Extension Unit - Volcanoes

This exercise introduces you to some of the volcanoes of South America. In doing so it asks you to explore some basic questions about both South America and about volcanoes, and invites you to ask questions based on the database provided, and to add to it.
 

The database is provided as an Excel spreadsheet. This means that the program can be used to group parts of the database together, to put the records into order, and to produce graphs of the data.

It is important when using a database to make sure that it is large enough to contain a range of data. Otherwise a single record could alter the conclusions drawn simply because it would represent too large a proportion of the total. If there are only 24 records in a database, every record is 4.2 %; the bigger the database, the more realistic the conclusions which can be drawn from it.

2. From the South American database, answer the following questions ;

a. How big is the database ?

Answer ; It has __ records, each with __ fields.

b. How many volcanoes does Colombia have ?

Answer ; From the information provided, Colombia has ___ volcanoes.

c. Which is the highest volcano in South America ?

Answer ; From the information provided. ___ is the highest volcano in South America.

d. Why does Brazil not have any volcanoes ?

Answer ; (Clue ; think about plate boundaries)

3. To us the power of Excel, it is possible to ask it to do certain tasks which it would take a lot longer to do without the program

a. Group the volcanoes of each country together.

i. Click on the cell at the top of the Country column ("B"). This highlights the column you will be working with.

ii. Click on Data, then Sort (from the top menu bar).

iii. Notice that this will only sort that column, not the whole table, so when the Sort warning comes up to tell you this, click on "Continue with the current selection"

iv. This allows you to total the number of volcanoes in each country very quickly . If the totals were put in a separate table, Excel could be used to produce a graph of them .

b. Find out the average height of South American volcanoes

i. Remember that Average height = total of all the heights divided by the number of volcanoes

ii. In a cell under the Height column, cell E28, put the total height of all of the volcanoes, by clicking on the ? symbol for the top menu bar. This is a Greek letter, Sigma, and means "Add up". If you insert it into a cell below a column in a spreadsheet it will automatically add up all the values in that column.

Notice what it is doing, by looking at the Formula bar at the top of the page

Click on the Return key to fix the value in the cell.

iii. In the cell beneath this total, i.e. cell we want to calculate the average height of volcanoes in our database. To do this we must divide the total heights (which we have just worked out) by the total number of volcanoes.
To do this, put the cursor into cell F29, then type the following into the formula bar at the top of the page;

This divides the total in F28 by 24, the number of records.

c. Produce a scattergraph of the heights of South American volcanoes

The average you have just calculated does not give an indication of the range of heights. This can be shown on a graph.

i. Highlight the Height column, by clicking on the letter E at the top of it.

ii. Then click on the chart wizard icon in the top menu bar, and follow the four steps. Make sure that you remember to give your graph a title.

d. Add to the database of South American volcanoes by putting in information from other continents. This can be done from an encyclopaedia, or from a website such as Volcano World (www.volcano.und.nodak.edu/vw.html)

When you have at least 50 records, this is the large enough to be able to start making more detailed enquiries, such as

Is the average height of extinct volcanoes lower than dormant ones?

e. It is, of course, possible to add another field such as "Number of fatalities" to the database.

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