Question: How do mafic volcanic rocks get to Earth's surface? Need Assignment Help? Pressure from overlying crust forces mantle magmas through cracks to Earth's surface. These magmas erupt out of volcanoes, cool, and solidify into rock. Pressure from overlying mantle forces crust magmas through cracks to Earth's surface. These magmas erupt out of volcanoes, cool, and solidify into rock. Heat from the mantle melts part of the lower crust to form magma, which rises to Earth's surface. These magmas erupt out of volcanoes, cool, and solidify into rock. Heat from the lower crust melts part of the mantle to form magma that rises to Earth's surface. These magmas erupt out of volcanoes, cool, and solidify into rock.