What is the oldest volcano in the world.

rocky Ryan

Dear Ryan,

I've been wondering when someone would ask this question. I will not be able to give you a specific answer. Here's a few things for us to think about.

Old rocks, a billion years or more, tend to be beat up a bit (or more). They might be folded and faulted. The might have their original minerals replaced by a new set of minerals. The original volcanic edifice (stratovolcano, shield, etc.) probably won't be recognizable. None of these would stop a volcanologist from getting all the information she could out of the rock. An age can be determined and the chemistry can tell a lot. Sometimes pillow lava or ropy pahoehoe lava can be found.

Volcanologists have found old volcanic rocks in the cratons of most continents. Here's a brief list of places and ages: 

Canada: 3.5 to 2.8 billion years
Rhodesia (Zimbabwe): 3.4 billion years
South Africa: 3.3 billion years
West Australia: 2.8 billion years
West Australia: 3.1 billion years

3.5 billion years seems old to me. Since the oldest known rocks are 3.96 billion years old, you might ask why there are not any volcanic rocks older than 3.5 billion years. There might be and they have not been found (funding mapping projects is not very popular these days). More likely they did exist and were changed by high pressure and temperature into metamorphic rock. If I spent a day in the library I could probably find the age of the oldest metamorphic rock that used to be volcanic. But I'm happy with 3.5 billion years. Hope you are too.

Thanks for a good question.

Steve Mattox, University of North Dakota

Sources of Information:

Palfreyman, W.D., 1984, Guide to the geology of Australia: Bureau of Mineral Resources, Geology, and Geophysics Bulletin 181, 111 p.

Wilson, H.D.B., and Morrice, M.G., The volcanic sequence in Archean shields: The Geological Society of Canada Special Paper Number 16, p. 355-374. 

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