Definition of magma in English:


nounPlural magmata, Plural magmas

mass noun
  • Hot fluid or semi-fluid material below or within the earth's crust from which lava and other igneous rock is formed on cooling.

    ‘when red-hot magma comes into contact with seawater, an explosion results’
    count noun ‘basaltic magmas are normally expelled at the surface in a very hot and fluid state’
    • ‘As old oceanic crust was consumed in the trenches, new magma rose and erupted along the spreading ridges to form new crust.’
    • ‘Injections of new batches of mafic magma have been important for triggering dacitic eruptions.’
    • ‘This magma is rich in carbon dioxide gas, which produces explosive eruptions.’
    • ‘Melts form at the highest temperatures and lowest pressures resulting in large volumes of tholeiitic magma that form shield volcanoes such as Mauna Loa.’
    • ‘Vulcanites, such as basalt and fire opal, will be formed within erupted magma where cooling is rapid and only tiny crystals have the chance to form.’
    • ‘Crystals of the mineral were then carried in suspension by the upward-moving magma and forced toward the center of the flowing slurry.’
    • ‘From beneath the dome, the magma could combine with pressurized gases and steam to trigger an eruption, Pierson said.’
    • ‘Prior to any volcanic eruption, magma wells up through the earth's crust via any weaknesses in the rock structure.’
    • ‘Scientists believe that diamonds ascend to the earth's surface in rare molten rock, or magma that originates at great depths.’
    • ‘Two years ago the magma was close enough to the crown of the volcano to be seen clearly from the air.’
    • ‘Igneous rocks are those that have formed from molten magma.’
    • ‘Normally magma would fill the crack and the adjacent plates would inch away by just that amount.’
    • ‘Until the rocks crystallized, uranium atoms could move freely through the molten magma from which they formed, and decayed uranium could be replenished.’
    • ‘What they do know is that a ‘slow rise’ of magma is driving lava to the surface, which has created a new lava dome in the mountain's crater.’
    • ‘Dolerite is basaltic magma that solidifies rapidly in sills and dikes near the surface.’
    • ‘In other words, the magma is squeezed upwards as thin sheets through long, narrow fractures.’
    • ‘An aircraft will soon fly over the lava dome to test for the presence of carbon dioxide and sulfur dioxide, signs that magma might be building up.’
    • ‘The continuing uplift of the caldera rim can be explained by the restricted size of the magma's exit route.’
    • ‘Magmas concentrate metals, and magma fluids traveling into the surrounding wall rock plant the seeds for mineral growth.’
    • ‘Massive sulfide deposits may also form in other settings where water circulates in rocks near cooling magma.’


Late Middle English (in the sense ‘residue of dregs after evaporation or pressing of a semi-liquid substance’): via Latin from Greek magma (from massein ‘knead’).