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Then what exactly is it...........

 

 

Molten basalt containing bubbles of gas... 

 

More accurately it is molten basalt with gasses dissolved in the lava that fizz out when it comes to the surface and the pressure is released. Much like soda pop...  

Edited by Moontanman
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Molten basalt containing bubbles of gas... 

 

More accurately it is molten basalt with gasses dissolved in the lava that fizz out when it comes to the surface and the pressure is released. Much like soda pop...  

This sounds like a description of pumice rather than lava.

 

Lava is a much broader term and simply means rock extruded from a volcano that is hot enough to be fluid or semi-fluid. Basalt is one type of lava but there are many others too, such as andesite or rhyolite. And the amount of gas in lava varies very widely as well. For example in fluid lava of the type often extruded from Hawaiian volcanoes, there is almost no gas present. An example of the solid rock formed by cooling basalt with no gas in it is obsidian - a black glassy material, very different indeed from pumice. 

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This sounds like a description of pumice rather than lava.

 

Lava is a much broader term and simply means rock extruded from a volcano that is hot enough to be fluid or semi-fluid. Basalt is one type of lava but there are many others too, such as andesite or rhyolite. And the amount of gas in lava varies very widely as well. For example in fluid lava of the type often extruded from Hawaiian volcanoes, there is almost no gas present. An example of the solid rock formed by cooling basalt with no gas in it is obsidian - a black glassy material, very different indeed from pumice. 

 

 

Lava can contain various amounts of volatile compounds as well as consist of various materials, until the pressure is relieved it is molten rock, just the way soda pop is a liquid until you release the pressure and it becomes foam.. 

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Lava can contain various amounts of volatile compounds as well as consist of various materials, until the pressure is relieved it is molten rock, just the way soda pop is a liquid until you release the pressure and it becomes foam.. 

This is not true of lava in general. As I said before, plenty of lava has relatively little dissolved gas in it, in which case the "soda pop" analogy is irrelevant and confusing.

 

The "soda pop" analogy is used to explain how pyroclastic flows form, i.e. by explosive release of pressure and consequent fragmentation of the lava into an expanding cloud of gas and particles.

 

A lava flow just flows like a river of treacle (pahoehoe) or like a landslide of blocks of clinker (aa), with little or no evolution of gas.

 

Forget the gas. It is not part of the explanation of a lava flow. More details here: https://en.wikipedia.org/wiki/Lava

Edited by exchemist
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