Do all volcanic eruptions feature rivers of lava?

Answer 1

No. Rivers of lava are characteristic of non-explosive (Hawaiian) or mildly explosive (Strombolian) eruptions. Volcanoes can erupt in a number of manners.

Vulcanian eruptions produce clouds of ash and eject large chunks of rock called volcanic blocks. They sometimes feature a noticeable shockwave. Pyroclastic flows may sometimes occur.

Peléan eruptions produce massive clouds of material, primarily in the form of pyroclastic flows, the deadliest hazard produced by volcanoes. These flows are avalanche-like masses of superheated ash, rock, and gas that race down the sides of a volcano.

Plinian eruptions are the most violent. They are noted for producing vertical columns of ash that tower miles into the sky. These columns eventually spread out and rain ash on the surrounding countryside. Plinian eruptions often produce pyroclastic flows. In the largest events, termed Ultra Plinian, these flows may dwarf those of Peléan eruptions.

Phreatic eruptions occur when groundwater comes in contact with magma or hot rocks and flashes to steam. Clouds of ash often result, formed from rock blasted by steam explosions rather than from fresh magma.

Submarine eruptions occur when lava is erupted underwater. The surface of the lava cools so quickly that it only flows a short distance before crusting over. It then breaks through this crust and repeats the process. This creates a series of lobes in a type of formation called pillow lava.

Surtseyan eruptions occur when molten rock erupts in shallow water. Steam explosions result, producing fountains of ash, rock, water, and steam.

Dome-building eruptions occur when a volcano erupts dacite or rhyolite lava. These sorts of lava are so viscous that often they do not flow away from the vent, but rather pile up into a rocky dome. In some cases a dome may collapse, producing pyroclastic flows.