For this exercise you will examine samples from three different types of pyroclastic deposits. This week you will use a set of stacked screens with 1 phi intervals to analyze the grain-size distribution more accurately.  We will not use a mechanical shaker because the samples were small and do not necessarily represent a good sampling of the deposit.  However, sieving by hand shaking should allow you to identify the main characteristics of the deposits and quantify the mean grain size and the sorting coefficient for each sample.

    You should work in groups to perform the analyses and tabulate the data.  Then you will individually plot the histograms of the samples and determine the Inman statistics using the SFT code.

Use a stereo microscope to examine the 0 phi and 2 phi fractions of each sample to estimate the percentages of the various components.

Finally you should compare the results from this study with those obtained by visual inspection in your last lab and record any new conclusions that you reach, if appropriate.

The data set consists of these three samples:

1. COT-0301A from Cotopaxi Volcano, Ecuador
2. HUA-0201 from Hualca Hualca volcano, Peru.
3. IGN-0203 from an area to the NW of Chachani Volcano, Peru.