The Products of Volcanic Eruptions


1. Steam and Gases Steam and poisonous gases such as chlorine are often ejected in volcanic eruptions. Hot and heavy gases sometimes tumble down the sides of volcanic mountains in the form of nuées ardentes (‘fiery clouds’). Such clouds travel at up to 10 metres per second. They bring instant death to anyone in their path.


2. Ash Fine ash may also be ejected. This was once rock that was pulverised by the violent explosion. It can be thrown several kilometres into the sky and may be carried away by the winds.


A volcano in the Caribbean Island of Montserrat spews out acid lava and volcanic cloud


4. Lava One of the main products of volcanic eruptions is lava, which is magma after it reaches the surface and releases its gases. Acid lava is produced at destructive plate boundaries. It is sticky and flows very slowly. Basic lava is produced at constructive plate boundaries. It is runny and can flow quickly and over greater distances.


3. Pyroclasts Rock particles are also hurled into the air. These particles, in general, are called pyroclasts or tephra, though they may sometimes have a specific name. Some pyroclasts, for example, are about the size of a pea and are called cinders. Others are thrown into the air as spatters of boiling mud, but cool instantly to fall as red-hot pieces of rock. They are called volcanic bombs and can range from only 3cm across to the size of a large car.


5. Lahars Lahars are rivers of mud that flow down the sides of volcanic mountains. They are made up of soil or rock fragments.


Learn more


about lahars on page 24.


16


A destructive lahar on Montserrat Island


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