Definition of magma in English:



  • Hot fluid or semifluid material below or within the earth's crust from which lava and other igneous rock is formed by cooling.

    • ‘Two years ago the magma was close enough to the crown of the volcano to be seen clearly from the air.’
    • ‘Until the rocks crystallized, uranium atoms could move freely through the molten magma from which they formed, and decayed uranium could be replenished.’
    • ‘As old oceanic crust was consumed in the trenches, new magma rose and erupted along the spreading ridges to form new crust.’
    • ‘Massive sulfide deposits may also form in other settings where water circulates in rocks near cooling magma.’
    • ‘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.’
    • ‘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.’
    • ‘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.’
    • ‘Igneous rocks are those that have formed from molten magma.’
    • ‘Scientists believe that diamonds ascend to the earth's surface in rare molten rock, or magma that originates at great depths.’
    • ‘In other words, the magma is squeezed upwards as thin sheets through long, narrow fractures.’
    • ‘Injections of new batches of mafic magma have been important for triggering dacitic eruptions.’
    • ‘From beneath the dome, the magma could combine with pressurized gases and steam to trigger an eruption, Pierson said.’
    • ‘This magma is rich in carbon dioxide gas, which produces explosive eruptions.’
    • ‘Crystals of the mineral were then carried in suspension by the upward-moving magma and forced toward the center of the flowing slurry.’
    • ‘Magmas concentrate metals, and magma fluids traveling into the surrounding wall rock plant the seeds for mineral growth.’
    • ‘The continuing uplift of the caldera rim can be explained by the restricted size of the magma's exit route.’
    • ‘Melts form at the highest temperatures and lowest pressures resulting in large volumes of tholeiitic magma that form shield volcanoes such as Mauna Loa.’
    • ‘Normally magma would fill the crack and the adjacent plates would inch away by just that amount.’
    • ‘Prior to any volcanic eruption, magma wells up through the earth's crust via any weaknesses in the rock structure.’


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