Magma | Science for ACT PDF Download

Introduction

• Magma, an intensely hot blend of liquid and semi-liquid rock situated beneath the Earth's surface, constitutes a significant portion of the planet's mantle. This molten substance, characterized by its high temperature and mineral composition, primarily comprises silicon dioxide along with traces of dissolved gases such as water vapor, carbon dioxide, and sulfur. Maintained in a fluid state by the intense temperatures and pressure beneath the Earth's crust, magma can breach the surface through fissures or apertures, resulting in volcanic eruptions, where it transforms into lava upon exposure to the Earth's surface.
• Earth's layered structure, encompassing the inner core, outer core, mantle, and crust, accommodates the circulation of magma. Comprising a mixture of minerals, magma exhibits diverse compositions, notably distinguished into three fundamental types: basaltic, andesitic, and rhyolitic, each characterized by specific mineral distributions. Basaltic magma, rich in iron, magnesium, and calcium but deficient in potassium and sodium, operates within a temperature range of approximately 1000°C to 1200°C (1832°F to 2192°F). Andesitic magma, with moderate levels of these minerals, maintains temperatures ranging from about 800°C to 1000°C (1472°F to 1832°F). Conversely, rhyolitic magma, abundant in potassium and sodium yet scarce in iron, magnesium, and calcium, operates within a temperature range of about 650°C to 800°C (1202°F to 1472°F). The temperature and mineral composition significantly influence the flow characteristics of magma.
• The viscosity, or thickness, of erupting magma profoundly influences the morphology of volcanoes. Volcanoes formed from highly viscous magma tend to exhibit steep slopes, while those originating from more fluid magma display flatter profiles, reflecting the ease of magma flow.