynamics, with the volcanoes themselves and the lava flows and other deposits they leave behind serving as tangible evidence of the volcanic processes that formed them. The Valdez Caldera erupted 1.25 million years ago.Capulin Volcano erupted just over 54,000 years ago.Mount Mazama exploded about 7,550 years ago to form Crater Lake. ![]() Today, these mountains evoke peace and serenity that belies the violence in their history. Volcanoes in many other parks erupted in the even more distant past.
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