Why does one volcano ooze lava while another buries a whole city? The difference lies in magma viscosity and dissolved gas, not in how much magma there is. Runny basalt gives low fountains and gentle flows, while stiff magma corks the conduit until it blows out as a Plinian ash column 20 to 40 km high. The real killer is not the lava but the pyroclastic flow, a mass of gas and ash near 700°C racing down the flank.
Why does one volcano ooze lava while another buries a whole city? The difference lies in magma viscosity and dissolved gas, not in how much magma there is. Runny basalt gives low fountains and gentle flows, while stiff magma corks the conduit until it blows out as a Plinian ash column 20 to 40 km high. The real killer is not the lava but the pyroclastic flow, a mass of gas and ash near 700°C racing down the flank.
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