Volcano Math

I was listening to Planetary Radio the other night and they had an interesting interview with Rosaly Lopes, a researcher at the Jet Propulsion Laboratory who has discovered more volcanoes than anyone else. Her discoveries were of volcanoes on other planets and satellites. This interview got me thinking -- just how many active volcanoes are there on Earth and where are they? This looks like a good job for Excel and pivot tables.

Time to go to the web and start hunting around. Very quickly I encountered a number of web sites (e.g. here and here) with lists of "active" volcanoes. Depending on your definition of active volcano, I have found sites that list between 400 and 1500 items. For no particular reason, I ended up focusing on the Volcano World web site from Oregon State University. They have a list of 430 volcanoes that was easy to import into Excel and will give me a feel for the number of volcanoes and where they are. Once the list is in Excel, we can start to ask questions about the data and get some answers.

One other quick point -- we have not discovered all of the volcanoes yet. For example, you occasionally hear of a previously unknown underwater volcano being discovered. So these lists do change occasionally. Also, the lists sometimes combine two nearby volcanoes in a single entry, like Tanaga and Takawangha. So you may see different numbers of volcanoes on different lists.

My question was about the number and location of the volcanoes. I also want to know what countries have the most volcanoes. I used a pivot table to divide the volcanoes up by country. Table 1 shows the results.

Table 1: Summary of Volcano Counts By Country.
Country Volcano Count
USA 81
Russia 55
Indonesia 45
Japan 40
Papua New Guinea 17
Ecuador 12
Philippines 11
Nicaragua 9
Ethiopia 9
Vanuatu 9
Chile 8
New Zealand 8
Kenya 7
Mexico 7
Guatemala 7
Italy 6
El Salvador 5
Greece 5
Spain 5
Iceland 5
Costa Rica 4
Australia 4
France 4
United Kingdom 4
Mariana Islands 4
Colombia 3
Tanzania 3
Portugal 3
Eritrea 2
Netherlands 2
Pacific Ocean 2
Peru 2
India 2
Cape Verde Islands 2
St. Kitts and Nevis 2
Philippines 2
Turkey 2
Democratic Republic of Congo 2
Cameroon 2
Azores (Portugal) 2
Solomon Islands 2
Iran 2
Ethiopia,Kenya 1
South Atlantic Ocean 1
Multiple Countries 1
Norway 1
Libya 1
Congo/Rwanda 1
Canary Islands (Spain) 1
Argentina 1
Comoros 1
Chad 1
Lesser Sunda Islands 1
Azores 1
St. Vincent 1
Antarctica 1
Tonga 1
Chile/Argentina 1
Uganda 1
Chile/Bolivia 1
Galápagos Islands 1
Rwanda, Congo 1
Grenada 1
China 1
Grand Total 430

I was surprised that the US had so many volcanoes. Let's take a closer look at the volcano count in the US by state. Just out of curiosity, I will separate out the Aleutian Islands from Alaska so that I can see where the volcanoes are in that area. Table 2 shows this data.

Table 2: Summary of Volcano Counts By State and Islands.
State/Region Volcano Count
Alaska 21
Aleutian Islands 18
Oregon 14
Hawaiian Islands 7
Washington 5
California 4
Arizona 4
Other Pacific Islands 2
Wyoming 2
New Mexico 2
Idaho 2
Grand Total 81

Now I want to look at the distribution percentage of volcanoes by state. I will recombine the Aleutians with Alaska. I will list non-state volcanoes in the "other Pacific Islands" category (e.g. Guguan and Pagan Islands). Table 3 shows this data.

Table 3: Summary of Volcano Percentages By State and Islands.
State/Region Volcano Percentage
Alaska and Aleutians 48.15%
Oregon 17.28%
Hawaiian Islands 8.64%
Washington 6.17%
California 4.94%
Arizona 4.94%
Other Pacific Islands 2.47%
Wyoming 2.47%
Idaho 2.47%
New Mexico 2.47%
Grand Total 100.00%

So nearly half of the US volcanoes are in Alaska and the Aleutians.

What I learned here was that the US has many more volcanoes than I would have thought and nearly half of them are in Alaska. I also showed that pivot tables are great for slicing up data like this.

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4 Responses to Volcano Math

  1. CC says:

    Welcome to the "ring of fire"... Alaska, Washington, Oregon, and California are 4 of the top 5 in your state-by-state list, and with Hawaii (which *is* a volcano) those 5 states hold about 85% of the US volcanoes 🙂 British Columbia and Yukon Territory are on the ring of fire too, with volcanoes of their own.

    I'm surprised none of them are on the list you found. Maybe it's in the definition of "active", but even so, BC has a few that fall within the "erupted in the last 1000 years" threshold, and the Global Volcanism Program definition for "active" is one that erupted in the last 10,000 years.

    • mathscinotes says:

      It is all about the definition of active. If I look at the lists with 1500 volcanoes, BC and Yukon are represented. I was surprised at the number of volcanoes in the US. When I was a kid, I was told that the US volcanoes were just the Hawaiian Islands and Lassen Peak in California. Now we recognize a large number of volcanoes. Funny how these things change.

  2. Dave Spencer says:

    curious to see how the distribution changes if you were to use all 1500. Love the site by the way!

    • mathscinotes says:

      I actually have processed the data for 1500 volcanoes and I will post it soon. In fact, just the other day one of those volcanoes on the 1500 list and not on the 400 list erupted. So it does happen.


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