increasing something causes its value to become higher & extreme means very high in value ->  increasing something causes that something to become extreme  increasing something causes that something to become extreme & exposure to extreme heat and pressure changes / metamorphoses sedimentary / igneous rock into metamorphic rock ->  exposure to increased pressure metamorphoses sedimentary rock into metamorphic rock  exposure to increased pressure metamorphoses sedimentary rock into metamorphic rock & shale is a kind of sedimentary rock ->  exposure to increased pressure metamorphoses shale into metamorphic rock  exposure to increased pressure metamorphoses shale into metamorphic rock & slate is a kind of metamorphic rock -> exposure to increased pressure metamorphoses shale into slate