Part 1 - Download the data
- Go to the PETDB database.
- Click on the "Build Query" button on the sidebar to the left.
- "SET" the Tectonic Setting. Choose "SPREADING_CENTER" from the list which pops up, folllowed by "Apply".
- Now "SET" the Sample Characteristics. Choose "FRESH" under Alteration.
Question 1. Why would limiting your query to fresh samples be important? How common would fresh samples be from the ocean floor?
- Under Rock type, click on "igneous:volcanic:mafic", followed by "Add All >>", and then "Apply". This should zero in on the basaltic rocks we are interested in for this exercise.
- When the database has modified your query, select "Continue to Data Selection". Ignore the warning that pops up telling you have have selected alot of samples: your computer can handle it!
- When the next page comes up, click the radio buttons next to "precompiled data" and "Samples with all selected elments", and then click "glass analyses". Before proceeding, wait until the database has stopped working to modify your query. While you wait, answer this question:
Question 2. What do you think was the reason for selecting only glass analyses?
- Next, on this same page, select the following data to include in your spreadsheet: SiO2, Al2O3, FeOt (total Fe expressed at FeO), MgO, CaO, Na2O, and K2O. Now you can finally "Submit" to complete your query. It will take some time to download all of those samples!
- When the next page pops up, click "Download" to download an Excel spreadsheet of the data. This will take some time as well.